FOUS11 KWBC 020730
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
230 AM EST Tue Dec 2 2025

Valid 12Z Tue Dec 02 2025 - 12Z Fri Dec 05 2025

...Mid-Atlantic & Northeast... Days 1...

...Rapidly deepening coastal low will bring heavy snow to the
interior Mid-Atlantic and Northeast today/tonight...

Low pressure will move off the NC/VA coast this morning and then
track rapidly northeast along the coast, passing inside the 40N/70W
benchmark before lifting into the Canadian Maritimes by Wednesday
morning. The overlap of height falls, a coupled jet streak, and the
latent heat release along the offshore baroclinic gradient will
allow the low to rapidly deepen during this period, spreading
heavy precipitation and gusty winds into the Northeast.

As the low moves up the coast, persistent and impressive moist
isentropic ascent will surge a theta-e ridge northward to support
expanding heavy precipitation. The coincident WAA at 850mb will
produce additional ascent, with intensifying fgen driving some
banded precipitation, but also warm the column aloft as the surface
high pressure retreats rapidly to the east. The guidance has
trended just a bit warmer again overnight, and while most areas
along I-95 and points west will likely start as a brief period of
snow/sleet, any meaningful accumulation is anticipated only well
inland and at higher elevations, especially in southern and central
New England. The big cities from Washington, D.C. to Boston, MA may
start as snow before changing over to rain (and Boston may change
back to snow briefly before the system exits Wednesday morning).
However, well NW, WPC probabilities are high (>70%) for at least 6
inches of snow from the Catskills through the Berkshires, the
Worcester Hills, and across much of southern NH and ME (away from
the immediate coast) where locally as much as 12 inches is possible
(10-30% chance).

Additionally, while most of the freezing rain accompanying this
system is expected to wane before 12Z/Tuesday, an additional 0.1"
of ice is possible (10-30% chance) across the Central Appalachians
in the vicinity of Shenandoah NP.

Key Messages remain in effect for this system and are linked below
(Key Message #3)

...Northern to Southern Rockies... Days 1-2...

A shortwave digging south out of British Columbia into the
northwestern U.S. will be positioned across the interior Northwest
to begin the forecast period /12z Tuesday/. This shortwave will
continue to move southeast through Wednesday, and may become more
amplified as it drops through the Great Basin in response to
secondary vorticity maxima digging through its base. This will
result in a slowing and amplification of the trough, with
downstream ascent maximizing through height falls, PVA, and
downstream intensifying jet energy, especially as it approaches the
Four Corners Wednesday morning.

Available moisture will generally be modest as reflected by near-
normal PW anomalies, but the overlapped synoptic lift will be more
than sufficient to wring this out as periods of moderate to heavy
snowfall across much of the terrain. At the same time, a wave of
low pressure is progged to drop southeast coincident with the
shortwave trough, and a secondary front will also push south out of
Canada to cool the column while additionally leading to localized
upslope flow. Despite a shallow DGZ noted in regional forecast
soundings, the best ascent is progged to intersect within this
snow growth region to enhance snowfall, and this suggests a broad
swath of moderate snow is likely today and Wednesday across much
of the Rockies.

WPC probabilities D1 for 6+ inches are highest in the terrain above
5000 ft from the Salmon River/Sawtooth Range of ID through the
Absarokas, Little Belts, Tetons, and down into the Park Range and
other CO Rockies. During D2, the highest probabilities shift south
with the shortwave and increase, reaching above 80% for 6+ inches
along much of the Sangre de Cristos where locally 12+ inches is
likely. Additionally, as this shortwave digs south, some moderate
snowfall is likely along the I-25 urban corridor of Colorado,
bringing some notable snow to a region that has yet to experience
much so far this winter.

...Great Lakes & Northeast... Day 3...

A strong arctic front will race across the Great Lakes Wednesday,
likely reaching Upstate NY by Thursday morning before continuing
into New England and crossing offshore into the Atlantic Thursday
night. Environmental signals continue to appear favorable for snow
squalls along this front as it dives southeast, and the GFS and NAM
SnSQ parameter have both increased tonight, especially from western
PA through northern New England where a significant overlap of
0-2km fgen and SBCAPE as high as 200 J/kg exists in a region of
elevated low-level RH. This suggests increasing confidence in
linear snow squalls, especially Thursday. While snowfall
accumulations from this event will likely be minimal, brief intense
snow rates combined with gusty winds may create dangerous travel
across parts of the northern Great Lakes and interior Northeast.

Weiss

...Winter Storm Key Messages are in effect. Please see current
Key Messages below...

https://www.wpc.ncep.noaa.gov/key_messages/LatestKeyMessage_3.png

$$
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FOUS11 KWBC 030755
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
255 AM EST Wed Dec 3 2025

Valid 12Z Wed Dec 03 2025 - 12Z Sat Dec 06 2025

...Southern/Central Rockies... Days 1-2...

Shortwave which emerged from British Columbia Monday will continue
to track southeast across the Four Corners today while amplifying.
The guidance has trended a bit farther south and more amplified
with the evolution today, which should result in heavier snowfall
especially across the San Juans and Sangre de Cristos on D1.
Forcing for ascent downstream of this trough (in response to height
falls and modest divergence) will be enhanced by a strengthening
jet streak, especially tonight into Thursday morning, and periods
of impressive upslope flow as cold N/NE winds develop in advance of
an Canadian high pressure dropping into the Plains. Moisture within
the region is progged to be around to slightly below normal as
reflected by NAEFS ensembles, but the impressive overlapping ascent
will still maximize favorable to support heavy snow, especially
above 4000-5000 ft, with snow levels falling in conjunction with
waning snowfall intensity. WPC probabilities, especially across the
San Juans and Sangre de Cristos, have increased tonight, and now
feature a high risk (>70%) for more than 12 inches in the higher
terrain of these ranges. Into the lower terrain, WPC probabilities
indicate a moderate threat (30-50%) for at least 4" along the I-25
urban corridor, with locally more than 6" in the higher terrain of
the Raton Mesa and southern Palmer Divide.

...Great Lakes & Northeast... Days 1-3...

Progressive flow across the Northeast will manifest in response to
a large gyre centered near Hudson Bay, which will shed periodic
shortwaves from the Great Lakes through the Northeast leading to
occasional enhanced ascent and lowered heights throughout. In
response to this evolution, the period will remain active through
LES and arctic fronts, and multiple rounds of snowfall, sometimes
heavy, are expected.

The first event will be associated with an arctic cold front
dragging southeast beneath a shortwave aloft. This front will
likely move rapidly across the Great Lakes today, and then across
the Northeast Thursday. Along and ahead of this front, the
environment continues to suggest an increasing threat for snow
squalls, especially across PA/NY and New England on Thursday. The
NAM SnSq parameter continues to be more aggressive than the GFS,
but the antecedent low-level environment ahead of the front appears
favorable for squall development. With 0-2km fgen maximizing along
the front into elevated RH and SBCAPE as high as 300 J/kg,
widespread linear squalls could result. Upstream into MI the threat
is not as high on D1, and although isolated squalls could occur,
the greater risk will be D2 in the Northeast. While total snowfall
will be minimal in any squall, rapidly changing conditions due to
heavy snow and gusty winds will create periods of dangerous travel
Thursday aftn. These squalls could become widespread, and after
coordination with the northeast WFOs, it is possible that with
future model cycles some enhanced messaging may be needed to
highlight the threat.

Behind this front, as well as behind a subsequent shortwave on
Friday, increased CAA will spread across the Great Lakes leading to
periods of lake effect snow (LES). The progressive flow will
support shortwave ridging between the two impulses, so the duration
of any LES with each shortwave/front should be somewhat limited.
However, 850mb temps falling to -15C to -20C Wednesday
night/Thursday, and then -10C to -15C late Friday, will create
steep lapse rates and deepening inversion depths to support bands
of heavy LES. The heaviest LES snowfall accumulations within the
LES bands are expected in the typical NW snow belts across the U.P.
of MI, the NW L.P. near Traverse City, and then along the
Chautauqua Ridge and into the Tug Hill Plateau. In these belts,
3-day snowfall of 6-12 inches is possible, highest across the U.P.

...Mid-South to the Mid-Atlantic... Day 3...

Uncertainty abounds D3 with respect to a strung-out shortwave
exiting the Central Plains and becoming embedded within the more
zonal flow to the east. Although this shortwave is expected to be
of modest amplitude and fast moving, the accompanying upper jet is
progged to be powerful at over 150kts across the Mid-Atlantic,
leading to surface low pressure development across the Southeast.
This low will then race E/NE, producing a swath of at least light
wintry precipitation from the Tennessee Valley to the Mid-Atlantic states.

There has been at least a modest northward shift/trend in the MSLP
fields from the various global ensembles the past few runs, and
while the ECMWF operational remains the most aggressive/north, that
solution cannot be ruled out. In fact, the trends in the 250mb jet
streak and from evaluation of the clusters (for which the primary
variance is the amplitude of the trough across the east) could
suggest a more subtle northward track of this low which would shift
more wintry precipitation into the area. It is still too early to
iron out these details, but at least a low-end risk for a few
inches of snow is possible as reflected by WPC probabilities which
reach 10-30% for 1+ inches of snow across the Central Appalachians
and into eastern VA/MD. This is notably lower than the recent NBM probabilities, and the trends continue to increase, so it is worth
watching the evolution of this event during the next few days.

South of the potential moderate snow, an axis of light freezing
rain is also possible where a p-type transition occurs. While the
location of the heaviest icing is also uncertain, current WPC
probabilities indicate a 10-30% chance for at least 0.1" of ice
across northern NC and into southern VA.

...Northern to Central Rockies... Days 2-3...

The next chance for heavy snowfall totals in the northern Rockies
will develop as a low amplitude shortwave slides off of the top of
the Pacific ridge into the region late Thursday into Friday,
coincident with the LFQ of an impressive upper jet streak swinging
across the Northern Pacific. This will result in favorable mid to
upper level forcing along with a notable influx of Pacific
moisture, sufficient for some heavy totals , especially above
around 5000 ft as snow levels rise coincident with this moisture
plume moving into the area. Heavy snowfall accumulations are likely
D2 from the WA Cascades through the terrain of NW WY near
Yellowstone NP as reflected by WPC probabilities that suggest a
high risk (>70%) for 4+ inches, with impacts to many of the area
passes becoming likely.

Probabilities become even more impressive D3 across the higher
terrain from Glacier NP through Yellowstone NP including portions
of the Sawtooth/Salmon River ranges, Absarokas, terrain of NW WY,
and into the Park Range of CO. Here, WPC probabilities D3 reach
above 70% for 8+ inches, and D3 snowfall could be impressive above
generally 6000 ft where locally 1-2 feet is possible.

Weiss

$$
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FOUS11 KWBC 050815
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
315 AM EST Fri Dec 5 2025

Valid 12Z Fri Dec 05 2025 - 12Z Mon Dec 08 2025

...Great Lakes... Days 1-2...

Periodic mid/upper level impulses rotating within a broad cyclonic
flow pattern will continue to support rounds of light-to-moderate
lake effect snowfall across the upper Great Lakes through Saturday.
Friday features modest WAA over the Great Lakes via SWrly flow that
looks to produce periods of snow over the northwestern towns of
Michigan's Mitten, while a cold frontal passage on Saturday
revitalizes LES bands over the Michigan U.P. and downwind of Lake
Ontario over the Tug Hill. WPC probabilities show low-to-moderate
chances (30-60%) for snowfall totals >4" over northwest mainland
Michigan today. By Saturday, most snowfall totals over the eastern
Michigan U.P. and downwind of Lake Ontario is likely to range
between 1-4".

...Mid-Atlantic... Day 1...

The first winter hazards of the season for much of the Mid-
Atlantic is unfolding this morning. As weak low pressure slides
eastward over the Southeast, enhanced 290K isentropic ascent,
increasing 850-700mb WAA aloft, and strengthening low-level frontogenesis
is producing periods of snow from the central Appalachians and
Blue Ridge of WV/VA on east across the central/southern VA Piedmont
and across the DelMarVa Peninsula. Light snow is advancing as far
north as the Washington D.C./Baltimore metro areas, which is
may result in slick roads for the Friday AM commute. This will be
the first accumulating snow of the season, likely resulting in
hazardous travel conditions on untreated surfaces across much of
the Mid-Atlantic. Farther south, an icy overrunning setup looks to
unfold from the southern Appalachians on east across northern NC.
A wintry mix is likely to cause some minor ice accumulations on
roads, sidewalks, and vegetation Friday morning and could cause
travel delays. Snow should taper off by mid-afternoon with
lingering icy conditions across affected areas of the Mid-Atlantic
through Friday night.

Snowfall accumulations are likely to range between 1-4" from
southern WV and southwest VA across southern VA (including the
Richmond metro area) and into the lower DelMarVa Peninsula.
Localized totals >4" are possible in the Blue Ridge Mountains of
southwest VA. In terms of ice accumulations, most areas from the
VA/NC Blue Ridge on east across southern VA and northern NC can
expect minor accumulations less than a tenth of an inch, although
some of the southern Appalachians of NC could see localized amounts
approach one-tenth. The WSSI does depict Minor Impacts through
Friday afternoon for most areas referenced in this discussion with
some localized Moderate Impacts in the southern VA Piedmont.

...Pacific Northwest, Northern & Central Rockies... Days 1-3...

A highly active storm track into the Northwest will usher in
copious amounts of Pacific moisture from the Pacific Northwest on
east into the Northern and Central Rockies. A steady barrage of

90th climatological percentile PWATs will stream across the

Pacific Northwest into the Great Basin and Rockies today, with
another round of >90th percentile PWATs arriving in the Pacific
Northwest on Sunday. Synoptic-scale forcing will be located over
the Northern Rockies today, then over the Central Rockies Friday
night into Saturday as a persistent NW-SE oriented 250mb jet
streak places its diffluent left exit region overhead. Snow levels
over the Pacific Northwest will dip as low as 3,000ft while the
Northern Rockies generally hover around 4,000ft. As height falls
transpire today over the Northwest and continue through Saturday,
snow levels will drop to as low as 2,000ft, although the heaviest
snowfall will be confined to elevations above 5,000ft in the
Bitterroots, Lewis Range, and Sawtooth, above 6,000ft in the
Tetons, Absaroka, Big Horns, Bear River, and Wasatch Ranges, and
above 7,000ft in the central WY/CO Rockies. Snow looks to taper off
across the Central Rockies by Saturday evening, but the next
atmospheric river will deliver another plume of Pacific moisture
across the Pacific Northwest and northern Rockies on Sunday.

WPC probabilities are impressive Day 1 and 2 across the higher
terrain from Glacier NP through Yellowstone NP including portions
of the Sawtooth/Salmon River ranges, Absarokas, terrain of NW WY,
northern Utah, and into the Park Range of CO. Here, WPC
probabilities Day 1 and 2 reach above 70% for 8+ inches, and Day 1
and Day 2 snowfall could be impressive above generally 6000 ft
where locally 1-2 feet is possible. Over the next few days, WPC
probabilities paint a wintry picture across many of the Northern
and Central Rockies, as well as the higher elevations of the
Cascades (above 5,000ft) with high chances (>70%) for additional snowfall totals >18" in all of these listed ranges and elevations through
Saturday. In fact, the higher elevations of the Lewis Range,
Bitterroots, and Tetons have moderate-to-high chances (50-80%) for
snowfall totals >24". Moderate to heavy snow continues into Day 3
over the WA Cascades and northern Rockies, though probabilities
suggest less snowfall compared to the more snowy stretches on
Friday and Saturday. The WSSI shows many areas of Minor and
Moderate Impacts across the Northern and Central Rockies,
including some locally Major Impacts. The Major Impact potential
areas (considerable disruptions; dangerous travel and widespread
closures) include areas along the Wasatch east of Salt Lake City
and the more remote areas of these Intermountain West ranges.
Residents in these mountain ranges should prepare for a multi-day
stretch of winter weather that results in difficult and treacherous
travel conditions.

...Northern Plains & Midwest... Days 2-3...

The active pattern of Pacific moisture and disturbances traversing
the Northwest will result in at least one of these disturbances
reaching the Midwest late Friday night into Saturday. A slug of
rich Pacific moisture within the 700-300mb layer will advance
across the northern Great Plains and reach the Missouri River
Valley by Saturday. The synoptic-scale setup favors the development
of an 850mb low with sufficient 850-700mb FGEN and WAA to the north
and east of the 850mb low track to support a band of moderate-to-
heavy snow. The band of snow starts out Saturday morning across
the Dakotas, then heads for southern MN and northern IA by late
Saturday afternoon and evening, and begins to weaken in intensity
by early Sunday morning the snow reaches the Lower Great Lakes and OH Valley.

The latest WPC probabilities have increased with this forecast,
now supporting probabilities of 50-70% for snowfall totals >4" for
locations that banding (mentioned above) is most likely across the
Midwest. However, given the favorable synoptic and mesoscale
processes at play, a band of >6" snowfall totals that cause travel
headaches for residents in the Midwest is very much on the table,
as evident in the low-to-moderate chances (20-50%) for snowfall
totals >6" over northern IA. Those in the Midwest should continue
to monitor the forecast closely as additional changes in the
placement and totals of the heaviest snowfall could still change
over the next 24 hours.

...Northeast... Day 3...

There remains a good deal of uncertainty in the forecast
on Sunday with the GFS remaining aggressive in a more
amplified/phase solution compared to the ECMWF/CMC. The GFS is also
noticeably wetter than the GEFS over the Northeast. The ECMWF/CMC
camp shows a broader and less amplified 500mb trough over the Great
Lakes and southeast Canada, but enough 500mb PVA and lake-enhanced
snowfall bands are showing low chances (10-30%) for snowfall
totals >4" downwind of Lakes Erie and Ontario. Some minor impacts
to travel are possible as denoted by the WSSI-P showing low-to-
moderate chances (30-60%) for Minor Impacts on Sunday.

Mullinax
$$
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FOUS11 KWBC 060746
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
246 AM EST Sat Dec 6 2025

Valid 12Z Sat Dec 06 2025 - 12Z Tue Dec 09 2025

...Central Rockies.. Day 1...

500mb height falls, the divergent left-exit region of a strong
250mb jet streak, and a plume of anomalous PWATs (above the 90th
climatological percentile per ECMWF) are all working together to
produce heavy mountain snow from the Wasatch, Uinta, and Wind River
ranges to the Rockies of southern WY and much of CO. Upslope
enhancement will be focused along the Wasatch and CO/WY Rockies
through this morning. As the core of the best moisture content
exits east this afternoon, snow will gradually taper off Saturday
night. WPC probabilities sport high chances (>70%) for additional
snowfall totals >12" in the Wasatch above 8,000ft and CO/WY
Rockies above 9,000ft. WPC's WSSI highlights Moderate Impacts at
these listed elevations with some localized Major Impacts in the
more remote peaks of the UT, WY, and CO Rockies.

...Pacific Northwest & Northern Rockies... Days 1-3...

The Pacific Northwest and Northern Rockies will continue to contend
with the lingering effects of the ongoing atmospheric river (AR)
through the remainder of the day Saturday. WPC probabilities show
high chances (>70%) for additional snowfall totals >8" in the more
remote reaches of the WA Cascades, the Bitterroots, Lewis Range,
and as far south as the peaks of the Absaroka and Tetons. A brief
ridge of high pressure builds in Saturday night before the round
of Pacific moisture arrives Sunday morning. Temperatures will be a
little milder this time around, confining most snowfall to the more
remote reaches of the Cascades. Pacific moisture will spill over
into the Northern Rockies Sunday night as the next atmospheric
river arrives on Monday. The Monday AR will be more intense with a
plume of >99th climatological PWATs engulfing much of the Pacific
Northwest by Monday afternoon. While the moisture influx is more
extensive, the strength of the WAA will keep snowfall to the more
remote reaches of the Cascades. However, moisture that spills over
into the Bitterroots and Lewis Range will have enough cold air to
support locally heavy snowfall. Over this weekend and through
Monday, WPC probabilities show moderate-to-high chances (50-80%)
for snowfall totals >12" in the WA Cascades above 5,000ft and along
the Lewis Range, which does include Glacier NP. Expect any
mountain passes that remain open to contend with potential closures
this weekend and into early next week.

...Northern Plains & Midwest... Days 1-2...

Height falls ahead of an approaching 500mb vorticity maximum will
coincide with the divergent left-exit region of a 250mb jet streak
over the Northern Plains to support the development of low pressure
early this morning. A narrow band of 850mb WAA and FGEN over
eastern MT will pivot south and east towards southern ND and become
responsible for the initial band of snow this morning. As low
pressure deepens, a more organized 850mb low will form over
southern SD and central NE. A strengthening 850mb LLJ will direct a
surge of WAA in the 850-700mb layer ahead of the 850mb low.
Combined with a healthy 290K isentropic ascent amid SWrly flow, and
a moistening DGZ will ensue over southeast SD, northern IA, and
southern MN and periods of heavy snow will develop. WPC's Snowband
Probability Tracker depicts the potential for >1"/hr snowfall
rates over southeast SD beginning around midday and continuing over
northern IA through Saturday evening. After 00Z Sunday, the 850mb
low will weaken, taking on a positive tilt and becoming an open
wave. Light-to-moderate snow is expected through Saturday night
over northern IL and southern WI (including the Milwaukee and
Chicago metro areas), with light snow possible across the Great
Lakes on Sunday.

WPC probabilities show northern IA as having the best odds of
seeing the heaviest snowfall of the event with moderate chances
(40-60%) for snowfall totals >6". Probabilities suggest I-35
located north of Des Moines and south of I-90 have low chances
(10-20%) for localized amounts over 8". Elsewhere, the area
spanning Sioux Falls on south and east through southern MN and
eastern ND all sport >50% chances for >4" of snowfall. The WSSI
shows Minor Impacts from the Sioux Falls area of southeast SD to as
far east as the Milwaukee/Chicago metro areas due to the snowfall
Saturday night into Sunday morning. Across eastern MT and southwest
ND, WPC probabilities show low- to- moderate chances (30-50%) for
snowfall >2", but probabilities for >4" are generally <10%,
implying that most totals are likely to range between 1-4" through
Saturday afternoon.

It is worth noting bitterly cold temperatures will follow in wake
of this system Saturday night and through Sunday. By Sunday
morning, temperatures will be in the single digits across much of
the Midwest and lows below zero Sunday night. Any snow that falls
will likely stick around for a couple days, resulting in daily
recurrences of icy roads and the potential for black ice.

...Great Lakes & Northeast... Days 1-3...

A series of upper level disturbances tracking across the Great
Lakes and into the Northeast will cause both LES bands and some synoptically-focred snow across these regions this weekend and into
early next week. Some LES streamers off Lakes Superior, Erie, and
Ontario will keep accumulating snow in the forecast in the usual
snow belts of Michigan's U.P., the "Tip of the Mitt" in Michigan,
and across western NY. By Sunday morning the upper trough
responsible for the Midwest storm on Saturday will make its way
through these regions with light-to-moderate snowfall across
Michigan and much of the Northeast (minus the I-95 corridor
megalopolis). Most snowfall totals will range between 1-4",
although some of the LES belts may manage to see some snowfall
totals eclipse 4" on Sunday. It is possible an inverted trough axis
over the Gulf of Maine could produce locally heavy snow along the
coast of ME, but the trough is a progressive one and should limit
totals from being overly heavy (1-4" most likely). Lastly, while
high pressure builds in over the Northeast on Monday, an Alberta
Clipper makes its way toward the Upper great Lakes by Monday
evening with more light-to-moderate snow expected.

WPC probabilities over the next three days (Sat-Sun-Mon) show
moderate-to-high chances (50-80%) for snowfall totals >4" in the
typical LES belts of Michigan's U.P., northern Michigan, and
downwind of Lakes Erie and Ontario. When it comes to >8" of
snowfall, it is the eastern Michigan U.P. and northwest Michigan
where low-to-moderate chances (30-50%) are present. The WSSI shows
Minor Impact potential downwind of Lakes Erie and Ontario, which
does include the Buffalo metro area.

...Southern Appalachians... Days 2-3...

A quick moving 500mb trough will track from the TN Valley Sunday
night to the Southeast Coast by Monday afternoon. 500mb PVA ahead
of the upper trough will be paired with easterly low-level flow
that allows for some upslope enhancement along the southern
Appalachians. Snow will be at its heaviest Monday morning but taper
off by Monday evening. WPC probabilities show low-to-moderate
chances (30-50%) for snowfall totals >2" in portions of the VA/NC
Blue Ridge and Potomac Highlands of WV. Some localized totals could
top 4" in the VA/NC Blue Ridge.

Mullinax
$$
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FOUS11 KWBC 070816
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
316 AM EST Sun Dec 7 2025

Valid 12Z Sun Dec 07 2025 - 12Z Wed Dec 10 2025

...Pacific Northwest & Northern Rockies... Days 1-3...

The Pacific Northwest and Northern Rockies will face a steady
barrage of Pacific moisture over the next few days thanks to a
multi-day strong atmospheric river that is pinned between a strong
subtropical ridge off the coast of CA and a stalled, positively-
tilted upper low in the Gulf of AK. Today, PWATs start out around
the 90th climatological percentile throughout the Northwest, before
a more impressive plume of PWATs above the 99th climatological
percentile stream in on Monday. Even on Tuesday, as the subtropical
ridge expands a little farther north, a fire-hose of Pacific
moisture will continue into the Pacific Northwest that spills into
the Northern Rockies as well. Add in steady synoptically-forced
ascent aloft from a strong 250mb jet stream and persistent upslope
flow into many of these mountains ranges, and the recipe is for
heavy snowfall from the Olympics and Cascades to the western WY Rockies.

Today, snow levels largely look to start out around 3,000-4,000
ft, but rapidly rise across the Pacific Northwest above 5,000ft.
As the strong AR and its associated WAA aloft approaches on
Monday, these values increase to above 6,000 ft in the northern WA
Cascades and above 7,000 ft from Mt. Rainer and points south.
Farther east, snow levels will rise across the northern Rockies as
well, topping 6,000ft in many cases before falling on D3 as the AR
orients itself farther south as a shortwave trough ejects into the
northern Plains. Starting this morning and lasting through early
Wednesday morning, 72-hr WPC probabilities for more than 12 inches
are high (70-90%) across the WA Cascades above 5,000 ft, as well
as parts of the northern Rockies in ID, western MT, and western WY
above 6,000-7,000 ft. WPC probabilities even show speckled areas
of low-to-moderate chances (20-50%) for localized snowfall totals

30" in the more remote reaches of these regions through Tuesday night.

...Great Lakes & Northeast... Days 1-3...

This morning, the upper trough responsible for the Midwest storm
on Saturday will generate light-to-moderate snowfall across
Michigan and much of the Northeast (minus the I-95 corridor
megalopolis). Most snowfall totals will range between 1-4",
although some areas within the Tug Hill and Adirondacks may manage
to see localized snowfall totals eclipse 4" on Sunday. The upper-
level disturbance may produce a small area of low pressure off the
Maine coast that produces a fast moving band of snow over Downeast
Maine Sunday night. WPC probabilities do depict low chances
(10-30%) for snowfall totals >4" Monday night.

By Monday night, as high pressure builds in over the Northeast, an
Alberta Clipper makes its way toward the Upper Great Lakes Monday
evening with more light-to-moderate snow expected. Guidance is
coming into better agreement that strong SWrly flow ahead of the
Clipper will produce a band of heavy lake effect snow oriented from
Lake Michigan and far northwest Michigan aimed northward into the
eastern U.P.. WPC probabilities through Tuesday show moderate-to-high
chances (50-80%) for snowfall totals >4" in over the eastern
Michigan U.P. and northwest Michigan. The eastern Michigan U.P.
sports the highest chances for >8" of snowfall (30-50%). As the
Clipper's warm front moves east, sufficient 290K isentropic ascent
and 850-700mb WAA will give rise to snow over the eastern Great
Lakes and northern New England by Tuesday afternoon. Immediately
downwind of Lakes Erie and Ontario, snowfall totals will generally
range between 1-4". However, the Tug Hill has moderate chances
(40-60%) for snowfall totals >4" through early Wednesday morning.

...Southern Appalachians & Mid-Atlantic... Days 1-2...

A quick moving 500mb trough will track from the TN Valley Sunday
night to the Southeast Coast by Monday afternoon. 500mb PVA ahead
of the upper trough will be paired with easterly low-level flow
that allows for some upslope enhancement along the southern
Appalachians. Snow will be at its heaviest Monday morning but taper
off by Monday evening. This storm could have a surprise or two up
its sleeve as the 500mb vorticity maximum reaches NC Monday
afternoon, with some guidance showing some 850mb low development
off the coast of NC's Outer Banks. Should easterly low-level winds
increase, sufficient low-level WAA and moisture advection could
create a band of snow that results in a quick hitting 1-3" snow
event from as far north as the Richmond metro area on south along
I-95 and I-85 towards the Raleigh/Durham area. WPC probabilities
currently show low chances (10-30%) for snowfall totals >4" in
portions of the VA/NC Blue Ridge and Potomac Highlands of WV, but
it is possible those chances increase should the influences of the
500mb trough prove more substantial. This has the potential to
cause slick travel conditions for the Monday evening commute in
southern VA and northern NC.

...Northern Plains & Upper Midwest... Day 3...

By Tuesday morning, a vigorous 500mb shortwave trough with origins
from the large Gulf of AK longwave trough will race towards the
Northern Plains. Given its origins, this "Alberta Clipper" will be
more intense than most clippers. This is because it will have
exceptional synoptic-scale forcing aloft in the form of a roaring
150kt 250mb jet streak, plus anomalous moisture associated with the
strong AR over the Pacific Northwest. By 18Z Tuesday, the
clipper's MSLP looks to be sub-990mb, which ranks below the 1st
climatological percentile for this time of year. As the storm works
its way across the Dakotas Tuesday morning, impressive 290K
isentropic lift and corresponding 850-700mb FGEN will not only
help to sustain this potent clipper, but foster a potent band of
snow northeast of the 850mb low track. There is the potential for
an icy wintry mix just along and north of the surface warm front as
a protruding >0C warm nose forces snow to melt into the form of
sleet or freezing rain. But the storm's fast motion should limit
the impacts to around minor impacts (ice accretions less than a
tenth of an inch most likely).

By Tuesday night, the storm will remain in the mid-980s for
pressure as it races through WI and into MI by Wednesday morning.
WAA out ahead of the storm is likely to cause periods of snow to
envelope the eastern Great Lakes that include areas such as
northwest PA and western NY. From the Northern Plains the the Great
Lakes, not only will snow be problematic for traveling, but gusty
winds are likely to cause blowing and drifting across roads and
cause reduced visibilities. WPC probabilities show a swath of
moderate chance probabilities (40-60%) for snowfall totals >4" from
northeast ND on south and east through the Upper Midwest and the
northern half of Michigan's Mitten. Note there are also low-to-
moderate chance probabilities (20-50%) for totals >6", which does
show up on several deterministic guidance members.

While the storm's speedy forward motion should help to reduce the
chances for more prolific snowfall totals, hourly snowfall rates of

1"/hr combined with gusty winds will allow for Minor Impacts at

the very least. This is supported by the WSSI-P which depicts
moderate-to-high chances (50-70%) for Minor Impacts on Tuesday from
northern ND all the way to northern MI. Residents in the Upper
Midwest and Great Lakes should continue to monitor this storm
closely, as should residents in the Northeast as probabilistic
guidance shows measurable snowfall from this system is possible on Wednesday.

Mullinax

$$
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FOUS11 KWBC 080843
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
343 AM EST Mon Dec 8 2025

Valid 12Z Mon Dec 08 2025 - 12Z Thu Dec 11 2025

...Pacific Northwest & Northern Rockies... Days 1-3...

The Pacific Northwest and Northern Rockies will face a steady
barrage of Pacific moisture over the next few days thanks to a
multi-day strong atmospheric river that is pinned between a strong
subtropical ridge off the coast of CA and a stalled, positively-
tilted upper low in the Gulf of AK. Today, PWATs above the 99th
climatological percentile will engulf much of the Northwest. Even
on Tuesday and into Wednesday, as the subtropical ridge expands a
little farther north, a fire-hose of Pacific moisture will continue
into the Pacific Northwest that spills into the Northern Rockies
as well. Add in steady synoptically-forced ascent aloft from a
strong 250mb jet stream and persistent upslope flow into many of
these mountains ranges, and the recipe is for heavy snowfall from
the Olympics and Cascades to the western WY Rockies above the
wavering high snow levels.

As the strong AR and its associated WAA aloft approaches on
Monday, these values increase to above 6,500 ft in the northern WA
Cascades and above 7,000 ft from Mt. Rainer and points south.
Farther east, snow levels will rise across the northern Rockies as
well, topping 6,000ft in many cases before falling on Tuesday as
the AR orients itself farther south as a shortwave trough ejects
into the northern Plains. Then, snow levels once again rise on
Wednesday as levels increase above 6,000 ft from southern
Washington to west-central MT. Through Wednesday night, 72-hr WPC
probabilities for >18" are high (>70%) across the WA Cascades
above 5,000 ft, as well as parts of western MT, and western WY
above 6,000-7,000 ft. WPC probabilities even show speckled areas of low-to-moderate chances (20-50%) for localized snowfall totals

30" in the more remote reaches of these regions through Wednesday.

...Southern Appalachians & Mid-Atlantic... Days 1...

A 500mb trough tracking over the TN Valley this morning will race
east and off the Southeast Coast by this evening. 500mb PVA ahead
of the upper trough will be paired with easterly low-level flow
that allows for some upslope enhancement along the southern
Appalachians. Snow will be at its heaviest during the day on Monday
as Atlantic moisture is directed west to the north of a weak 850mb
low tracking across northern NC. This combined with sufficient
low-level WAA will generate a band of snow that results in a quick
hitting 1-4" snow event in southern VA and northern NC, to as far
north as the Richmond metro area and south along I-95 and I-85
towards the Raleigh/Durham area. WPC probabilities currently show
low chances (20-40%) for snowfall totals >4" in portions of the
VA/NC Blue Ridge, the Potomac Highlands of WV, and southern VA
south of the Richmond metro area. Localized snowfall totals of 5-6"
are quite possible, especially in the VA Blue Ridge. Probabilities
for >2" are 40-60% east of the Blue Ridge across southern VA and
is likely lead to slippery road conditions to start the workweek.
Latest WSSI does suggest Minor Impacts for most affected locations,
with a narrow Moderate Impacts (hazardous driving conditions) area
stretching from Roanoke, VA to the Richmond/Petersburg metro area
and as far east as Williamsburg, VA.

...Great Lakes & Northeast... Days 1-2...

Tonight, as high pressure builds in over the Northeast, the first
in a parade of "clipper" systems tracks over the Upper Great Lakes
with more light-to-moderate snow expected. Guidance continues to
highlight that strong SWrly flow ahead of the clipper will produce
a band of heavy lake effect snow oriented from Lake Michigan and
far northwest Michigan aimed northward into the eastern U.P.. WPC
probabilities through Tuesday show moderate-to- high chances
(50-80%) for snowfall totals >6" over the eastern Michigan U.P.. As
the clipper's warm front moves east, sufficient 290K isentropic
ascent and 850-700mb WAA will give rise to snow over the eastern
Great Lakes and northern New England by Tuesday afternoon.
Immediately downwind of Lakes Erie and Ontario, snowfall totals
will generally range between 1-4".

...Northern Plains, Midwest, Great Lakes, & Northeast... Days 2-3...

By Tuesday morning, a vigorous 500mb shortwave trough with origins
from the large Gulf of AK longwave trough will race towards the
Northern Plains. Given its origins, this "Alberta Clipper" will be
more intense than most clippers. This is because it will have
exceptional synoptic-scale forcing aloft in the form of a roaring
150kt 250mb jet streak, plus anomalous moisture associated with the
strong AR over the Pacific Northwest. By 18Z Tuesday, the
clipper's MSLP looks to be in the mid-upper 980mb range, which
ranks below the 1st climatological percentile for this time of
year. As the storm works its way across the Dakotas Tuesday
morning, impressive 290K isentropic lift and corresponding
850-700mb FGEN will not only help to sustain this potent clipper,
but foster a potent band of snow northeast of the 850mb low track.
There is the potential for an icy wintry mix just along and north
of the surface warm front as a protruding >0C warm nose forces snow
to melt into the form of sleet or freezing rain. But the storm's
fast motion should limit the impacts from freezing rain to around
minor impacts (ice accretions less than a tenth of an inch most likely).

By Tuesday night, the storm will remain in the mid-980s for
pressure as it races through WI and into MI by Wednesday morning.
WAA out ahead of the storm is likely to cause periods of snow to
envelope the eastern Great Lakes that include areas such as
northwest PA and western NY. From the Northern Plains the the Great
Lakes, not only will snow be problematic for traveling, but gusty
winds are likely to cause blowing and drifting across roads and
cause reduced visibilities. Recent 00Z guidance suite has given
some credence to the EC-AIFS and GFSAI being more on the southern
track of guidance, but there are still a few members that remain a
little farther north. WPC probabilities show a swath of high-chance probabilities (>70%) for snowfall totals >4" from northeast ND on
south and east through the Upper Midwest and the northern half of
Michigan's Mitten. Note that probabilities have increased to
moderate-chance level (40-60%) for totals >6", which is increasing
confidence in a travel-disrupting winter storm on Tuesday.

While the storm's speedy forward motion should help to cap the
chances for more substantial snowfall totals, hourly snowfall rates
of >1"/hr combined with gusty winds will allow for minor to
moderate impacts, some of which will occur during the Monday
evening commute. This is supported by the WSSI-P which depicts high
chances (>70%) for Minor Impacts on Tuesday from northern ND all
the way to northern MI. Residents in the Upper Midwest and Great
Lakes should continue to monitor this storm closely, as should
residents in the Northeast as probabilistic guidance shows
measurable snowfall from this system is possible on Wednesday.

By Wednesday morning, the storm will race into Ontario with strong
850-700mb WAA overrunning a very cold air-mass in the Northeast.
Look for periods of snow to occur from the Central Appalachians on
north through the northern Appalachians. WPC probabilities show moderate-to-high chances (50-70%) for >6" in the Adirondacks, Tug
Hill, the Green and White Mountains. Some valleys in northern New
England have moderate chances (40-60%) for >2" of snowfall before
any issues with mixing or changing to rain occur. As the storm
tracks through the St. Lawrence River Valley, cyclonic flow of the
Great Lakes will spark additional LES bands over the typical snow
belts, including some upslope ascent into the central Appalachians
through early Wednesday morning.

Mullinax/Snell
$$
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FOUS11 KWBC 090828
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
328 AM EST Tue Dec 9 2025

Valid 12Z Tue Dec 09 2025 - 12Z Fri Dec 12 2025

...Pacific Northwest through the Northern High Plains.. Days 1-3...

Prolonged moisture spilling east from a strong atmospheric river
(AR) with multiple embedded waves will spread heavy snow into the
Intermountain West through late-week.

The strong AR will surge onshore the Pacific Northwest this
evening as a shortwave lifts into British Columbia with
impressively confluent and zonal flow pushing into WA/OR. IVT
probabilities for 750 kg/m/s exceed 90% during this time near the
WA/OR border, aided by a powerful Pacific jet streak of over 150
kts moving into British Columbia. This will be the beginning of a
long duration and impressive plume of IVT surging from the Pacific
Northwest and then spilling across the terrain and diving into the
High Plains through late week. While there will be multiple surges
of elevated IVT (and so not a continuous period of heavy
precipitation), in general the entire forecast period will be
unsettled, and IVT exceeding the CFSR climatology is progged via
NAEFS for multiple periods Wednesday and Thursday - indicating the
impressive available moisture associated with this system.

As with most ARs, the forcing and moisture will be attributed to
potent WAA, and this will drive snow levels to well above normal
levels for early December, likely reaching 8000-9000 ft in many
areas west of the Continental Divide and south of a wavering
stationary front/baroclinic boundary that will not only be a
demarcation for colder temperatures, but also provide a surface for
a subtle increase in isentropic ascent and fgen across the region.
Since snow levels south of this front will be so high, any heavy
snow should be confined to only the higher peaks of the northern WA
Cascades, far Northern Rockies, and into NW WY D1-D2 where WPC
probabilities are continuously high (above 70%) for 6+ inches both
days, especially in the northern WA Cascades and higher elevations
surrounding Yellowstone NP.

Then during D3, more significant snowfall becomes probable east of
the Northern Rockies in response to Arctic high pressure sinking
south out of Saskatchewan, driving a cold front to bank into the
terrain from the NE. This will sharpen the baroclinic gradient,
intensifying the resultant fgen, and increase isentropic ascent as
IVT continues to surge eastward beneath the potent Pacific jet
streak arcing to the southeast from British Columbia. With latest
WSO and WSSI-P guidance now showing >50% probabilities for snowfall
totals surpassing warning criteria and Moderate Impacts, confidence
is increasing in an axis of heavy snow spread NW to SE beneath
this jet streak and just north of the front across MT through D3, and
into the western Dakotas by D4. Current WPC probabilities for more
than 8 inches of snow are as high as 70% in the Northern Rockies
near Glacier NP above 7000 ft, with a larger footprint of
moderate-to-high chances (50-80%) across the heart of Big Sky
Country that includes mountain ranges such as the Little Belt, Big
Snowy, and Absaroka.

...Northern Plains through the Great Lakes and Northeast... Days 1-3...

Two distinct fast-moving shortwaves will race across the region
through late-week bringing several rounds of wintry precipitation.

The first of these will stem from a potent vorticity maxima and
associated shortwave trough which will dig out of Manitoba this
evening, reaching Michigan this morning, and then crossing New
England to exit into Canada by Wednesday morning. This feature will
remain of modest amplitude and the corresponding downstream jet
streak does not appear well positioned for any enhanced deep layer
ascent to cause cyclogenesis. Despite this, some increased
isentropic ascent from 280K-290K will cause a swath of moderate to
heavy snowfall tonight through Tuesday, with the speed of the
system the primary limiting factor to snowfall. Favorable ascent
into the DGZ will likely yield briefly heavy snow rates, especially
in MN/WI/MI before weakening into New England, with moderate snow
accumulations expected. WPC probabilities for even 2" of snow are
quite limited for this event, but periods of moderate to briefly
heavy snow could create hazardous travel for the monday commutes
for parts of WI, MI, and into Upstate NY.

Immediately in the wake of this first system a second, and likely
more amplified, shortwave and accompanying vorticity lobe, will
swing southeast out of Alberta/Saskatchewan and dive into the
Northern Plains by this afternoon. This shortwave is progged to
deepen during its progression, and while it should maintain a
positive tilt through its lifetime, it will gain amplitude and dive
farther south than the initial impulse. The resulting impressive
height falls will overlap efficiently with the LFQ of an impressive
Pacific jet streak following in its wake, producing intense deep
layer lift which will help deepen a surface low /Alberta Clipper/.
There is continued spread among the various deterministic models
(generally a global vs. high-res dichotomy) and their accompanying
ensemble spreads, but in general the differences are small leading
to high confidence in a track from ND Tuesday aftn to lower
Michigan Wednesday morning to northern Maine/Quebec Thursday morning.

In addition to the robust synoptic lift, ascent will become
enhanced through a progressive overlap of 285K-295K moist
isentropic ascent (mixing ratios as high as 4g/kg) with 850-600mb
fgen. This will be well aligned to the most impressive left-exit
diffluence, and directed into the primary snow growth region /DGZ/,
suggesting some banded snow with heavier snow rates occurring N/E
of the low- level circulation. This is reflected by the WPC
prototype snowband tool suggesting at least 1"/hr snowfall rates
diving across the region. While the temporal duration of these snow
rates, owing to the speed of the system, should cap the snowfall
amounts, some secondary banding is possible on the NW side of the
low in response to intensifying deformation, especially Tuesday
night into Wednesday. This may lead to some locally higher snowfall
totals, but at this time, WPC probabilities D1 for 4+ inches of
snowfall reach 50-70% from far eastern ND through much of northern
MN (south of the Arrowhead, however), with a more pronounced stripe
of 50+% probabilities for more than 4 inches on D2 across this same
area and extending into WI and lower MI. The transient nature of
the system will limit the high-end snowfall, but some areas locally may
receive around 8 inches of snowfall.

Additionally, south of this axis of heaviest snow, a transition
zone of mixed precipitation, including freezing rain is expected,
leading to at least modest ice accretion. While light freezing rain
is expected from far eastern MT through lower MI, the greatest
chance (10-30%) for more than 0.1" of icing exists across eastern
ND and western MN.

As this storm exits the Great Lakes and moves into Ontario D3, the
downstream strong WAA will overrun a very cold antecedent airmass.
This will create a broadening plume of wintry precipitation,
falling primarily as snow from Upstate NY through northern New
England, with some mixing, including periods of freezing rain,
expected farther south into the northern Mid-Atlantic and southern
New England. Total accumulations of wintry precipitation should be
less than areas upstream, but WPC probabilities early D2 into D3
for 4+ inches of snow reach 50-90% for portions of western PA and
across the southern Adirondacks, Greens, Whites, and terrain of northern ME.

Finally, behind this system a brief period of favorable NW flow
will create lake effect snow (LES) and upslope snow across the
eastern Great Lakes and into the Central Appalachians. While some
of this snow will fall on top of the synoptic snow noted above
(and is included in the snowfall probabilities), and additional 4+
inches of snow has a moderate risk of occurring across the Chautauqua
Ridge from D2 into D3. Similar probabilities for 4+ inches of snow exist
in the higher terrain of WV as well where upslope flow and gusty winds
could create hazardous impacts. The Tug Hill Plateau, in
particular, has rather high chances (>70%) for snowfall totals
surpassing 8" with even low-to-moderate chances (30-50%) for
snowfall topping 12 inches.

Weiss/Mullinax
$$
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FOUS11 KWBC 100825
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
325 AM EST Wed Dec 10 2025

Valid 12Z Wed Dec 10 2025 - 12Z Sat Dec 13 2025

...Pacific Northwest through the Northern High Plains... Days 1-3...

The atmospheric river (AR) plaguing the Pacific Northwest with
copious amounts of rainfall continues today and into Thursday with
anomalous Pacific moisture coupled with >90th climatological
percentile winds within the 700-200mb layer over WA, northern ID,
and much of MT. Snow levels will be on the rise today, reaching
anywhere from 7,000-9,000ft as the 500-200mb jet core drifts north.
This should begin to force most passes to changeover to rain,
while any lingering snow occurs in the more remote areas of the
Cascades and Lewis Range. The only notable area for heavy snowfall
today is along the >9,000ft peaks of the Absaroka, Tetons, Big
Horns, and Wind River ranges of southern MT and western/northern
WY. WPC probabilities show moderate-to-high chanceS (50-70%) for
snowfall totals >8" through Wednesday night.

Focus turns to Thursday as an Alberta Clipper tracking across
eastern MT helps to usher in an Arctic front from southern Canada.
As the Arctic high builds in from the north, low-level easterlies
will upslope into central and western MT at the same time a ribbon
of 700-300mb moisture streams in overhead. 700mb WAA within W-NW
flow will encounter the Arctic air-mass and result in a band of
700mb FGEN over central MT by Thursday night, resulting in a
quasi-stationary zone of heavy snow over the heart of Big Sky
Country. Heavy snow will linger over the heart of MT through Friday
afternoon before drifting east into eastern MT and the western
Dakotas Friday night. As the band advances east, downsloping winds
and a drying within the 800-500mb layer could cause precipitation
to change over to a wintry mix in central MT, potentially
resulting in a glaze of ice atop fresh snow Friday night.

WPC probabilities moderate-to-high chances (50-80%) for snowfall
totals >8" in central MT with even some low-chance probabilities
10-30%) for isolated totals surpassing 18". The Lewis Range above
5,000ft are likely to receive anywhere between 12-24" of snowfall,
with the remote reaches of the Big Snowy and Little Belt Mountains
potentially exceeding 24". The WSSI-P Moderate probabilities in
central MT are >50% in central and south-central MT, with
Interstates 90, 94, and 87 all at risk of seeing hazardous travel
conditions, with some potential for considerable disruptions and
closures as well. This is depicted in the WSSI-P as well,
indicating 10-20% chances for Major Impacts along portions of these
Interstates Friday and into Saturday morning.

...Great Lakes & Northeast... Days 1-3...

A shortwave trough responsible for the heavy snow across portions
of the Upper Midwest will strengthen as it tracks through the OH
Valley today. As it does, strong WAA out ahead of the trough will
work in tandem with the left-exit region of a 250-500mb mean
layered left-exit region over the Northeast to produce widespread
precipitation today from the central Appalachians to New England.
An exceptionally cold/dry antecedent air-mass by early December
standards will keep wet-bulb temperatures cold enough to support
snow at the onset across northern PA, the Catskills, Tug Hill,
Adirondacks, Berkshires, and the rest of the New England mountains
through Wednesday afternoon. Farther south, central and eastern
PA, as well as northwest NJ, are likely to see an icy wintry mix
this morning that could result in slick roads, particularly after
following a couple very chilly days where surfaces have been
steadily below freezing. From this "front-end thump" of WAA-driven
and some upslope enhanced snowfall, snowfall totals are likely to
range mostly between 1-4" with the higher totals confined to the
Tug Hill, Adirondacks, Berkshires, Green, and White Mountains where
WPC probabilities show high chances (>70%) for snowfall totals >6"
through Wednesday night.

As low pressure tracks into the St. Lawrence Valley tonight, CAA
within cyclonic flow on the backside of the storm will kick-start
the Lake Effect Snow (LES) machine, as well as supply the central
Appalachians with pronounced upslope snowfall. Precipitation will
fall as snow across the Central Appalachians with lowering snow
levels throughout the day Wednesday and impressive 40-50 kts winds
at 850mb will mix down to cause strong winds within increasing
snowfall rates. This will result in dangerous travel conditions in
the Central Appalachians with whiteout conditions expected above
2,000ft. Snow and winds should gradually taper off Thursday
morning. WPC probabilities show moderate-to-high chances (50-70%)
for snowfall totals >6" with localized low-chance probabilities
(10-30%) for amounts >12". Elsewhere, the LES belts over the
eastern Michigan U.P., northwest section of Michigan's Mitten,
along the Chautauqua Ride, and down wind of Lake Ontario will see
LES bands that stick around these areas through Thursday, with the
band off of Lake Ontario lingering into Friday as well. Through
Friday morning, the Tug Hill Plateau sports high chances (>70%) for
snowfall totals topping 12", with moderate-to-high chances (40-70%)
for >12" amounts along the Chautauqua Ridge through Friday morning.

...Northern Plains, Midwest, Lower Ohio Valley, & Central
Appalachians... Days 2-3...

A potent clipper emerging from eastern MT Thursday morning will
race southeast into the heart of the Midwest by Thursday evening.
Healthy 850mb WAA and FGEN to the north and east of the low track
will cause a narrow band of snow light-to-moderate snow from the
eastern Dakotas and southern MN to the nose of IA, and in some
cases a wintry mix across the northern High Plains. The 850mb
FGEN/WAA pivots over the Lower Ohio Valley Thursday night and
reaches the Central Appalachians by early Friday morning. WPC
probabilities show generally lw-to-moderate chances (20-50%) for

4" of snow from central MN on south and east across northern IL,

south-central IN, and southern OH. The highest probabilistic
chances for >4" of snowfall resides in the Potomac Highlands and
central Appalachians of eastern WV and western MD. Here, WNWrly
upslope winds within a 290K isentropic regime and higher SLRs will
provide a favorable environment for locally heavy snowfall. WPC
probabilities show most of the Potomac Highland and central
Appalachians in eastern WV and western MD have moderate-to-high
chances (50-70%) for snowfall totals >4", with some guidance
indicating low chances (10-30%) for localized totals surpassing 10".

There are some members of guidance that depict a chance for light
snowfall across the Mid-Atlantic on Friday, particularly the Blue
Ridge of VA/WV and potentially in the northern VA/northern
MD/southern PA. ECMWF and GFS show weak 700mb Q-vector convergence
over the region with just enough 700-300mb layer saturation to
support a chance for light snow. WPC probabilities show low chances
(10-30%) for >1" snowfall totals across southern and central PA,
northern MD, and northwest VA. While referencing >1" snowfall
potential may seem trivial to mention, recent Mid-Atlantic
snowfall events over the past week has seen snowier trends inside
of 60 hours. It is worth monitoring, but overall snowfall and
travel disruption potential at this time would be light. The WSSI-P
does show 10-20% odds for Minor Impacts across portions of northern
VA and northern MD on Friday.

Mullinax
$$
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FOUS11 KWBC 110840
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
340 AM EST Thu Dec 11 2025

Valid 12Z Thu Dec 11 2025 - 12Z Sun Dec 14 2025

...Montana... Days 1-2...

A swath of heavy snowfall is likely tonight into Friday across
much of central and eastern MT. A strong cold front will drop
south today in response to a building mid level ridge off the West
Coast. While considerably weaker than prior days, IVT is still
forecast over the 97th percentile over MT, with PWs around the 90th
percentile. This moisture will override the cold front and result
in a swath of significant snowfall. The latest WPC probabilities
indicate a high chance (greater than 80%) of >4" of snow over much
of central and eastern MT, with portions of the area likely to
exceed 8". This is expected to be more of a prolonged moderate
snowfall with the event picking up in intensity later tonight and
ending late Friday night...although periods of more intense
snowfall rates are likely.

...Great Lakes into Northeast... Days 1-3...

Cold advection within cyclonic flow around the storm system
exiting the Northeast will result in several lake effect snow bands
today. The most prominent bands will be over the Chautauqua Ridge
and off of Lake Ontario towards Syracuse. WPC probabilities give
both of these areas a greater than 70% chance of an additional 4"+
of snow today into tonight.

On Friday a weak area of low pressure will bring an initial batch
of light WAA snow to the Great lakes, followed by CAA lake effect
snow in its wake. WPC probabilities of exceeding 6" of snow with
this event are over 50% across the lakeshore of the U.P. of
Michigan, northwest lower MI, and the favored areas downwind of
Lake Erie and Ontario. While some areas may locally exceed 8", this
is not expected to be a high end lake effect event given the
relatively short duration of the most favorable ingredients.

...Dakotas, Midwest, Ohio Valley, & Central Appalachians... Days 1-2...

Northwest flow will support a clipper system moving from the
Northern PLains into the OH Valley today into Friday morning
resulting in a swath of light to moderate snowfall amounts.
Initially we should see a swath of freezing rain this morning from
portions of south central ND into central SD just north of the
shallow cold front, with the latest WPC forecast supporting some
ice accumulations of around or even a bit higher than 0.10".
However as the system quickly moves east today the main
precipitation type will be snow, with perhaps just a bit of a mix
and/or rain on the far southern extent of the precipitation shield.

Even at this short lead time there remains some uncertainty with
the exact axis of highest snowfall with this system. The 00z high
res models remain north of the global guidance, but they did trend
south compared to their 12z runs. The latest WPC preference takes
a consensus approach, resulting in a swath a bit south of the 00z
HREF mean, and a tad north of the global model consensus. The quick
movement of this system will limit snowfall magnitudes, although
the latest WPC probabilities depict a swath of a 30-50% chance of

4" of snow from portions of central IL into south central IN and

towards the KY border. These probabilities could be a bit low, with
these quick hitting clipper systems often verifying with a narrow
band of higher amounts, and a good amount of this snow falling
overnight helping with accumulations. Thus would expect to see a
swath of 4-5" with this system, with a few totals over 5" possible.

The system will begin to weaken as it moves into the Mid-Atlantic,
and thus not expecting much in the way of snow to make it east of
the Appalachians. Even with the weakening nature of the system,
upslope flow will still support accumulating snow over the favored
terrain of WV into southwest VA, with >4" snow probabilities
peaking in the 30-50% range over southeast WV Friday.

...Corn Belt, Midwest, Ohio Valley and Mid-Atlantic... Day 3...

Another quick moving system will eject into the Northern Plains
Friday night into Saturday, quickly moving across the OH Valley on
Saturday and into the Mid-Atlantic Saturday night into Sunday
morning. This will be a quick moving system which will limit
snowfall magnitudes, however widespread minor impacts can be
expected, with WPC probabilities already indicating a 60-80%
chance of >2" of snow from SD into OH. The probabilities of >4"
drop into the 10-40% range...indicating that totals of this
magnitude are currently unlikely to be widespread, but may very
well occur in localized swaths along the track.

As this system approaches the Appalachians the mid level trough
begins to dig and take on more of a neutral tilt. This will
increase mid and upper level southerly flow and begin the process
of coastal low development. Most likely this trough will remain
too progressive and take on a negative tilt too late to bring a
significant snowfall risk to the Mi-Atanltic and Northeast.
However, it is becoming increasingly likely that we see enough
increase in forcing to see an expansion of some accumulating snow
into the Mid-Atlantic Saturday night.

This expected evolution will support a more prolonged period of
accumulating snowfall into portions of WV and southwest PA, where
probabilities of >4" of snow have increased into the 50-80% range,
with >6" probabilities even over 40%. By later Saturday night model
guidance is trending towards a more favorable solution for a quick
shot of snow even into coastal areas of the Mid-Atlantic. In fact
the 00z deterministic GFS/CMC/ECMWF/AIFS would all bring some
accumulation of snow into the DC to NYC corridor. From an ensemble
perspective, the WSSI-P shows a 50-60% chance of minor impacts
from DC to NYC and a 10-20% chance of Moderate impacts. This
generally seems like a 1-3" event, but the latest guidance does
support the potential for a narrow axis of 3-5" somewhere over the
eastern Mid-Atlantic. This is a lower probability outcome and
likely the ceiling for this event given the quick storm motion, but
the risk is supported by the aforementioned low WSSI-P moderate
probabilities and some low >4"+ WPC probabilities. These quick
northwest flow systems are tricky to pin down with much lead time,
so future adjustments to the forecast are likely.

Chenard
$$
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FOUS11 KWBC 120908
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
408 AM EST Fri Dec 12 2025

Valid 12Z Fri Dec 12 2025 - 12Z Mon Dec 15 2025

...Montana... Day 1...

NWly jet downstream of an amplifying ridge axis off the PacNW coast
continues to intensify through this morning with 250mb winds
increasing above 150kt over south-central Alberta. Pacific moisture
continues to shift inland south of this jet which meets
particularly cold air from the Canadian Prairies that is banking
up against the eastern slopes of the MT Rockies. The amplifying
ridge maintains the jet dynamics with banding over central MT now
expected to drift north to northern MT through this evening before
ejecting southeast over the north-central Plains late
tonight/Saturday morning.

Ongoing freezing rain along the southern periphery of the banding
in valleys in the eastern slopes will continue this morning with
only a narrow strip of wintry mix shifting north with the southern
extension rest of today. Otherwise this is fluffy with consistent
0.5"/hr rates across the MT Plains through this evening (per 00Z
HREF) with SLR in the 15 to 18:1 range. Day 1 PWPF for >6" snow is
over 40% across much of north-central to eastern MT, including
around Havre where probabilities are above 70%.

...Northern Plains through the Midwest to the central Appalachians...
Days 1-2...

A reinforcing trough over the Gulf of Alaska early this morning
rides an increasing NWly jet today, reaching southern Saskatchewan
tonight. This trough is the catalyst for allowing ongoing snow
banding over MT to eject southeast across the Dakotas late tonight
and the Midwest Saturday. Strong jet dynamics and ample cold air
with Arctic origin allows for decent snow rates through this swath, consistently over 0.5"/hr per the 00Z HREF. Day 1.5 PWPF for >4"
are lower over South Dakota where the bands are fairly progressive,
generally 30%, but higher over Iowa through north-central IL and
central IN where the band pivots east with values of 40-60%.
Probabilities continue to ramp up to the east over Ohio later
Saturday before orographic lift brings increasing probabilities
for >6" to northern WV, peaking for areas just west of the
Allegheny Front where Day 2 PWPF for >6" are 40-70%.

This swath is forecast to be a bit north of the current snow
tracking east from southern IN and eastern KY. These two
clippers will produce decent swaths of snow and combine to cover
large areas of the Midwest with snow through Saturday.

...Mid-Atlantic through the coastal Northeast... Days 2-3...

The Saturday shortwave trough/clipper amplifies an upper low over
Lake Superior Saturday allowing it to further develop and dig
south over the eastern Great Lakes Saturday night. The surface
component of this low develops as a trough off the Mid-Atlantic
coast to the Outer Banks by 12Z Sunday. Right entrance jet dynamics
and this developing surface trough allow moderate to locally heavy
banding to develop over the central/northern Mid-Atlantic through
southern New England Saturday night into Sunday. Placement of
banding with a key area of 0.25" QPF remains a bit uncertain at
this time, but areas from Baltimore through New Jersey and
possible Long Island are of most concern now. Day 2.5 PWPF for >4"
are 30-40% around Philly and around 20% over southern Connecticut
through southeast Mass. Confidence has increased on the snow
advancing and reaching the NYC metro late Saturday evening.

Rapid low pressure development is expected off the Northeast coast
Sunday which will maintain offshore flow and should allow ocean/bay
enhanced snow for the Cape and Islands through Sunday night. Day 3
PWPF for >4" are around 30% for Cape Cod.

...Great Lakes... Days 1-3...

Persistent troughing across the east will maintain cold conditions
as a storm brings another round of lake enhanced and effect snow
across the Great Lakes tonight through Sunday. Low pressure
currently over Manitoba dives southeast to Lake Superior tonight
before amplifying by an aforementioned shortwave trough. Westerly
flow ahead of this low brings synoptic snow with lake enhancements
for the U.P. and tip of the L.P. mitt where Day 1.5 PWPF for >6" are 30-50%.

This westerly flow then crosses the eastern Great Lakes early
Saturday bringing renewed cold air advection and transient single-
banding to snow belts east of Cleveland through the Chautauqua
Ridge and across the Tug Hill where Day 2 PWPF for >6" are 40-70%.
LES then continues on NWly flow behind the low on Sunday with Day 3
PWPF for >4" 40-80% in northwest PA and around Syracuse.

Jackson

...Extreme Cold Key Messages are in effect and linked below...

https://www.wpc.ncep.noaa.gov/key_messages/LatestKeyMessage_1.png

$$
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FOUS11 KWBC 130906
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
406 AM EST Sat Dec 13 2025

Valid 12Z Sat Dec 13 2025 - 12Z Tue Dec 16 2025

...North-Central Plains, Midwest to the Central Appalachians... Day 1...

Low to mid-level low is over north shore of Lake Superior with a
reinforcing shortwave trough over far northeast MT. This wave is
riding a powerful 140kt jet that extends across the Midwest and
through the Mid- Atlantic. Intensifying fgen (both through WAA and
the result of the upper jet streak position) will be sufficient to
drive omega through the snow growth zone through this evening.
With strong lift occurring into a DGZ that is deepening in the cold
airmass, periods of heavy snow are expected, especially within a
narrow translating band from Iowa through Ohio and northern WV
today. Forcing is strong enough to warrant a risk for thundersnow
particularly midday/early afternoon over central IL/IN where 1"/hr
rates are possible per the 00Z HREF.
The bands rise over the Allegheny Plateau this evening where
orography once again brings a risk for 1"/hr rates. Day 1 PWPF for

6" are around 10% in central IL/IN and quickly increase from 40%

to 70% across far southeast OH through north-central WV. Snow rates
drop off Sunday morning over the central Appalachians, but the
upper trough does cross midday, so continued upslope snow showers
can be expected at least through the day light hours.

...Mid-Atlantic through Southern New England... Days 1/2...

Upper low stalls over northern Lake Superior today before ejecting
southeast tonight with the aid of a reinforcing shortwave. The
resultant upper trough axis reaches the Northeastern Seaboard
Sunday evening with downstream surface trough then low development
off the Mid-Atlantic coast Sunday morning. Right entrance dynamics
aid fgen banding to develop in the lee of the central Apps later
this evening, most likely over north-central MD east through NJ
before the surface trough/low offshore provides additional forcing
for more intense banding overnight to shift south and east. This
system is fairly progressive, but the frontal forcing in
increasingly cold air allows 0.75"/hr rates in the Mid-Atlantic,
extending to southern New England early Sunday. Marginal thermals
at the southern extend of the precip swath to begin with quickly
shift to all snow - this is aided the nighttime occurrence.

This event should last no more than 12 hours in any given location,
and the exact placement, timing, and intensity of the jet streak
and offshore trough will determine where the heavier bands setup
and pivot. Day 1.5 PWPF for >6" are over 10% from just north of DC
through Cape Co with a peak of around 30% for greater Philly.

...Great Lakes... Days 1-3...

Aforementioned low pressure system stalling over Lake Superior
today ejects southeast tonight with a reinforcing shortwave trough
passage on Monday. Subterranean DGZ under the low today makes for
coarse/low SLR snow, but some warming this evening brings back the
dendrites and 20:1 SLRs to the U.P.

Day 1 PWPF for >6" are 40-80% over NWly flow snow belts in the
eastern U.P. and east of Grand Traverse Bay. Wly flow snow belts
east of Lakes Erie/Ontario result in Day 1 PWPF >6" of 30-50% east
of Cleveland to the Chautauqua Ridge and over 80% for the Tug Hill
where single banding LES sets up this evening. Lull expected
for Sunday night as low level ridging shifts east of the Lakes. But
then shortwave crosses Monday with a decent, but transient swath of
lake enhanced snow. Light to locally moderate synoptically driven
snow across the Great Lakes region Monday with more single banding
in westerly flow over Lake Ontario into the Tug Hill where Day 3
PWPF for >6" is over 80%.

...Pacific Northwest... Days 2/3...

Potent atmospheric river arrives Monday morning to western WA/OR
with snow levels skyrocketing up to 9000ft over the Cascades. A
shortwave trough passage over WA late Monday brings snow levels on
the North Cascades down to 5000ft, reaching 4000ft on Tuesday.
Lower precip rates are expected behind the trough passage, but
moderate snow brings Day 3 PWPF for >6" in the 40-60% range in the
high northern WA Cascades.

The probability of significant icing is less than 10 percent.

Jackson

...Extreme Cold Key Messages are in effect and linked below...

https://www.wpc.ncep.noaa.gov/key_messages/LatestKeyMessage_1.png

$$
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FOUS11 KWBC 140851
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
351 AM EST Sun Dec 14 2025

Valid 12Z Sun Dec 14 2025 - 12Z Wed Dec 17 2025

...Mid-Atlantic through Southern New England... Day 1...

Positive tilt to the trough rounding the mid-level low centered
over Lake Huron this morning will continue to dig southeast as it
shifts across the Northeast through this evening. Surface low
development is underway along the Delmarva coast with rapid
strengthening today as it shifts northeast out to sea. Decent fgen
driven snow banding with rates around 1"/hr will continue to shift
south over the Mid-Atlantic as they begin to wrap around the sfc
low. These bands have reached the southeast Mass Cape and Islands
where they will pivot through the day and become ocean/bay enhanced
this evening as the low begins to pull away. This should result in
around 0.75" QPF which will be all snow with totals tempered a bit
from still warm waters. Day 1 PWPF for >4" after 12Z is generally
limited to Cape Cod and the Islands with probabilities of 40-70%.

Day 1 PWPF for an additional 2" after 12Z are generally 40-70% from
Rhode Island across Long Island, down the Jersey shore through
lower Delaware with 30% probs into the Northern Neck of VA and the
southern Delmarva.

Upslope snow rates west of the Allegheny Front dwindle through
sunrise with Day 1 PWPF for an additional 2" after 12Z are generally
30-70% for elevations in central WV above 2500ft.

...Great Lakes... Days 1-2...

Aforementioned low pressure system ejecting southeast from Lake
Huron today will activate Nly flow snow belts into the east-central
U.P. where Day 1 PWPF for >4" are 40-70%.

WNWly flow over the eastern Great Lakes this morning will veer
NNWly by this evening with pivoting bands from Erie and Ontario.
Day 1 PWPF for >4" are 30% inland from Erie, PA and 50-80% just
north of Syracuse.

Lull in LES expected tonight as low level ridging shifts east over
the Lakes. But a shortwave clipper approaches from the northwest
late tonight and crosses Monday with a decent, but transient swath
of lake enhanced snow over the northern Lakes before prompting
singl-band LES over the Eastern Great Lakes Monday night with the
DGZ centered on 850mb. Day 2 PWPF for >2" is 40-70% from the
Keweenaw Peninsula through the eastern U.P. and Tip of the Mitt
while there are 30% probs for >6" south of Buffalo and 60-80% for
the Tug Hill Plateau.

A return of ridging cuts off the eastern LES early Tuesday.

...Cascades and Northern Rockies... Days 2-3...

Potent atmospheric river arrives early Monday morning to western
WA/OR with snow levels skyrocketing up to 9000ft over the Cascades.
A shortwave trough passage over WA late Monday quickly brings snow
levels on the North Cascades back down to 5000ft by the evening,
reaching 4000ft overnight. Lower precip rates are expected behind
the trough passage, with Day 2 PWPF for >6" limited to the higher
WA Cascades. However, snow levels rise only a little Tuesday ahead
of the next wave that arrives Wednesday night. Precip rates
increase as snow levels remains around 4500 to 6000ft on the WA/OR
Cascades. Day 3 PWPF for >8" is over 80% across the higher WA
Cascades. Moisture surges inland TUesday night with snow levels of
5000 to 6000ft over the ID/MT ranges where Day 3 PWPF for >6" are 40-80%.

The probability of significant icing is less than 10 percent.

Jackson

...Extreme Cold Key Messages are in effect and linked below...

https://www.wpc.ncep.noaa.gov/key_messages/LatestKeyMessage_1.png

$$
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FOUS11 KWBC 150848
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
348 AM EST Mon Dec 15 2025

Valid 12Z Mon Dec 15 2025 - 12Z Thu Dec 18 2025

...Great Lakes... Day 1...

Some lake enhanced snow for Michigan this morning ahead of a
shortwave trough currently over the Arrowhead of MN. The greater
impacts are on the eastern Great Lakes where flow is already
backing westerly. Brief single-banding LES occurs this afternoon
off Lake Erie into the South Towns of Buffalo where Day 1 PWPF for

4" are around 60%. The greater LES formation is this evening with single-banding into the Tug Hill Plateau through the night before

tapering off Tuesday morning in notable warm air advection. The
saturated layer gets into the DGZ and the flow is fairly steady
state, so decent snows are forecast. Day 1 PWPF for >8" are around
80% for the Tug Hill.

...Cascades and Northern Rockies... Days 1-3...

A lead warm atmospheric river (AR) will bring mostly rain to the
PacNW through early afternoon with very high snow levels around
9000ft. A shortwave trough brings a cold front through by this
evening which will lower snow levels this evening amid lighter QPF
to around 4000ft in WA 5000ft in northern OR. Day 1 PWPF for >8"
are limited to the higher WA Cascades.

Snow levels rise back to 5000ft in WA and 6000ft in OR Tuesday as
the next moisture surge pushes inland. However, a sharper shortwave
trough axis pushes across the Cascades by 12Z Wednesday. This
potent cold front brings a sharp drop in snow levels after 06Z
Wednesday to around 2000ft in WA and 4000ft in OR. Again, the
precip rates rapidly drop with the snow levels, but there should be
impactful snow at pass levels including Snoqualmie. Day 2.5 PWPF
for >8" are over 80% for most of the WA Cascades. Low snow levels
and precip rates persist then through Wednesday night.

Moisture and windy conditions will progress eastward over the
Northern Rockies this afternoon and much more so Tuesday night.
Day 1.5 snow probs for >8" are 30-60% over the northwestern MT
ranges. Day 2.5 snow probs for >8" are 50-80% over the western MT,
central ID, and northwest WY ranges with rapid drops in snow levels.

The probability of significant icing is less than 10 percent.

Jackson

$$
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FOUS11 KWBC 160835
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
335 AM EST Tue Dec 16 2025

Valid 12Z Tue Dec 16 2025 - 12Z Fri Dec 19 2025

...Cascades and Northern Rockies... Days 1-3...

Snow levels on the WA Cascades rise from 4000ft to 5500ft through
this evening under brief ridging until a sharp shortwave trough
axis pushes across the Cascades by 12Z Wednesday on the head of a
170ft WNWly jet. This potent cold front brings a sharp drop in
snow levels tonight, reaching 2000ft in WA and 4000ft in OR early
Wednesday. The precip rates rapidly drop with the snow levels, but
there should be impactful snow at pass levels including
Snoqualmie. Low snow levels and moderate precip rates persist into
Thursday before an intense push of moisture and height rises move
in, particularly into Oregon. The latest WPC probabilities remain
high for snowfall accumulations >8" (particularly for the
Washington Cascades) each of days 1-3, with 72-hour probabilities
through Thursday remaining high for accumulations >24".

Moisture and windy conditions will progress eastward over the
Northern Rockies today, followed more surges tonight and Thursday,
with falling snow levels. The latest WPC probabilities for
snowfall >8" are moderate to high (40-80%) for the highest
elevations of central and northern ID and western MT Day 1,
expanding south through western Wyoming with 40-80% probs on Day
2, and then an increase over similar areas of MD/ID/WY on Day 3
with to 50-90%.

...Northern Plains, Upper Midwest, Great Lakes... Day 3...

Strong low pressure tracks eastward along the U.S./Canada border
roughly from Montana to Lake Superior Wednesday through Thursday. A
wintry mix is possible in the warm air advection ahead of the
system over the Upper Midwest Wednesday night, but the main concern
is the leading axis of heavy snow on the cold conveyor belt that
connects to a wrap around deformation band with an intense pressure
gradient and high wind/blizzard threat. Fairly fast forward motion
and the likelihood that most of the leading bands should be north
of the border limits the overall snowfall for the U.S. That said,
Day 2.5 WPC probabilities for snowfall >4" remain moderate
(40-70%) from northeast ND through far northern Minnesota, with
10-30% for >8" in the northern Arrowhead. In general, the wind
field should be worst south of the new snow, but over the Dakotas
and Minnesota which has a decent snowpack that could be driven into
ground blizzard conditions. Please stay tuned on this wind-whipped
forecast.

The probability of significant icing is less than 10 percent.

Jackson

$$
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FOUS11 KWBC 170805
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
305 AM EST Mon Nov 17 2025

Valid 12Z Mon Nov 17 2025 - 12Z Thu Nov 20 2025

...Northeast/Great Lakes... Day 1...

A deep closed low now centered over the Canadian Maritimes will
begin to lift north this morning and then accelerate later in the
day. Supported by deep northwesterly to west-northwesterly winds in
its wake, ongoing orographic and lake effect snow showers will
continue but gradually wane through the day. The northern
Adirondacks, Green, and White mountains will remain the focus for
upslope snows, with some potential for several more inches in some
spots, especially along the northern Greens, where WPC
probabilities for additional accumulations exceeding 4 inches
remain high.

Further to the west, there is a decent signal for a single band
intensifying off of Lake Ontario and shifting east across the
Finger Lakes, with WPC probabilities indicating several inches are
possible east-southeast of Syracuse.

Lastly, the band off of Lake Erie with a connection extending back
to Lake Superior is expected to wane and shift east, most likely
producing just another inch or two across parts of southwestern New
York and northwestern Pennsylvania today.

...California to the Central and Southern Rockies... Days 1-2...

An upper low will move across Colorado and Wyoming this morning.
Snow will continue to fall this morning across the western and
south-central Wyoming ranges, as well as the western Colorado
mountains, with additional accumulations remaining light for most
areas. Favorable upper jet-streak forcing along with moist
southwesterly flow may support some higher totals along the Sierra
Madre, Park Range, and Medicine Bow mountains in south-central
Wyoming and north-central Colorado. WPC probabilities indicate
additional totals over 4 inches are likely, especially for areas
above 8,000 ft.

A second low closing off within the base of a sharp trough
approaching northern California will continue to deepen and drop
south along the coast through today into early tomorrow. This
system is expected to linger as it settles along the southern
California coast tomorrow before rotating inland as yet another
Pacific system moves toward California late Wednesday into Thursday.

Areas of heavy snow are forecast to spread south along the Sierra
Nevada today, before diminishing tonight, but with light amounts
continuing across parts of the central and southern Sierra through
Tuesday. WPC probabilities indicate that two-day totals are likely
to exceed 8 inches for many locations in the central Sierra above
8,000 ft. Some locally heavy totals, exceeding 8 inches, are also
expected farther east in parts of the central and southern Nevada
ranges, and the southwestern Utah mountains.

...Central Plains/Upper Midwest... Days 1-2...

The previously noted low exiting the Rockies today is forecast to
move steadily east from the Central Plains into the mid and upper
Mississippi Valley tonight. Low to mid level frontogenesis along
with a coupled upper jet will support a stripe of moderate
precipitation developing from eastern South Dakota, through
southern Minnesota, into southern Wisconsin tonight. Dynamic
cooling will support rain changing to snow where this heavier band
sets up. While probabilities for accumulations beyond an inch or
two remain low, the potential for locally heavier amounts cannot be
ruled out.

Pereira

$$
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FOUS11 KWBC 180745
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
245 AM EST Tue Nov 18 2025

Valid 12Z Tue Nov 18 2025 - 12Z Fri Nov 21 2025

...Southern Minnesota into Central Wisconsin... Day 1...

Low to mid level frontogenesis and coupled upper jet forcing
accompanying an upper low moving moving through the central Plains
this morning is continuing to support a band of light to moderate
precipitation lifting north from Iowa and Illinois into southern
Minnesota and Wisconsin. General consensus of the models indicate
precipitation will remain mostly rain through the remainder of the
overnight with a changeover to sleet and snow near sunrise across
parts of southern Minnesota and central Wisconsin. WPC
probabilities indicate the greatest potential for accumulating snow
beyond an inch is across central Wisconsin, where snow is expected
to linger the longest before diminishing in the afternoon.

...California through the Southern Rockies... Days 1-3...

A series of upper lows impacting the West will continue through the
period, with the latest system now dropping south along the
California coast. This low is expected to settle into southern
California by late today and linger near the California-Mexico
border into early Thursday before the next system begins to kick it
east as it follows a path similar to its predecessor along the
California coast.

In addition to locally heavy snow along the southern Sierra Nevada
today, moist easterly flow along with favorable upper forcing is
expected to support heavy totals farther to the east along the
White Mountains as well. WPC probabilities indicate amounts greater
than 8 inches are likely for locations above 8,000 feet over the
next 24 hours. Amounts exceeding 8 inches are also expected for the
southern Nevada ranges north of Las Vegas and over the
southwestern Utah mountains.

Wednesday into early Thursday is expected to be a relatively
quieter period. High elevation snows will continue across the
Southwest into the southern Rockies, but apart from some isolated
heavier totals over southern Utah and the higher elevations of
northern and central Arizona, amounts are expected to be generally
light.

A broader threat for heavy snowfall will develop during the day on
Thursday, especially for the San Juan and Sangre de Cristo
mountains, as the leading low begins to move east. However,
southerly winds will keep snow levels high, with the higher
probabilities for accumulations greater than 6 inches remaining
mostly above 10,000 ft.

Meanwhile, mountain snow will spread south across
California on Thursday into Friday morning, but the progressive
nature of this next system will help limit the threat for
widespread heavy amounts.

Pereira

$$
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FOUS11 KWBC 190800
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
300 AM EST Wed Nov 19 2025

Valid 12Z Wed Nov 19 2025 - 12Z Sat Nov 22 2025

...California through the Southern Rockies... Days 1-3...

An upper low centered over Southern California this morning will
slowly translate eastward over the next 24 hours before the next in
a series of developing lows approaches the coast and begins to
eject it eastward. As the leading low moves east, it will continue
to direct deeper moisture and associated mid level energy farther
inland. With high snow levels in place at the onset, there will be
little threat for widespread heavy snow accumulations through early
Thursday. WPC's Day 1 probabilities shows the threat for
accumulations above 6 inches to be isolated and mostly confined to
the higher peaks of the southern Utah Mountains, the San Francisco
Peaks and White Mountains in Arizona, and the San Juans in
southwestern Colorado.

As the leading system moves east, the extent of light snow
accumulations is forecast to increase across the Colorado and
northern New Mexico ranges. However, accumulations greater than 6
inches will likely be limited to areas in the San Juans and Sangre
de Cristos above 10,000 ft.

Meanwhile, mountain snow will spread quickly south across
California from the southern Cascades to the northern Transverse
Ranges on Thursday. Given the progressive nature of this second
system and more modest moisture, widespread heavy snow
accumulations are unlikely. WPC probabilities for 24 hour amounts
exceeding 6 inches are limited mostly to the higher peaks of the
Sierra Nevada.

Similar to its predecessor, this second low is expected to settle
and linger over Southern California Friday into Saturday. The
footprint for heavy snow is expected to become even more
confined, limited to the higher peaks of the Transverse Ranges and
perhaps the southern Nevada mountains.

Pereira

$$
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FOUS11 KWBC 200815
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
315 AM EST Thu Nov 20 2025

Valid 12Z Thu Nov 20 2025 - 12Z Sun Nov 23 2025

...Southern & Central Rockies... Day 1...

An upper low over AZ this morning will take on an increasingly
negative tilt over northern Mexico though weaken overnight as it
mostly shears out to the east after 00Z. Snow will continue this
morning over northern AZ/NM into UT/CO with relatively high snow
levels >8000ft that will drop through the day. Some light snow will
still persist into D2 (early Friday) as lingering convergence and
upslope squeeze out another inch or two over the CO Rockies. WPC
probabilities for at least four inches of snow after 12Z Thu are
highest (>50%) over the highest peaks of the San Juans and the
Sangre de Cristos (generally above 10,000ft).

...California... Days 1-2...

A Pacific upper low will form early this morning just west of
WA/OR and dive south-southeastward today through NorCal then to a
position west of Los Angeles early Friday. With regions of
vorticity rotating around the main center, bouts of snow will move
through the CA terrain from the Trinity/Siskiyou mountains today
then through the Sierra later this afternoon into Friday. Snow
levels will be around 5000-6000ft this morning over NorCal and
around 6000ft over the central/southern Sierra this evening and
slowly drop overnight. Over SoCal, snow levels will be around
6500ft this afternoon and drop to around 6000ft overnight. The
upper low will be in no hurry to exit the region, moving through
northern Baja California Saturday evening. By then, most of the
precipitation will be confined to the lower elevations and mostly
rain (though snow may linger over the SoCal mountains).

WPC probabilities for at least six inches of snow are >50% above
about 9000ft over the Sierra. Across the San Gabriel and San
Bernadino mountains, with a longer duration of precipitation
through Friday, significant snowfall is quite probable. WPC
probabilities for at least eight inches of snow are >50% above
about 7000ft (around the elevation of Big Bear Lake). Three-day
totals may exceed 12-18" above 9000ft. This could cause significant
travel disruptions over these higher elevations.

The probability of significant ice across the CONUS is less than
10 percent.

Fracasso

$$
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FOUS11 KWBC 210718
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
218 AM EST Fri Nov 21 2025

Valid 12Z Fri Nov 21 2025 - 12Z Mon Nov 24 2025

...California & Southern Rockies... Days 1-3...

A Pacific upper low near the central CA coast this morning will
continue to drop south-southeastward today into a position just
west of the northern Baja Peninsula by early Saturday. A
combination of healthy PVA, upslope flow, and a modest moisture
feed will promote periods of snow for the southern Sierra and SoCal
ranges today (San Rafael/San Gabriel/San Bernadino/San Jacinto).
Snow levels will continue to tick downward to between 5500-6000ft.
With the upper low so far south of the region by tomorrow, the
colder temperatures aloft will be displaced southward and
diminished upslope flow will reduce precipitation rates. Snow
levels will rise and change snow to rain below 7000ft before ending
midday Saturday. The upper low will begin to push eastward
Saturday night through Sunday and spread moisture across AZ into NM
and CO with snow at high elevations (generally above 8000-9000ft).
The upper low will pick up speed Sunday evening and lift through
CO and weaken into an open wave over the High Plains by early
Monday. Along and near its path, modest snow is expected over the
San Juans and Sangre de Cristos but snow levels will remain high
through the event (no lower than about 7500ft which will be at the
end of the event).

WPC probabilities for an additional 6 inches of snow today are

50% above about 10,000ft over the southern Sierra. Across the

SoCal Mountains, with a longer duration of precipitation today, a
significant heavy/wet snowfall is likely to continue. WPC
probabilities for an additional 6 inches of snow are >50% above
8000ft. This could cause locally significant travel disruptions
over these higher elevations, along with the potential for some
tree damage and infrastructure impacts given the heavy/wet
consistency of the snowfall. The WSSI does depict some Moderate to
locally Major Impacts in the San Gabriel and San Bernadino
Mountains above 8,000ft.

In the Southern Rockies, WPC probabilities for at least 8 inches
of snow primarily on Day 3 (Sunday) are >50% above about 11,000ft
in the more remote/higher ridge lines of the San Juans and
especially the Sangre De Cristo range.

...Pacific Northwest... Day 3...

Quasi-zonal flow out of the Northern Pacific will bring in a
rather strong frontal system to WA/OR/ID and northwestern MT
Sunday. Snow levels around 5000-6000ft Sunday afternoon will drop
to below 3000ft by early Monday as precipitation lightens. Some
significant snow may impact the higher passes where WPC
probabilities for at least 6 inches of snow are >50% above about
4000-4500ft. Snow will also spread across northern ID into
northwestern MT late Sunday/early Monday with snow continuing
beyond this forecast period.

...Northeast... Day 3...

A clipper system associated with a shortwave and dip in the jet
stream will push quickly through southern Ontario/Quebec and
northern NY/New England Sunday afternoon/evening. QPF amounts
appear light, and generally only an inch of two of snow is
expected. WPC probabilities for at least 4 inches of snow are less
than 10 percent, though the NBMexp (v5.0) probabilities max out
between 15-25% over the northern Green Mountains of VT.


The probability of significant ice across the CONUS is less than
10 percent.

Fracasso


$$
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FOUS11 KWBC 220732
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
232 AM EST Sat Nov 22 2025

Valid 12Z Sat Nov 22 2025 - 12Z Tue Nov 25 2025

...Southern Rockies... Days 1-2.5...

An upper-low just west of Baja California will move eastward today
and northeastward tonight, spreading rain and high mountain snow
across AZ then into CO/NM tomorrow. Healthy subtropical moisture
will be directed at the Southern Rockies at the same time as
diffluent flow aloft supports upper-level ascent atop the
atmosphere. Upslope enhancement into some of the mountain ranges
such as the Gila Mountains, the San Juans, and the Sangre De Cristo
will aid in producing modest snow totals for the mountain peaks.
The upper low will cross over the Four Corners region and bring
heavier snow to the San Juans and Sangre de Cristos, but at high
elevations. Snow will taper off on Monday as the upper low slowly fills.

Given the lack of a cold antecedent air-mass, snow levels will
struggle to dip much lower than 7,000ft. Elevations above 9,000ft
in the Mogollon Rim and Gila Mountains and the more remote
elevations above 10,000ft in the San Juans and Sangre De Cristos
will see the heaviest snow. WPC probabilities for at least 8 inches
of snow are >50% above about 11,000ft in the more remote/higher
ridge lines of the San Juans and Sangre De Cristo range. WPC
probabilities are low-to-moderate (20-50%) for storm total snowfall

8" over the White Mountains in eastern AZ.

...Pacific Northwest & Northern Rockies... Days 1-3...

A Pacific disturbance embedded within quasi-zonal flow will usher
in a progressive, but potent, frontal system into WA/OR/ID and
northwestern MT Sunday. As the cold front traverses the Pacific
Northwest, snow levels around 5000-6000ft Sunday afternoon will
drop to as low as 2,000ft on the windward side of the Cascades by
early Monday as precipitation begins to taper off. WPC
probabilities for >4" of snow do range between 30-60% in both
Stevens and Snoqualmie Passes, with potentially upwards of 6" possible.

Snow will also spread across northern ID into northwestern MT late
Sunday and through Monday as moisture associated with the Pacific
system moves through. Additional heavy snowfall along the Lewis
Range on Monday may be enhanced by easterly upslope flow due to
strengthening high pressure to the north. WPC probabilities for at
least 8 inches of snow are >50% across the Lewis Range and above
7000ft where more than a foot of snow is possible at the highest
elevations.

...Northeast... Day 2...

A clipper system rotating beneath the base of an broad upper-low
over Quebec will push quickly through northern NY/New England
Sunday afternoon/evening and exit to the east by Monday morning.
QPF and therefore snowfall may be somewhat limited due to its fast
movement, but some upslope enhancement may yield a bit more than
2-3" of snow across the Tug Hill, Adirondacks, and both the Green
and northern White Mountains. WPC probabilities for at least 4
inches of snow are low (10-40%) in these areas generally above
15000-2000ft.

The probability of significant ice across the CONUS is less than 10 percent.

Fracasso/Mullinax

$$
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FOUS11 KWBC 230758
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
258 AM EST Sun Nov 23 2025

Valid 12Z Sun Nov 23 2025 - 12Z Wed Nov 26 2025


...Southern Rockies... Day 1...

An upper-low over central AZ this morning will move across the
Four Corners and through Colorado later today. Diffluent flow atop
a robust subtropical moisture feed will promote snow across the San
Juans and Sangre de Cristos, aided by upslope enhancement as the
upper low approaches. Snow levels will be high -- generally above
9000ft initially then dropping to around 7000ft as precipitation
ends early Monday. WPC probabilities for at least 8 inches of snow
are >50% above about 11,000ft in the more remote/higher ridge lines
of the San Juans and Sangre De Cristo range.

...Pacific Northwest & Northern Rockies... Days 1-2...

A Pacific disturbance embedded within quasi-zonal flow will usher
in a progressive, but potent, frontal system into WA/OR/ID and
northwestern MT this morning. As the cold front traverses the
Pacific Northwest, snow levels around 5000-6000ft this afternoon
will drop to as low as 2,000ft on the windward side of the Cascades
by early Monday as precipitation begins to taper off. This would
affect many of the passes with at least some snow, and WPC
probabilities for >4" of snow are between 30-50% in both Stevens
and Snoqualmie Passes.

Farther east, snow will also spread across northern ID into
western MT later today through Monday as moisture associated with
the Pacific system passes through. Minor snowfall accumulations
(1-4") are possible as far south as the Tetons and Big Horns. The
focus for the heaviest snowfall resides along the Lewis Range on
Monday as snowfall rates become enhanced by easterly upslope flow
due to strengthening high pressure over southwest Canada. Snowfall
rates nearing >1"/hr are possible at higher open passes (e.g.,
Marias Pass). Snow should taper off across all of the northern
Rockies by early Tuesday morning. WPC probabilities for >8" of
snowfall are >70% across the Lewis Range above 5,000ft. In the
highest elevations of the Lewis Range (>6,000ft), WPC probabilities
show moderate chances (40-70%) for snowfall totals >12". The WSSI
does show mostly Minor Impacts in the Lewis Range, the Bitterroots,
and the Crazy Mountains.

...Northern Cascades/Olympic Peninsula... Day 3...

The next Pacific system will move into western Washington on
Tuesday on a 120kt jet. Cold air in place could support some spotty
freezing rain along/east of the crest as warmer air aloft moves
in. Snow levels will slowly rise as the warm front lifts through
overnight into early Wednesday, but may be loathe to budge east of
the Cascades until later on Wednesday. With a fairly long moisture
fetch into the Pacific, precipitation amounts could be at least
modest, suggesting impactful snow even at Snoqualmie Pass. Through
12Z Wednesday, WPC probabilities of at least 6 inches of snow are

50% above about 5000ft.

...Northeast... Day 1...

A clipper system rotating beneath the base of an broad upper-low
over Quebec will push quickly through northern NY/New England this afternoon/evening and exit to the east by Monday morning. QPF and
the resulting snowfall will be somewhat limited due to its fast
movement and the clipper being relatively moisture-starved, but
some upslope enhancement may allow for anywhere between 1-4" of
snow across the Tug Hill, Adirondacks, and the Green and northern
White Mountains. WPC probabilities for at least 4 inches of snow
remain on the lower side (10-40%) in these areas generally above
1500-2000ft in the Adirondacks and Tug Hill, with the highest peaks
showing a slightly higher change (50-60%) of at least 4 inches of
snow. Still, some snow covered roads could make for slippery
driving conditions tonight and Monday morning.

...Northern Plains... Day 3...

The shortwave trough responsible for the snow across the Northern
Rockies to start the week moves into the northern High Plains on
Monday night. By early Tuesday, a sharpening of the jet will allow
the mid-level shortwave to deepen and close off (at least briefly)
as it remains progressive. WAA and lower-level FGEN will support a
stripe of light to modest snow across ND as a surface low deepens
along the ND/SD border. It will then continue to strengthen and
lift northeastward through MN into the western Great Lakes, with
sufficiently cold air on its northwest side for a broad area of
snow. The wrapped-up system could form a TROWAL across northern MN,
favoring a region of heavier snow. The models disagree on the
location and amount of QPF (and thus snow), but the potential
exists for an axis of appreciable snow late Tuesday into Wednesday
(and beyond for the western Great Lakes).

Through 12Z Wednesday, WPC probabilities for at least 4 inches of
snow are >50% from northeastern MT across much of ND and northern
MN. Within this region, probabilities for at least 8 inches of snow
are 30-50% over central ND and northern to northeastern MN.
Blowing snow may become a hazard as winds increase in response to
the deepening low pressure. Interests in the Northern Plains and
Upper Midwest should keep a close eye on the forecasts from their
NWS WFOs and WPC in the coming days given this storm could prove a
headache for those traveling in the lead up to Thanksgiving.

The probability of significant ice across the CONUS is less than 10 percent.

Fracasso/Mullinax

$$
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FOUS11 KWBC 240813
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
313 AM EST Mon Nov 24 2025

Valid 12Z Mon Nov 24 2025 - 12Z Thu Nov 27 2025

...Northern Rockies... Day 1...

Shortwave over Washington this morning will carry a cold front
through the Northern Rockies today. The strongest height falls will
cross through northwestern MT around Glacier NP with modest snow
above 5000-6000ft. WIth the moisture feed stretched back (but
weakening) to the Pacific, snow will fall as far south as the
Bitterroots and into northwestern WY where amounts will be lower (a
few inches). Snow will taper from west to east this afternoon
through this evening as the cold front makes steady progress
through the region. WPC probabilities for at least 8 inches of snow
are >50% above about 5000ft.

...Pacific Northwest/Northern Rockies... Days 2-3...

The next Pacific system moves into western WA on Tuesday at the
nose of an 140kt 250mb jet. Colder air in place ahead of the
moisture may support some spotty freezing rain along the leeward
slopes/valleys of the Cascades and in the valleys of the Columbia
River Basin over northern WA. Snow levels will gradually rise as
the warm front lifts through Tuesday night into early Wednesday,
but the surface front will takes longer to cross the Cascades
rather than the more robust 700mb WAA nose that support the
potential for icy conditions east of the Cascades. Thanks to a
longwave trough firmly entrenched over the North Pacific, an
extended moisture fetch into the the Pacific Northwest will support
a more or less continuous stretch of mountain snow over the
Cascades and downstream into the Northern Rockies through the end
of this forecast period (then continuing into the medium range).
Snow levels will vary, starting around 2000-4000ft then rising to
around 5000-7000ft as milder air moves in. WPC probabilities for at
least 8 inches of snow are >50% above about 5000ft. Both
Snoqualmie and Stevens Pass may see multiple inches of snow before
snow levels rise above the passes early Wednesday.

...Northern Plains/Upper Midwest/Upper Great Lakes... Days 1-3...

The shortwave trough exiting the Northern Rockies this afternoon
will move into the northern High Plains tonight. The upper jet
across the US/Canada will sharpen and support a strengthening area
of low pressure that will move from the Plains to the Upper Midwest
and western Great Lakes over the next few days. Tonight, an 850mb
low will form along a strengthening 925-850mb front over central
ND, while a narrow inverted trough axis forms on its western flank.
By 12Z Tuesday, bands of moderate to heavy snow are likely from
northeastern MT to central ND with increasingly gusty winds as the
low pressure strengthens. Tuesday afternoon the low over
southeastern MN will start to deepen quickly as the mid-level
shortwave starts to close off, allowing a TROWAL to form on the
western side of the storm. This could allow for >1"/hr snowfall
rates along with gusty winds over 30mph, causing blowing/drifting
snow. Some areas closer to Lake Superior and over central MN will
see marginal temperatures and snow may not accumulate quickly if
the rates are not high, though colder air will eventually win and
change all areas to snow overnight into early Wednesday as the low
moves into the U.P. of Michigan and deepens into the mid 990s mb.
By Wednesday night into early Thursday, the system will reach its
peak intensity over Ontario and take the bulk of its snow with it.
However, northerly to northwesterly flow will transition the lake-
enhanced snow to lake effect snow over northern WI into the U.P.
where the 850-lake temperature difference will be >15C (-10 to -14C
at 850mb and a lake temperature around 5C). Lake effect snow will
eventually break out across the rest of the Great Lakes by Thursday
morning and continue into the medium range period.

WPC probabilities for at least 4 inches of snow are >50% from
northwestern ND to central MN then eastward through the Arrowhead,
northern WI, and across much of the U.P. of Michigan. Within this
areas, probabilities for at least 8 inches of snow are >50% over
northeastern MN due to the synoptic system itself. Across northern
WI and into the U.P., the combination of synoptic snow and then
lake effect snow will boost totals well over a foot. There, WPC
probabilities for at least 18 inches of snow are >50% from near
Ironwood northeastward across the northern portion of the U.P. near
the Huron Mountains.

The probability of significant ice across the CONUS is less than 10 percent.

Fracasso

$$
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FOUS11 KWBC 190744
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
244 AM EST Fri Dec 19 2025

Valid 12Z Fri Dec 19 2025 - 12Z Mon Dec 22 2025

...Great Lakes & Northern New England... Days 1-2...

Negatively tilted upper trough and associated strong cold front is
expected to swing across the Great Lakes and East Coast today
producing a rapid drop in temperatures and gusty winds. This setup
will also provide the opportunity for heavy lake effect and upslope
snow. 850 mb temperatures as low as -15C to -20C are expected
behind the strong cold front as lake temperatures remain largely
around 5C. This temperature delta and brief surge of west-
northwesterly flow will allow for heavy lake effect snow in the
typical snowbelts downwind of Lake Superior and Michigan, with
additional heavier snow possible downwind of Lake Erie and Lake
Ontario given the greater westerly component to the low-level
winds. The highest WPC probabilities for at least 6" of snow
through Saturday morning is across the Tug Hill Plateau downwind of
Lake Ontario, where chances sit at 70-90%. Additionally, some
light to moderate upslope post-frontal snowfall is possible along
the central Appalachians and northern New England elevated west-
northwest facing terrain. Here, WPC probabilities for at least 4
inches of snowfall through 18z Saturday range between 30-60%.

...Cascades, Northern Rockies, & Northern California... Days 1-3...

An anchored -WPO/-PNA teleconnection pattern is the culprit in the
endless barrage of atmospheric rivers and moist Pacific flow into
the western U.S. This will feed copious amounts of snow throughout
the mountains of the Pacific Northwest and stream as far east as
the northern Rockies. The strongest IVT signal shifts southward
over the next few days and focuses over southern Oregon and
especially northern California this weekend. It is within this
moisture plume where the highest snow levels above 8000-9000ft
reside, with much lower snow levels to the north across the Pacific
Northwest on Day 1 around 1000-2000ft. These lower snow levels
also overspread the northern Rockies by the end of Day 1 after
starting in the 5000-6000ft range within the core of the ongoing
Atmospheric River. For the Tetons, Absaroka, and Wind River Ranges,
this region will reside closer to stronger 700mb jet and anomalous
PWATs (>99th ECMWF climatological percentiles through Friday
afternoon), giving these ranges both an abundance of moisture and
strong upslope enhancement to keep heavy snow in the forecast
through Saturday morning for elevation at and above 7000ft. For
northern CA, snow levels dip below 5,000ft in the Siskiyou and
Shasta, but as precipitation also wanes. These levels rise once
again above 6000-7000ft with the next AR on Sunday.

The lone exception to the higher snow levels will be ongoing
westerly upslope flow into the WA Cascades as low pressure lingers
off the coast of British Columbia. Snow levels are also expected to
remain quite low and around 1,500ft on Saturday and 2,500 ft on
Sunday. The bulk of the heaviest snowfall in the WA Cascades and
Olympics is expected above 2500ft. WPC 72-hour probabilities show
high chances probabilities (>70%) for snowfall totals >18" between
3,000- 4000ft, while similar high chance probabilities exist above
4,000ft for snowfall totals >30". In the Rockies, high chance
probabilities (>70%) for >12" of snow on Day 1 are present above
5,000ft in the Blue Mountains, Bitterroots, and the Lewis Range,
while those same probabilities for >18" are present above 6,000ft
in the Sawtooth. Snowfall in the Tetons and Wind River Ranges are
likely to range between 1-3 feet with some localized amounts
approaching 4 feet in the more remote reaches of these ranges
including the next round on Sunday. The WSSI is keying in on
Extreme Impact potential (extremely dangerous travel, damages to
infrastructure in the Wind River, Teton, and Absaroka ranges
through Friday night, largely in the higher reaches of these
ranges. Still, Major Impacts (significant travel disruptions) at
intermediate elevations of these ranges are likely with heavy snow
and whiteout conditions contributing to the impacts in these ranges
to close out the week.

...Sierra Nevada... Days 2-3...

Precipitation along the southern periphery of the AR plume begins
to sink southward towards the central Sierra Nevada by the end of
Day 1, but with snow levels near 9000ft. Multiple AR impulses
through early Monday are expected with snow levels potentially
dropping down to around 8000ft as these moisture plumes are aimed
at the northern/central Sierra Nevada. WPC probabilities for at
least 12 inches of snowfall on days 2-3 (ending 12z Monday) are
between 50-70% and primarily above 9000ft elevation. This is
possibly the start of a very active and impactful weather pattern
across California, with additional high elevation heavy snow likely
through the middle to end of next week.

The probability of significant icing is less than 10 percent.

Snell
$$
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FOUS11 KWBC 300711
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
211 AM EST Tue Dec 30 2025

Valid 12Z Tue Dec 30 2025 - 12Z Fri Jan 02 2026

...Great Lakes, Central Appalachians, Interior Northeast...
Days 1-3... Maximum impact level from WSSI: Moderate to Major

Deep upper troughing will linger over southern Hudson Bay/James
Bay for the next few days, maintaining broad cyclonic flow out of
central Canada and across the Great Lakes. This will result in a
mostly continuous period of lake effect snow downwind of all Great
Lakes but focused especially east of Lakes Erie and Ontario. Two
mid-level shortwaves will zip through the southwest/southern base
of the trough which will act to disrupt the banding and also infuse
a bit more lift and moisture to the region. With lake temperatures
in the 30s to 40s and 850mb temperatures -15 to -20C, sufficient
lift will be generated over the lakes on a general NW to W flow
from the Upper Lakes to Lower Lakes, respectively. This will set up multi-banded snows over Michigan with multi to strong single
banded snows over NW PA, western NY, and between Syracuse and
Watertown. The bands will modulate due to the shortwaves moving
through the region, with the first tonight and the second Wednesday
with perhaps a third weaken one overnight Thursday. The passage of
the second shortwave and associated surface arctic front may also
bring the threat for snow squalls tomorrow afternoon into the
overnight (New Year's Eve) from Michigan to Ohio to Pennsylvania
per the Snow Squall Parameter.

In addition to the lake effect snows, strong upslope ascent into
the central Appalachians will favor at least modest totals over
eastern WV northward through western MD and into the Laurel
Highlands in PA, especially Wednesday into Thursday.

WPC's 72-hour snowfall probabilities show high chances (>70%) for
snowfall totals >18" in NW PA and along the Chautauqua Ridge in
southwestern NY into some of the Buffalo Southtowns. Localized
amounts could exceed 2-3ft. Just east of Lake Ontario, WPC
probabilities show moderate-to-high chances (50-70%) for snowfall
totals >18" in the region between Syracuse, Watertown, and east of
Rochester (centered around Oswego). Over Michigan, totals will
likely be lower, but still appreciable. WPC probabilities for at
least 8 inches of snow are highest (>50%) near/southwest of the
Keweenaw Peninsula, the eastern U.P., and over northwestern Lower
Michigan. Farther south, WPC probabilities for at least 8 inches of
snow are highest over eastern WV northward to the Laurel Highlands
in PA. Light to perhaps modest snow is also possible into the
Green Mountains in VT via upslope flow.

...Sierra Nevada to the Central Rockies... Days 2-3...
Maximum impact level from WSSI: Minor to Moderate

A deep trough in the subtropical Eastern Pacific will lift toward
California and weaken on Wednesday, spreading generally light to
moderate QPF over the region. Snow levels will be high

9000-10,000ft) where more than 8 inches is likely above 10,000ft

through Thursday night. Lighter precipitation will spread
northwestward through Utah to the CO Rockies amid high snow levels (8000-9000ft) and generally near to under 6 inches of snow.

Fracasso

$$
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FOUS11 KWBC 010834
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
334 AM EST Thu Jan 1 2026

Valid 12Z Thu Jan 01 2026 - 12Z Sun Jan 04 2026

...Eastern Maine... Day 1...

Potent upper trough will swing across New England today, with an
embedded vorticity maxima lifting into the Canadian Maritimes
Thursday night. The evolution of this vorticity max combined with
at least the distant LFQ of a southeast diving upper jet will allow
a surface low to deepen as it tracks across Northern New England,
intensifying more rapidly in response to a negative tilt of the
upper trough this evening into Canada. While in general this
system will be progressive, an inverted trough positioned west of
the primary low will rotate across eastern Maine as the low shifts
northward, leading to a longer duration of moderate to heavy
snowfall rates (30-50% chance of 1"/hr). This will result in a
swath of moderate snowfall accumulations for which the WPC
probabilities indicate has a moderate chance (50-70%) of exceeding
6 inches, highest across Downeast Maine.

...Great Lakes... Days 1-3...

An arctic front passing east of the Great Lakes early this morning
will leave impressive CAA in its wake, while cyclonic flow asserts
itself across the region. This cyclonic flow will be secondary
enhanced late Thursday night into Friday as another shortwave
passes through the flow, leading to renewed CAA before shortwave
ridging develops by the end of the forecast period.

While this arctic front will maintain a snow-squall risk through
early this morning into New England and the Mid-Atlantic (for which
Key Messages remain in effect, linked at the bottom of this
discussion) the primary hazard becomes widespread heavy lake effect
snow (LES) in the favored W/NW snow belts. The most intense LES
will likely begin late tonight as 850mb temperatures plummet to as
low as -15C to -20C, across lakes that, while they have cooled,
are mostly ice-free. This will lead to impressive SBCAPE as high
5000-1000 J/kg to support a long duration 1-2+"/hr LES event,
especially downwind of Lakes Erie and Ontario due to upstream
connections. The heaviest accumulations D1 and D2 are expected
across the Chautauqua Ridge and along//just barely south of the
Tug Hill plateau before shifting a little south into D2. WPC
probabilities are high (>90%) for 6+ inches in these areas D1,
continuing east of Lake Ontario D2. Locally 2-4 feet of snow is
possible east of Lake Ontario before LES wanes during D3. Downwind
of the other Great Lakes, WPC probabilities D1 feature a moderate
risk (50-70%) for 6+ inches in the eastern U.P., but this wanes
quickly during D2.

...California through the Central Rockies... Days 1-3...

A deep trough in the subtropical Eastern Pacific will lift
NNE through the central CA coast early today before crossing the
Sierra Nevada and into the Great Basin by Friday morning. The
primary shortwave within this trough will crest an expanding ridge
(amplifying downstream of a more intense trough over the Pacific)
and drop into CO and the High Plains Friday morning/aftn.,
As the trough moves inland, snow levels on the Sierra Nevada will
fall to around 7500ft this afternoon, bringing heavy snow until
precipitation ends this evening. Farther east, and continuing
downstream of this trough/impulse, snow levels will remain elevated
at 7000-8000 ft, but precipitation falling as snow will spread
across much of the Great Basin and Four Corners at the higher
elevations. WPC probabilities D1 for 6+ inches of snow reach above
70% in the Sierra, and locally as high as 70% in portions of the
Wasatch and CO Rockies. Precipitation will linger through D2 across
the Four Corners terrain, but with generally a waning trend.

Then on D3 a more pronounced surge of precipitation spreads onshore
CA once again as a deep trough amplifies offshore, resulting in
impressively amplified southerly flow. This will push moisture
onshore as IVT exceeds 500 kg/m/s (>80% chance). Once again snow
levels will be elevated within the accompanying WAA, reaching as
high as 8000 ft into the Sierra (although much lower around 6000 ft
across the Shasta/Trinity region). The pronounced moisture will
result in heavy snow again above these levels, and with SLR
expected to be low, it will be an impactful snowfall due to snow
load. WPC probabilities D3 are high (>90%) for more than 6 inches
across these mountains, with locally more than 12 inches possible
(30-50% chance) in the Sierra.

...Columbia Basin and Gorge... Day 1...

Increasing southerly mid-level flow over the Pacific Coast will
spread moisture northward, aided by a weakening shortwave lifting
from CA into the northern Great Basin. As this moisture spreads
into the Pacific Northwest, it will overrun a slowly retreating
ridge of high pressure, manifesting with easterly winds draining
into the Columbia Basin/Gorge to maintain cold surface air. This
setup is favorable for light freezing rain with modest accretions
as reflected by WPC probabilities that reach as high as 70% for 0.1
inches of ice. Although amounts are generally light, impacted
travel is likely tonight into Friday morning due to slippery
roadways.

Weiss

...Winter Storm Key Messages are in effect. Please see current
Key Messages below...

https://www.wpc.ncep.noaa.gov/key_messages/LatestKeyMessage_1.png

$$
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FOUS11 KWBC 020753
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
253 AM EST Fri Jan 2 2026

Valid 12Z Fri Jan 02 2026 - 12Z Mon Jan 05 2026

...Great Lakes... Days 1-3...

Ongoing lake effect snow (LES) Will continue in earnest today,
especially across the eastern U.P., and downwind of Lakes Erie and
Ontario. This LES will be driven by persistent CAA across the
lakes, leading to steep lapse rates and inversion depths that climb
towards 800mb, leading to 500-750 J/kg of lake-induced instability.
While the mean low-level flow will be a bit more W than NW, this
will help tap an upstream connection from Superior, across Huron,
and towards Lake Ontario, indicating the heaviest snowfall will
likely be along and south of the Tug Hill Plateau through D1 and
into D2 before winding down in response to brief shortwave ridging.
While periods of heavy snow are also likely in portions of the
northern L.P. and along the Chautauqua ridge, the persistence and
intensity of this snowfall should be less. This is reflected by WPC probabilities for 4+ inches on D1 that area 30-50% in the eastern
U.P. and along the Chautauqua Ridge, but above 90% east of Lake
Ontario, where locally 2+ feet is likely on D1. During D2 the
intensity and coverage of LES wanes, but WPC probabilities for 4+
inches remain above 50% near Oswego, NY.

After a brief respite in response to the aforementioned shortwave
ridging, two separate, but fast moving, shortwaves will crest the
ridge to the west and dive rapidly from Saskatchewan/Alberta across
the Great Lakes. The first of these will race southeast Saturday
aftn/night, and while some enhanced ascent and subtly increased
moisture will result in light synoptic snowfall, additional
accumulations from eastern MN through western NY should be minimal.

A more substantial impulse will then drop southeast in a similar
fashion Sunday night, but this impulse will be accompanied by
greater moisture as it originates from the Pacific and ejects from
the Northern Plains rather than central Canada. This will again be
fast moving, but will have more pronounced synoptic lift in
response to height falls, PVA, LFQ jet diffluence, and more robust
850mb WAA leading to enhanced fgen. At this time, the speed of the
system is expected to limit total snowfall, but briefly heavy snow
rates thanks to idealized ascent into the DGZ could produce a
narrow swath of more than 4 inches as reflected by WPC
probabilities that are as high as 50-70% for 4+ inches from near
Duluth, MN eastward through much of the U.P and the neighboring
portions of WI.

...Western U.S. Mountain Ranges... Days 1-3...

An active period of weather continues across much of the West as
Pacific moisture repeatedly surges onshore in response to
persistent troughing offshore.

For D1, a brief period of ridging will blossom along the Pacific
Coast, but downstream into the Intermountain West a shortwave with
Pacific origin will lift steadily northeast while de-amplifying.
This will result in a stripe of precipitation arcing from the
Northern to the Central Rockies, and falling as snow above
6000-7000 ft. WPC probabilities D1 reach above 70% for 6+ inches
near the Tetons of WY and the Park Range of CO, with more
widespread elevated probabilities for 4+ inches across much of the
rest of the terrain in this region.

Then beginning late D1 and continuing into D3, much more pronounced
moisture begins to pivot onshore the Pacific Coast. This will be in
response to an impressive trough aligned just offshore, from which
a surface low will track northeast towards WA state by Sunday
morning, with a secondary wave tracking towards northern CA Sunday
aftn. While these surface lows will help enhance local ascent, in
general moisture will be pronounced across much of the West due to
increasing southerly flow downstream of the primary trough axis
pushing IVT well onshore with magnitudes above 500 kg/m/s. As is
typical with strong IVT plumes, they will be driven both by Pacific
jet energy and warm advection, resulting in elevated snow levels
climbing to 7000-9000 ft ahead of the first wave, and while they
will rise again with the secondary wave, they will generally be
much lower, 5000-7000 ft on D3, even lower, around 3500 ft, in the
Cascades and interior Northwest.

Any ascent forced through synoptic features or upslope enhancement
will cause rounds of heavy snowfall above these elevations both
Saturday and Sunday. WPC probabilities steadily increase and expand
through the weekend, with widespread high chances (>70%) for 4+
inches reaching from the Olympics, along the entirety of the
Cascades, the Shasta region, the Sierra, and through much of the Northern/Central Rockies and into the Wasatch, by Monday morning.
While the heaviest snowfall is likely in the Sierra where many
locations above 6000 ft could experience 2-5 feet of snow, much of
the higher terrain of the West could receive 1-2 feet before
coverage wanes just beyond D3. This will likely bring considerable
impacts to the higher elevations due to generally low SLR snow,
with difficult travel likely across the Sierra Passes.

...Central Plains... Day 1...

A fast moving clipper rounding the western ridge and dropping
southeast over the Central Plains today will be of subtropical
origin. Although this feature will be progressive and of modest
amplitude as it weakens, it will produce sufficient ascent into a
moistening column to produce a narrow corridor of mixed
precipitation in the vicinity of northeast Nebraska. While total
precipitation will be modest, WPC probabilities indicate a 70-90%
chance of at least 0.01" of freezing rain, with locally up to 0.1"
of ice possible leading to hazardous travel.

Weiss
$$

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FOUS11 KWBC 040819
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
319 AM EST Sun Jan 4 2026

Valid 12Z Sun Jan 04 2026 - 12Z Wed Jan 07 2026

...Northern Plains/Upper Midwest/Great Lakes/Interior Northeast...
Days 1-3...

Some modest lake effect snow (LES) will continue through Sunday
aftn, but primarily within a single band south/southeast of Lake
Ontario with upstream connection to Lakes Huron and Superior.
Additional snowfall across this region should be light as reflected
by WPC probabilities for an additional 2+" of just 10-30%,
although brief 1"/hr rates are possible (10-30% chance).

Thereafter, the mid-level pattern flattens a bit as shortwave
ridging expands from the west, leading to pinched and more
progressive flow across the region. Within this flow, two back-to-
back shortwaves will traverse the region bringing rounds of wintry weather.

The first of these will emerge from the High Plains Sunday morning
and push due east across the Great Lakes in a de-amplifying manner
as it becomes absorbed into the pinched westerlies. Despite the
weakening amplitude, height falls, PVA, and the left-exit region of
a strengthening jet streak will produce deep layer ascent, and
the intensification of this jet streak will likely result in
enhanced omega despite the weakening amplitude of the shortwave. At
the same time, increasing and impressive 925-850mb WAA will spread
northeast ahead of this impulse, aligning with the best left-exit
dynamics and the associated response to produce impressive fgen but
with limited temporal duration. Since this feature will be of
Pacific origin, the accompanying moisture will be impressive as
reflected by NAEFS PWs that are above the 97th percentile, aligned
with the strongest ascent. This suggests that as precipitation
expands from MN through the U.P., and into the northern L.P., a
narrow band of heavy snow will develop which has a 60-80% chance
of producing 1"/hr snowfall rates. The duration of these will,
again, be limited to the progressive nature of the wave, but WPC
probabilities for 4+ inches are above 50% from the Arrowhead of MN
eastward through the northern L.P. of MI, with locally 6-8"
possible (30% chance) in portions of the eastern U.P.

Additionally, south of this axis of heavy snow, a corridor of
modest mixed precipitation, including freezing rain, is likely as
the WAA surges a warm nose to around +3C at 850-800mb. The
refreezing layer is quite deep, so this may manifest more as sleet
than freezing rain, but hazardous travel is Sunday evening from MN
through central WI where WPC probabilities for 0.01" of ice are 50-70%.

This lead wave will continue to track into New England before
exiting to the Atlantic Monday night, but additional snowfall is
expected to be light, generally 1-3", although locally higher in
the Tug Hill Plateau through lake enhancement, as ascent weakens.

The next shortwave follows quickly in the wake of the first, and
emerges from CA Sunday evening before racing to reach the Corn Belt
by Tuesday morning. This impulse will track along the southern
subtropical jet, which is progged to intensify over the Central
Plains, reaching towards 140 kts. The favorable overlap of the LFQ
and height falls downstream of the shortwave will likely lead to
surface low pressure development Monday night near Iowa, with this
low then tracking steadily northeast into Ontario by Tuesday
evening. While there is still some spatial spread in the placement
of this low according to the different ensemble clusters, the
increasing ascent will lead to another round of wintry
precipitation from Minnesota through the Great Lakes (where a mix
of freezing rain and snow is likely), with additional mixed
precipitation spreading into New England by the end of the forecast
period. Total ascent with this secondary wave should be less
intense than the lead wave, and the thermal evolution is quite
complex due to potential secondary low development in the Gulf of
Maine, but at this time WPC probabilities for 2+ inches of snow are
just 10-30% in the higher elevations of Upstate NY and northern New England.

For the freezing rain, WPC probabilities indicate a high risk

70% chance) of at least 0.01" of ice from central MN near the

Twin Cities through much of WI and MI, and into central and
northern New England. The greatest risk for at least 0.1" of ice is
likely in parts of northern WI, northern MI, and the higher
elevations of the Catskills, Adirondacks, and southern Greens.

...Western U.S. Mountain Ranges... Days 1-2...

The active west continues into early next week as an anomalous
trough persists just off the Pacific coast through Tuesday morning
before amplifying into a closed low which then undercuts towards
Baja by the end of the forecast period.

Downstream of this trough, nearly continuous S/SW flow will shed
spokes of vorticity onshore, with the accompanying height falls/PVA
leading to rounds of precipitation across much of the western
CONUS. At the same time, a subtropical jet will amplify and waver
from CA through the Central Plains, providing additionally enhanced
ascent. The combination of persistent SW mid-level flow with the
wavering jet stream will surge periods of elevated IVT onshore,
resulting in PW plumes that occasionally exceed the 90th
climatological percentile. While there may be periods of enhanced
ascent locally across different regions, in general the next 48
hours appear to be synoptically forced with broad large-scale
ascent, locally enhanced through PVA where the vorticity lobes
stream overhead, and through upslope enhancement. The strongest
upslope flow continues to be appear focused over the Sierra where
snowfall will be prolific, but heavy snow is likely through Monday
night across much of the region.

With broad SW flow encompassing the region, the accompanying WAA
will surge snow levels to as high as 6000-8000 ft in the Great
Basin and Rockies D1 (but generally 3000-5000 ft elsewhere), before
steadily falling through D2 as a cold front pushes eastward and the
trough axis finally swings farther east to the coast. By 12Z
Tuesday, snow levels are expected to be generally 1500-2500 ft in
the north, to 5000-6000 ft in the south. 2-day WPC probabilities
(12Z Sunday through 12Z Tuesday) feature a high risk (>70% chance)
for 12+ inches in the Sierra, northern CA ranges, Uintas, Tetons,
Wind Rivers, and portions of the Salmon River/Sawtooth/Bitterroots,
with lesser snowfall expected at the other regional terrain. In
the Sierra, 2-4 feet is possible in the higher elevations.

...Cascades... Day 3..

Mid-level flow across the Northern Pacific will become pinched and
zonal Tuesday, while a weak impulses approaches the coast and may
move onshore overnight into Wednesday morning. This zonal mid-level
flow will be topped by a strengthening Pacific jet streak which
will drop gradually southward such that the overlap of PVA/height
falls will match the greatest LFQ diffluence to provide ample
ascent. This will be aided by upslope enhancement into the terrain
thanks to the westerly flow, producing brief but impressive deep
layer lift into IVT that has a >80% chance of exceeding 250 kg/m/s.
While westerly IVT does not usually result in as impressive of
precipitation as that with a S or SW component, a fully saturated
column with steepening lapse rates will result leading to a period
of heavy snow in the Olympics and Cascades of OR and WA. Snow
levels will be generally 2000-3000 ft during this time, so pass
level impacts leading to hazardous travel are expected. WPC
probabilities for more than 8 inches of snow reach 70+%, with more
than 1 foot possible at the passes (Snoqualmie and Stevens included).

Weiss
$$
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FOUS11 KWBC 050758
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
258 AM EST Mon Jan 5 2026

Valid 12Z Mon Jan 05 2026 - 12Z Thu Jan 08 2026

...Upper Midwest/Great Lakes/Northeast... Days 1-3...

Shortwave currently over Wisconsin will track rapidly eastward
while continuing to de-amplify this morning, likely moving off the
Maine coast by Tuesday morning. The weakening trend of this impulse
driven by the absorption into more pinched westerlies will
gradually weaken ascent such that ongoing heavy snow near the Great
Lakes will transition to primarily light snow from Upstate NY
through central/northern New England. Light accumulations of 1-3"
are expected in this region, with locally as much as 4" possible in
the Tug Hill Plateau due to lake enhancement and southern Greens
thanks to upslope flow. In general, however, the most substantial
impacts from this shortwave will end before the new D1 period begins.

Almost as quickly as this first shortwave exits New England, a
second impulse following quickly in its wake will begin to
organize over the Upper Midwest Tuesday morning. This next impulse
stems from a weak vorticity lobe which ejected from the Pacific
trough late Sunday, crested the western ridge, and begins to deepen
as it moves towards the Great Lakes Tuesday. Unlike the lead
shortwave which weakens with time, this feature is expected to
gradually strengthen and gain amplitude as it moves eastward into
Wednesday. Additionally, this shortwave will be joined by an
impressive jet streak to its south (reaching 160 kts from the
Central Plains to the Ohio Valley) and accompanied by Pacific
moisture (PWs above the 90th climatological percentile according to
NAEFS). The resulting surface low which will develop will
additionally enhance ascent, and a swath of moderate to heavy
precipitation is likely from the western Great Lakes through New England.

Thermally, the environment is marginal for wintry precipitation due
to antecedent ridging aloft and strengthening WAA, so p-type from
WI, across the Great Lakes, and into at least central New England
will likely be a mix of rain, snow, sleet, and freezing rain. The
mixed precip will result in some impacts, but WSSI-P indicates only
minor impacts expected due to the progressive nature and mixed
p-type in this region. Still, WPC probabilities for ice accreting
to at least 0.1" reach 30-50% from near the Twin Cities through
central WI and into lower MI. Locally 0.2" of ice is possible, but
snow amounts are expected to be very light as the guidance has
trended a bit warmer tonight.

During D3, secondary low pressure development in the Gulf of Maine
could make snowfall and impacts a bit more impressive over New
England. While there remains considerable uncertainty into the
timing of this secondary low development, a surge of cold air
wrapping behind (and a developing in-situ CAD) should keep p-type
primarily snow in northern New England and mixed
snow/sleet/freezing rain in the higher elevations of Upstate NY and central/southern New England. This is reflected by an increase in
WPC snowfall probabilities, which, while still modest, are as high
as 10-30% D2 into D3 in the higher terrain of NH and ME. Icing to
the south of the snow may locally reach above 0.1" (30-50% chance
in the Adirondacks, Greens, and Monadnocks).

...California... Day 1...

Amplifying trough off the Pacific Coast will deepen into a closed
low today, with this closed center drifting southeast towards Baja
California by Wednesday morning. Downstream of this evolution,
continued SW mid-level flow and aligned Pacific jet energy will
pump moisture northeast, reflected by high probabilities (>80%
chance) for IVT exceeding 250 kg/m/s surging into CA. Although this
IVT will be pushed onshore via WAA, snow levels will generally
remain around 5000 ft as the WAA is offset by slowly sinking
heights downstream of the trough axis. At the surface, of wave of
low pressure will drop along the CA coast, and while there is
considerable spread in the longitudinal placement of this feature,
sufficient additional ascent into the moistening column will
result in periods of heavy snow above 5000 ft in the Sierra and
northern CA ranges D1, and WPC probabilities are high (>90%) for at
least 6 inches more of snow, with more than 12 inches possible in
the higher terrain, especially around Mt. Shasta.

...Olympics, Cascades, and Northern/Central Rockies... Days 2-3...

Mid-level flow becomes increasingly zonal across the Pacific,
directing energy and moisture into the Pacific Northwest beginning
on Tuesday. Aloft, a jet streak will intensify directly atop the
zonal mid-level flow, providing additional funneling of moisture
onshore before the jet starts to slowly sink southward on
Wednesday. This is reflected by a brief period of elevated IVT

90% chance exceeding 250 kg/m/s but less than 25% chance of 500

kg/m/s) Tuesday into OR/WA. As forcing for ascent increases D2 and
D3 through gradual height falls, left-exit diffluence, and
impressive upslope into the Olympics, Cascades, and Northern
Rockies, heavy snowfall will result in these areas, with snow
levels Tuesday 2000-3000 ft, falling to as low as 1000 ft late
Wednesday (higher but still just around 2500 ft in the Central Rockies).

This cooling column, increasing ascent, and impressive moisture
indicates that heavy snowfall will become increasingly widespread
above these snow levels, especially in the upwind regions of the
Olympics, Cascades, and Northern Rockies. Forecast soundings
suggest steepening lapse rates up to as high as 750mb, which
indicates accumulating snow could occur even lower than these snow
levels, and the NBM 10th% fall to as low as 500 ft in the Pacific
Northwest, so lowland snow is possible late in the forecast period.
However, the most significant accumulations, which are likely to
be impressive, will be above 2000 ft, but will encompass most of
the Cascade and Northern Rockies Passes leading to challenging
travel later this week. WPC probabilities D2 for more than 6 inches
of snow are high (>70%) in the Olympics, Cascades of WA and OR,
the Northern Rockies, and as far south as the NW WY ranges (Tetons,
Wind Rivers), with 1-2 feet likely in the higher elevations of
these ranges. During D3, precip wanes a bit across the
Intermountain West, but persists in heavy fashion across the
Olympics and Cascades where WPC probabilities for 12+ inches remain
above 50%. As noted above, the falling snow levels will result in
dangerous travel across all of the important Cascades Passes this week.

Weiss
$$
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FOUS11 KWBC 060751
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
251 AM EST Tue Jan 6 2026

Valid 12Z Tue Jan 06 2026 - 12Z Fri Jan 09 2026

...Great Lakes & Northeast... Days 1-2...

Amplifying shortwave will move steadily eastward from the Great
Lakes tonight, passing off the New England coast Wednesday morning.
While the flow in which this impulse will be embedded is generally
zonal, some modest amplification is progged by the consensus, with
the subsequent height falls overlapping modest LFQ diffluence from
a jet streak to the south to enhance deep layer lift, especially in
the Northeast. This will likely result in two waves of surface low
pressure: one moving from MI into Ontario, with secondary
development occurring off the coast of Maine. The speed at which
this second low develops, as well as its latitude, will have a
strong influence on how much cold air can lock in across New
England within the in-situ wedge. While the trends in the guidance
continue to be a slightly farther south and stronger offshore low,
which will enable more cold air to lock in, mixed precip is still
likely to be the dominant p-type outside of the higher terrain and
across northern New England. This system should remain progressive
as well, limiting total impacts and amounts.

For areas that receive mostly snow (the Adirondacks and northern
New England) WPC probabilities for 4+ inches of accumulations are
modest at 10-30%, but locally reach as high as 50% in NH and ME. South
of there, a mix including freezing rain is likely, which could
produce more than 0.1" of ice (30-50% chance) highest in the
Greens, Berkshires, and Worcester Hills.

...Olympics, Cascades, and Northern/Central Rockies... Days 1-3...

A powerful storm system over southern AK will work in tandem with
an unusually strong subtropical ridge north of HI to create a
robust 160kt 250mb jet streak in the northeast Pacific. This
will transport potent IVT eastward within pinched but generally
zonal flow, reflected by GEFS probabilities that exceed 80% for 250
kg/m/s, but are less than 25% for 500 kg/m/s. This increasing
moisture, while not exceptional, will be wrung out efficiently by
PVA within shortwaves traversing the flow, the LFQ of a slowly
sinking but strengthening Pacific jet streak, and persistent, at
times continuous, upslope flow, especially in the Olympics and
Cascades. Snow levels will fall to as low as 2,000ft, although the
heavier and more impactful snow will be observed above 3,000ft.
The heaviest snowfall arrives D1, and following a brief break in
the heavier snowfall rates early Wednesday morning, another
disturbance arrives later in the day with more snow in the Cascades
and Olympics. This time, with a colder air-mass aloft, snow levels
dip to as low as 1,000ft Wednesday afternoon and continuing into
Thursday. Although snow levels remain generally at or above 1,000
ft, steepening lapse rates aloft with continued ascent could result
in locally lower snowfall, reflected by the NBM 10th percentile
snow level falling to around 600 ft. While this should still
prevent significant accumulations in the lowlands, some of the
foothills west of the Cascades could see light snowfall on D2 as well.

With snow nearly continuously falling in these ranges through
Thursday, WPC's 72-hour snowfall probabilities are quite impressive
with high chances (>70%) for snowfall totals >24" above 3,000ft in
the Cascades and Olympics, including passes such as Snoqualmie and
Stevens. At the higher elevations, 4-6 feet of snow is possible.
This snowfall, despite elevated SLRs as the column cools, will
result in dangerous travel across most Cascade Passes, with the
WSSI-P indicating a moderate threat (50-70%) of major impacts
through the Cascades. Motorists should prepare for dangerous travel
and potential pass closures this week.

Farther east into the Northern Rockies and then pivoting down to
the Central Rockies, spokes of energy within the generally zonal
flow will provide sufficient ascent to wring out moisture that
spills across the Cascades. Although snowfall farther east should
be somewhat less impressive than points west, WPC probabilities for
12+ inches during the next 3 days are high (>90%) in the higher
terrain from the Blue Mountains of OR through most of the Northern
Rockies, and down through the Tetons, Wind Rivers, and parts of the
Wasatch. Locally, 2-4 feet is possible in the highest peaks of
these ranges, and pass-level travel will also be significantly
impacted this week.

...Four Corners States... Day 3...

Shortwave digging southeast from the Pacific Northwest will amplify
rapidly as it approaches the Central Rockies, potentially closing
off over the CO/NM High Plains Thursday night. There continues to
be a lot of spread in the mid-level evolution leading to lower than
typical confidence by D3, however, the cluster analysis (from 00Z/5
which is the most recent available) suggests there is potential for
continued deepening due to more pronounced upstream ridging leading
to a deeper trough (supported by more than 60% of the members,
although many of these are from the CMCE which may be somewhat
under-dispersive at this time). However, the trends in the
incoming 00z suite suggest the trough continues to be deeper, which
may result in a more substantial winter weather event.

As the guidance has trended steadily slower and faster with this
feature, suggesting more impressive deep layer ascent, the
resulting downstream jet streak has also intensified and arced
more impressively poleward. As this jet arcs northward, the
overlap of LFQ diffluence with height falls will likely lead to lee
side cyclogenesis Thursday evening, within a column that, while
will feature generally normal to below normal PWs, will saturate in
response to increasing low- level easterly flow around the
strengthening surface low. With steep lapse rates aloft helping to
cool the column, and flow becoming increasingly favorable to
upslope into the terrain, at least light snow is becoming likely
for much of the terrain and into the High Plains of CO/NM,
including the I-25 metro which has experienced a relative dearth of
snowfall so far this season. While adjustments in the forecast are
likely, current WPC snow probabilities indicate a high risk (>70%
chance) for 4+ inches of snow across much of the CO Rockies,
including the Front Range, and portions of the Wasatch, and down to
the White Mountains of AZ. The lower elevations of I-25 and into
the High Plains have a 10-30% chance of 4+ inches, although locally
higher amounts are possible across the Palmer Divide and Raton Mesa.

Weiss
$$
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FOUS11 KWBC 070816
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
316 AM EST Wed Jan 7 2026

Valid 12Z Wed Jan 07 2026 - 12Z Sat Jan 10 2026

...Northeast... Day 1...

Amplified but progressive shortwave will track over New England 12Z
Wed - 00Z Thu, exiting quickly to the southeast of Cape Cod
tonight. The two distinct vorticity lobes embedded within this
shortwave will drive the two surface lows (one moving across far
southern Canada while a secondary low develops off the New England
coast), with a wedge in-between the two features supporting cold
air and overrunning precipitation. The primary mechanism for
precipitation development will be the PVA/height falls and
increasing isentropic ascent, especially as the secondary low
development occurs, before the flow shifts to produce NW winds and
CAA. There is still some uncertainty into exactly how strong and at
what speed this transition to CAA will occur, but the models
continue to support slightly more cold air, keeping snow the
primary p-type for northern New York and northern New England, with
a mix including freezing rain as far south as CT/RI, but even here precipitation may end as light snow as the column cools.

Overall ascent is transient and moisture is just slightly
elevated, so total accumulations are expected to be modest. This is
reflected by WPC probabilities for an additional 2+ inches after
12Z Wednesday that are 30-50% in the highest terrain of
northern/central ME, and reach above 50% for 0.01" of ice, focused
across the Worcester Hills and Monadnock Region of NH.

...Pacific Northwest, Great Basin, Northern/Central Rockies... Days 1-3...

Deep trough over the Pacific will shift its axis inland by Friday,
with longwave ridging expanding across the Pacific Coast on
Saturday. As this ridge blossoms, precipitation will finally wane
across the area, but until then an extended period of active
weather with significant snowfall will continue.

The strong jet currently in place will dig slowly southward in
tandem with an embedded mid-level impulse tracking towards the
Great Basin. This impulse will be generally within zonal flow,
although as the trough kinks to become more amplified, mid-level
divergence will also increase. Despite a weakening of the onshore
mid-level flow, the upper jet will maintain its intensity of around
100 kts, at least early D1, before weakening, providing sufficient
IVT to fuel heavy precipitation from the Pacific Northwest into the
northern Great Basin and northern Rockies. Ascent will be aided
both by upslope flow and a fast moving surface cold front. Although
forcing looks generally transient, WPC probabilities D1 into D2 are
high (>70%) for more than 4 inches of snow from the Cascades
through the Northern Rockies and into the Tetons, Wind Rivers, and
Uintas, as well as the Ruby Mountains of NV. During D2, forcing
along the front pushes into UT/AZ where additional snowfall
exceeding 4" is likely (>70%) in the Wasatch and Mogollon Rim.

Behind this cold front, snow levels will crash, potentially falling
to below 1000 ft across the Pacific Northwest, while a second surge
of moisture occurs. This second moisture plume is driven by the
upstream jet streak from the primary trough axis, with the
impressive LFQ diffluence overlapping a secondary vorticity lobe
for ascent. As this rides into the Cascades, additional forcing for
lift created by upslope flow will wring out moisture as additional
heavy snowfall in the Olympics and Cascades, with moisture spilling
into the Northern Rockies as well. Notably, with this second
impulse, lapse rates are exceptionally steep beneath the core of
the mid-level trough, so any heavier rates will likely pull snow
down to around 600ft (NBM 10th% snow level), suggesting even some
light accumulations are possible in the foothills surrounding
Seattle and Portland (although the true lowlands will likely miss
out on any snow this time around). Still, the greatest impacts will
again be across the Cascades and the Passes where WPC probabilities
D2 into D3 are high (>70%) for an additional 4+ inches, with 2-day
total snowfall of 2-3 feet likely in the higher terrain, with even
1-2 feet possible at the passes.

...Four Corners into the High Plains... Days 2-3...

Elongated vorticity lobe will spin southeast from the Pacific
Northwest and amplify into deep longwave trough as it approaches
the Four Corners Thursday night. The intensity of this trough
remains uncertain as it amplifies towards the region around 12Z
Friday, but in general the trends have been for a deeper amplitude
while remaining positively tilted. At the same time, the resultant
jet streak downstream of this trough axis will deepen and pivot
northeast, reaching as high as 140 kts across the Southern Plains,
leaving favorable LFQ diffluence into the High Plains and Four
Corners. Where this jet streak overlaps with the most robust height
falls, lee cyclogenesis will likely result, likely in the northeast
plains of New Mexico as reflected by most ensemble members.

This low will move slowly Friday morning before elongating into
faster flow to the northeast by the end of the forecast period.
Before this occurs, a cold front will dig southward through the
High Plains, with the resulting wind field becoming more E/NE and
upsloping into the terrain of CO and NM. This will provide
additional ascent to the region, which will already be influenced
by favorable synoptic lift, suggesting a period of moderate to
heavy precipitation Thursday night through Friday aftn. Most of
this will fall as snow, especially as the cold front sags south and
cools the column through favorable CAA. However, there is still
uncertainty into how much snow will fall, especially from the
Palmer Divide northward where a significant 850mb moisture gradient
is expected. The ECMWF and its ensemble members are much drier
farther north than the other camps, but locations across southern
CO and northern NM have higher confidence in impactful snowfall,
including along the I-25 urban corridor. While the Palmer Divide
will likely experience significant snowfall due to the higher
elevations and more pronounced upslope, areas north of there,
including Denver, may experience lesser snow. However, in an area
that has seen very little snow so far this winter, this could
still be an impactful event for much of the region, with heavy snow
pulling northeast into OK/KS by the end of the period beneath the
upper jet streak.

Although confidence is modest for this time range, current WPC
probabilities are high D2 for at least 6 inches of snow across the
CO Rockies and into the White Mountains of AZ. Late D2 into D3 as
the surface low consolidates and upslope flow improves, WPC
probabilities indicate a greater risk, (50-70% chance), for at
least 6 inches of snow in the Front Range, Palmer Divide, Raton
Mesa, Sangre de Cristos, and into the high plains of southeast CO.

Weiss
$$
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FOUS11 KWBC 080813
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
313 AM EST Thu Jan 8 2026

Valid 12Z Thu Jan 08 2026 - 12Z Sun Jan 11 2026

...Pacific Northwest, Great Basin, Northern Rockies... Days 1-1.5...

A shortwave trough over northern CA this morning will strengthen as
it tracks south and east into the southwestern U.S.. Farther north,
a second shortwave trough over British Columbia will also dig
farther south across the northern Rockies and northeast High
Plains. Residual 700-300mb Pacific moisture will stream across the
Pacific NW and into the both the Northern Rockies and Great Basin
to continue to produce additional mountain snow through Thursday.
Snow levels in the northern Cascades and Olympics will be as low as
1,000ft today, but the heavier snowfall will remain confined to
elevations above 2,000ft. Farther east, the northern Rockies'
heaviest snowfall will be above 5,000ft and above 6,000ft in the
Great Basin. WPC probabilities show high chances (>70%) for
snowfall totals >6" for elevations above 3,000ft in the Cascades
and Olympics. Similar high chance probabilities are present in
parts of the Lewis, Bitterroots, Blue, and Teton Ranges for
additional snowfall >4". Snow will linger longest over the Cascades
and northern Bitterroots through Thursday night, but as the long
awaited upper level ridge builds in on Friday, snow levels will
rise and snow will taper off across all mountains ranges into the
start of the weekend.

...Four Corners into the High Plains... Days 1-2...

A pair of shortwave troughs will be responsible for rounds of
moderate-to-heavy snowfall over the Central and Southern Rockies,
with some snowfall into the central High Plains also expected. This
morning, a strengthening storm system over western KS and eastern
CO brought along a plume of subtropical moisture that is streaming
over the Four Corner states. Snow levels will dip to as low as
5,000ft in central CO and central UT with light snow falling in the
SLC and Denver metro areas. As this disturbance races into the
Midwest this afternoon, a second and more vigorous upper level
shortwave over the Great Basin heads east for the Four Corners
region, bringing with it not only additional Pacific moisture but
height falls, better PVA, and jet streak dynamics aloft. Guidance
shows a healthy area of 700mb Q-vector convergence shifting from
the Mogollon Rim and Wasatch this morning to the central and
southern Rockies by this afternoon, where periods of snow will
envelope most mountain ranges. Snow levels along the Mogollon Rim
will be as low as 6,000ft, while central and southern UT sees snow
levels still hovering as low as 5,000ft. The Gila Mountains and
southwest CO will also see an uptick in snowfall this afternoon
before tapering off early Friday morning.

Farther east, as the enhanced Q-vector convergence heads for the
Front Range of the Rockies and the High Plains this evening, a
closed 700mb low will develop over northern NM that gives rise to a
surface low forming in lee of the Sangre De Cristo mountains. Low-
level easterly winds over the central High Plains fosters upslope
flow into southern CO and northern NM beginning Thursday night and
peaking Friday morning as the 700mb low tracks just south of Raton
Pass. There remains some disagreement on the placement of the best
700mb FGEN as the 700mb low emerges into northeast NM and tracks
towards the OK/TX Panhandles. Where the best FGEN forcing sets up
and the strength of the 700mb low will be vital in where the
heaviest snowfall occurs and how far east away from the Raton Mesa
and Front Range the band of heavy snow can advance. Beneath the
700mb FGEN, >1"/hr snowfall rates are expected. As the 700mb low
moves northeast Friday afternoon, it will weaken and open up into a
progressive 500mb shortwave, resulting in frontolysis over western
KS that reduces precipitation rates and weakens dynamic cooling aloft.

At this time, WPC probabilities are highlighting the usual
suspects (Palmer Divide, Front Range, Raton Mesa) as having
moderate-to-high chances (>70%) for snowfall totals >4". I-25 at
Raton Pass sports moderate-to-high chances (50-70%) for snowfall
totals >6". Localized snowfall totals >8" along the peaks of the
Sangre De Cristo and Raton Mesa are possible. Farther east, WPC
probabilities show moderate chances (40-60%) for snowfall totals

4" in southeast CO , southwest KS, the far western OK Panhandle,

and the northwest tip of the TX Panhandle. The WSSI shows
widespread Minor Impacts (winter driving conditions; use caution
when driving) for much of the central High Plains with localized
Moderate Impacts possible.

...Upper Midwest & Great Lakes... Days 1-3...

An active stretch of potent storm systems will bring a wide range
of winter precip types to the Midwest and Great Lakes the
remainder of the week. The first storm system will track from KS on
north and east into IA this evening, then over northern MI by
Friday morning. Dynamic cooling beneath a coupling jet-streaks
structure is a plausible scenario from as far south and west as
eastern NE to as far north as the MI U.P.. Given the rapid
progression of the QPF shield, accumulating snow over 1" will be
tough for areas south and west of northern WI. However, over
northern WI and the MI U.P., the timing of the changeover to snow
coincides with the middle of the night, allowing for a better
chance for snowfall accumulations. Marquette's area in particular
will have better chances for accumulating snow as onshore, lake-
enhanced snowfall ensues. Snow tapers off Friday morning as the
storm races north into Ontario. WPC probabilities shows moderate
chances (>50%) for snowfall totals >4" in MI's Huron Mountains with
similar >50% probabilities for >2" extending southward into
northern WI. There is also the potential for light ice
accumulations from northern IA and southern MN to northern WI and
the western MI U.P. with WPC probabilities showing moderate chances
(40-60%) for ice accumulations over one-hundreth of an inch. Ice
accumulation could occur near the evening rush hour in southern MN
and central WI.

By Saturday night, the shortwave trough responsible for the heavy
snow in the the southern and central Rockies/High Plains heads east
towards the MS Valley at the same time as a closed 500mb low over
in Canada plunges south into the Upper Midwest. Guidance has come
into better consensus on the northern stream feature effectively
shearing the southern disturbance and becoming the more dominant
feature. As the 500mb low will direct PVA at the Great Lakes, a
strengthening wave of low pressure and 850-700mb WAA will produce a
larger shield of snow developing initially over southern WI and
northern IL. As moisture wraps northward around the deepening
850mb low over northern MI, a TROWAL will pivot over northern WI
and the MI U.P., prompting the development of heavy snow in these
areas Saturday afternoon and persisting into Saturday night. The
low will occlude over Lake Huron early Sunday morning as the
deformation zone of heavy snow pivots over the tip of MI's Mitten.
Once occluded, the upper low will weaken and move east as more
progressive flow over the Canadian Prairies kicks the storm east
into Ontario Sunday afternoon.

WPC probabilities show moderate-to-high chances (50-0%) for
snowfall totals >4" from the Green Bay area in eastern WI on north
and east through the eastern MI U.P. and the northern tier of MI's
L.P. (Lower Peninsula). The tip of MI's L.P. are favored to contend
with the heaviest snowfall given their longer duration beneath the
TROWAL and some lingering lake-enhanced snowfall in wake of the
storm early Sunday. WPC probabilities depict low-to-moderate
chances (30-50%) for snowfall totals >8" here with localized totals
approaching a foot a possibility.

...Interior Northeast... Day 3...

The storm responsible for heavy snow over the northern Great Lakes
on Saturday will also generate a hazardous wintry mix from
northern PA on northward into the northern Appalachians. The
Northeast will lay ahead of a strong >750kg/m/s IVT that will
direct copious amounts of moisture northward on Saturday. At the
same time, a cold front will provide just enough cold/dry air at
the surface with Canadian high pressure to the north creating a
weak CAD signature over the Northeast. This healthy 850-700mb WAA
will support a classic overrunning setup of >0C air aloft causing a
mixture of sleet/freezing rain to unfold beginning Saturday
afternoon and continuing into Saturday night. Precipitation may
start out as snow in far northern New England, where wet-bulb
temperatures down the surface may initially support snow. Still,
the concern is for mountains such as the Catskills, Berkshires,
Greens, Adirondacks, and Whites where surface temperatures have
better odds of staying sub-freezing Saturday night and into Sunday morning.

While minor ice accumulations over one-hundreth of an inch are
likely (>70% probabilities) in the Adirondack and Green Mountains,
these ranges also could witness ice accumulations over one-tenth of
an inch, resulting in greater odds for hazardous travels
conditions Saturday evening that linger into Sunday morning. In
terms of snow, the latest forecast generally calls for minor
accumulations (2-4" of snow) over northern Maine, but localized
totals over 6" are possible. WPC's WSSI-P shows >50% chances for
Minor Impacts over the Adirondacks, the Green and White Mountains,
and through much of northern Maine late Saturday into early Sunday.

Mullinax
$$
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FOUS11 KWBC 090819
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
319 AM EST Fri Jan 9 2026

Valid 12Z Fri Jan 09 2026 - 12Z Mon Jan 12 2026

...Upper Midwest & Upper Great Lakes... Day 1...

A swath of heavy/wet snow is ongoing along the western flank of a
storm system racing northeast through the Great Lakes. Snow bands
co-located beneath a classic 250mb jet coupling setup is
maximizing divergence atop the atmosphere at the same time
850-700mb FGEN support intense vertical velocities into a well
saturated DGZ. Boundary layer temperatures are marginally cold,
relaying heavily on the robust vertical velocities aloft and heavy
snowfall rates to keep the depth of the atmospheric column below
freezing. WPC's HREF Snowband Probability Tracker show the
potential for 1"/hr snowfall rates early this morning over
northern WI and the central MI U.P. that includes the Huron
Mountains. The latest forecast calls for 1-3" of snow over north-
central WI and into the heart of MI's U.P.. The Huron Mountains
have the best chances to see 4-6" of snowfall with localized totals
over 6" possible. WPC's WSSI shows largely Minor Impacts in these
areas, although localized Moderate Impacts (hazardous travel
conditions) are forecast around Marquette this morning. Snow tapers
off by midday as the storm races into southeast Canada.

...Central/Southern Rockies & Adjacent High Plains... Day 1...

A vigorous upper level trough over the Four Corners region will
close off into a 500mb low this morning. This system will escort a
plume of Pacific moisture into the Rockies and central High
Plains. Subsequent PVA aloft and favorable jet streak dynamics will
work in tandem with easterly upsloping low-level winds to produce
heavy snow from the Palmer Divide and Sangre De Cristo to the Raton
Mesa and High Plains.

A closed 700mb low will develop over northern NM that gives rise
to a surface low forming in lee of the Sangre De Cristo mountains.
Snow levels will quickly fall below 5000ft by Friday morning, then
as the FGEN banding ensues over southwest KS, the OK Panhandle, and
the northern most counties of the TX Panhandle, snow levels will
fall to as low as 2,000ft during the day. Low-level easterly winds
over the central High Plains favors upslope flow into southern CO
and northern NM peaking early this morning as the 700mb low tracks
just south of Raton Pass. Where the best FGEN forcing sets up and
the strength of the 700mb low will be vital in where the heaviest
snowfall occurs and how far east away from the Raton Mesa and Front
Range the band of heavy snow can advance. Beneath the 700mb FGEN,

1"/hr snowfall rates are expected. The latest HREF and WPC

Snowband Probability Tracker depicts this well with 1"/hr snowfall
rates possible anywhere between the Sangre De Cristo and Raton Mesa
to the TX/OK Panhandles and southwest KS. As the 700mb low moves
northeast Friday afternoon, it will weaken and open up into a
progressive 500mb shortwave, resulting in frontolysis over the High
Plains that diminishes precipitation rates and weakens dynamic
cooling aloft.

Recent 12-24 hour trends have been snowier in the High Plains as
far east as southwest KS thanks to the 700mb low remaining in tact
longer as it tracks east. The latest snowfall forecast calls for
anywhere from 6-12" of snow from the Front Range as far north as
Pikes Peak on south along the Sangre De Cristo and into Raton Mesa.
Given the recent trends for heavier snowfall protruding as far east
as southwest KS, snowfall totals of 4-8" (localized totals >8")
are likely in southeast CO, southwest KS, the OK Panhandle, and the
far northwest reaches of the TX Panhandle. The WSSI is showing a
larger swath of Moderate Impacts in these aforementioned areas
with localized Major Impacts highlighted along the Raton Mesa and
very close to I-25's Raton Pass.

...Great Lakes into the Northeast... Days 2-3...

The shortwave trough responsible for the heavy snow in the the
southern and central Rockies/High Plains tracks eastward into the
MS Valley Saturday night. Farther north, a closed 500mb low in
southern Canada plunges into the Upper Midwest and Great Lakes. As
low pressure deepens over Lake Huron Saturday night, a deformation
zone of snow will envelope the northern Great Lakes. The focus for
heavy snow will be beneath the developing TROWAL that looks to
setup over the U.P. of Michigan. Over the past 24 hours, guidance
has trended more progressive with the storm system and its
associated TROWAL, which has continued the trend of gradually
decreasing snowfall totals. Latest WPC probabilities still show
moderate to high chances (50-75%) for snowfall amounts >4" in the
Porcupine and Huron Mountains of Michigan's U.P., as well as the
norther tier of Michigan's L.P.. Most odds for >6" of snowfall
remain in the 30-50% range, but the Huron Mountains and the tip of
Michigan's Mitten would be most favored for localized snowfall
totals over 8" given additional lake-enhanced snowfall there.

The same storm responsible for the snow over the northern Great
Lakes Saturday night into Sunday will also produce a hazardous
wintry mix across the interior Northeast and heavy snow in northern
New England. A strong >750kg/m/s IVT will direct copious amounts
of moisture northward Saturday into Saturday night. At the same
time, a cold front will inject just enough cold/dry air at the
surface with Canadian high pressure to the north creating a weak
CAD signature over the Northeast. This healthy 850-700mb WAA will
support a classic overrunning setup of >0C air aloft causing a
mixture of sleet/freezing rain to unfold beginning Saturday
afternoon and continuing into Saturday night/early Sunday morning.
Guidance has trended weaker with the primary low over southeast
Canada Saturday night, and with a developing secondary coastal low
near southern New England, the expectation is for sub-freezing
surface temperatures to persist longer. One potential issue for
snow in northern New England is the potential for a 700-300mb dry
slot that could sap moisture in the DGZ aloft over northern NY and
northern VT/NH.

Still, whether it is ice or snow, many of the interior mountain
ranges such as the Catskills, Berkshires, Greens, Adirondacks, and
Whites are favored to see the heaviest wintry precipitation Saturday
night and into Sunday. As the coastal low takes over on Sunday,
lake-effect snow showers are likely to continue down wind of Lakes
Erie and Ontario while northern Maine would be more likely to see
periods of heavy snow. WPC probabilities indicate moderate chances
(40-70%) for minor ice accumulations over one- hundreth of an inch
across the Berkshires, Greens, Adirondacks, and Whites, with low
chances (10-30%) for ice greater than a tenth of an inch in the
Adirondacks. Regarding snowfall, WPC probabilities for >4" are
moderate (40-70%) over the White Mountains and northern Maine.
Northern Maine has the best chances for witnessing locally heavy
snowfall with low chance probabilities (10-30%) for snowfall totals

8". With lake enhanced snowfall possible in wake of a cold

frontal passage on Sunday, the Tug Hill and Chautauqua Ridge are
sporting moderate-to-high chances (50-80%) for localized snowfall
totals >4" through Sunday night.

Mullinax
$$
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FOUS11 KWBC 100814
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
314 AM EST Sat Jan 10 2026

Valid 12Z Sat Jan 10 2026 - 12Z Tue Jan 13 2026

...Great Lakes... Days 1-3...

An upper-level low over northern MN this morning will project
healthy PVA over the Great Lakes, as well as strong 700mb Q-vector
convergence over northern MI and MI's Upper Peninsula (U.P.). A
plume of 700-300mb moisture wrapping around the northern flank of
the 700mb low will coincide within a TROWAL that focuses a band of moderate-to-heavy snow over the northern Great Lakes. The storm
system will progress east into southern Ontario by Sunday morning
and snow will begin to taper off by late Sunday morning. Most
guidance shows anywhere from 4-8" of snowfall as far west as the
Porcupine Mountains of MI's western U.P. to the Hurons in the heart
of the U.P. and much of the eastern U.P.. Farther south, the
northern-most locations of Michigan's Mitten are forecast to
receive 4-8" of snowfall as well, with localized totals topping 10"
possible where lake-enhanced snow bands stick around longest. Snow
fall totals of 1-4" are also anticipated along the coast of WI and
the western most counties of MI. The WSSI shows Minor Impacts
across all these regions, suggesting residents are likely to
contend with hazardous travel conditions Saturday night and into
Sunday morning.

In wake of this storm system, two more Canadian clipper systems
will race towards the Great Lakes. The first brings light snowfall
to northern MN Sunday afternoon and then into the northern Great
Lakes Sunday night. It is moisture starved and progressive, so
totals will generally range between a coating-3". As that upper-
level shortwave trough heads for the Northeast on Monday, another
clipper over the Canadian Prairies will track into the Upper
Midwest Monday night. This system has a little more moisture to
work with, but boundary layer temperatures are milder and may
result in more of a snow/rain mix on Tuesday. Both wintry setups
will be closely monitored, but snowfall totals are likely to
produce minor snowfall totals rather than highly impactful amounts
at this time.

...Northeast, Ohio Valley, & Central Appalachians... Days 1-3...

On the eastern flank of the approaching Great Lakes storm system, a
strong IVT topping 750 kg/m/s and an advancing 925-700mb WAA will
provide rich moisture and strong low-level forcing to produce
periods of snow and a wintry mix over the interior Northeast.
Freezing rain will be most common today in northern PA, the
Poconos, Catskills, Adirondacks, Berkshires, and Green Mountains.
Latest WPC probabilities show moderate chancres (40-60%) for ice
accumulations over one-tenth of an inch in the Adirondacks, Greens,
and Berkshires, whereas the rest of the listed areas are generally
expected to witness ice accumulations less than one-tenth. Farther
north, snow will be the more common precipitation type from the
northern Adirondacks and White Mountains through northern Maine.
This is due to their locations farther north of the storm track of
the primary low in Ontario, and their placement north of a
secondary coastal low in the Gulf of Maine. The coastal low will
deepen southwest of Nova Scotia on Sunday and support a
deformation zone of heavy snow over northern Maine through Sunday
night. Snow should finally taper off by Monday morning, although
some blowing snow may still be ongoing across Maine. WPC
probabilities show high chances (>70%) for snowfall totals >6" in
northern Maine with low chances (10-30%) for some localized areas
near Caribou that could receive as much as a foot of snow.

This storm system over the Great Lakes will also be responsible for
other winter related hazards over the Ohio Valley and central
Appalachians. Ahead of an approaching 500mb vort max, a sharp low-
level cold front and healthy PVA aloft will support the development
of snow squalls Saturday afternoon as far west as Iowa that race
east towards northern IL and IN Saturday evening. Snow squalls will
race east through the OH Valley Saturday night and reach the Upper
OH Valley and central Appalachians by early Sunday morning. Light
accumulations of a coating to 1" are possible, but the concern is
rapid reductions in visibilities due to a combination of heavy snow
rates and gusty winds. Surface temperatures will also plummet below
freezing and could support quickly accumulating snowfall on roads.
Motorists should ensure they have a way to receive alerts for snow
squall warnings should they be issued.

Meanwhile, as the aforementioned cold front and snow squalls reach
the central Appalachians Sunday morning, upslope NWrly flow will
foster heavy mountains snow in the Potomac and Laurel Highlands
Sunday and into Sunday night. WPC probabilities show moderate-to-
high chances for snowfall totals >2", but there is a lower chance
scenario (10-30%) where the peaks of the Appalachians in eastern WV
and western MD receive as much as 4-6" of snow. Lastly, westerly
flow off Lakes Erie and Ontario will trigger lake effect snow bands
over the Chautauqua Ridge and over the Tug Hill Plateau Sunday and
into Sunday night. WPC probabilities depict moderate-to-high
chances for snowfall >4" through Sunday night. There will be
another chance for additional light snow over the Adirondacks and
Whites on Monday, but aside from the Tug Hill, snowfall will
generally be between a coating to 2" through early Tuesday morning.

Mullinax
$$
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