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FOUS11 KWBC 032015
QPFHSD

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

Valid 00Z Thu Dec 04 2025 - 00Z Sun Dec 07 2025


...Southern/Central Rockies...
Day 1...

The sharp, positively-titled trough currently over the Four
Corners states will continue to translate eastward tonight before
ejecting into the central/southern Plains on Thursday. 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. Meanwhile, Canadian high
pressure dropping into the Plains will result in impressive upslope
flow as cold N/NE winds develop in response. 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 be favorable to support heavy snow. This will
especially be the case above 4000-5000 ft, with snow levels falling
in conjunction with waning snowfall intensity later tonight into
Thursday morning. The latest WPC probabilities continue to show
moderate to high chances (40-80%) for additional accumulations of
>6 inches across portions of the southern San Juans and Sangre de
Cristo mountain ranges, with low to moderate chances (20-50%) of >8
inches.


...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, multiple rounds of snowfall, sometimes
heavy, are expected through the period.

The first event will be associated with an arctic cold front
dragging southeast beneath a shortwave aloft. This front will move
rapidly across the eastern Great Lakes tonight, and then across the
Northeast on Thursday. Along and ahead of this front, the
environment continues to suggest an increasing threat for snow
squalls, especially across Upstate NY and New England on Thursday.
With 0-2km fgen maximizing along the front into elevated RH and
SBCAPE as high as 300 J/kg, widespread linear squalls are likely.
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 afternoon and evening. As a
result, WPC has initiated Key Messages to highlight this event. See
the link below for more details.

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 between -15C to -20C Thursday, and
then between -10C to -15C late Friday into Saturday, 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 2...

Plenty of uncertainty heading into Day 2 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/QPF fields from the various global ensembles the past few
runs, with the ECMWF and various machine learning suites the
farthest north. While it still remains too early to iron out the
details, WPC probabilities of 1+ inches of snow across the Central
Appalachians and into eastern VA/MD have increased to 20-60%, with
the highest chances in the higher terrain of WV/VA. WPC
probabilities for 2+ inches are between 10-20% from eastern WV to
central VA.

South of the potential moderate snow, an axis of light
freezing rain is also possible where a p-type transition occurs
underneath a stubborn layer of low-level cold air. The latest WPC
probabilities maintain a 10-30% chance for at least 0.1" of ice
across northern NC and into southern VA.


...Northern to Central Rockies...
Days 1-3...

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 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 Day 2 and 3 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 2 and 3 reach above 70% for 8+ inches, and Day 2
and Day 3 snowfall could be impressive above generally 6000 ft
where locally 1-2 feet is possible.

Miller/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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