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FOUS11 KWBC 022051
QPFHSD

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

Valid 00Z Wed Dec 03 2025 - 00Z Sat Dec 06 2025


...Northeast...
Days 1...

Low pressure now moving north along the Mid Atlantic coast will
deepen rapidly through the evening as the associated shortwave
trough moves through the Northeast/Mid Atlantic, and assumes a
negative tilt as it moves offshore. This system will move quickly
overnight, tracking from near the 40N/70W benchmark at 00Z to east
of Nova Scotia by daybreak. The back edge of the associated
precipitation shield will move quickly to the east as well, with
snowfall ending for most areas apart from coastal northern New
England by tomorrow morning. Additional snowfall accumulations
after 00Z are expected to be light for most areas, with WPC
probabilities indicating the chance for accumulations greater than
4 inches are negligible for most areas, with some 10-30
probabilities confined to coastal Maine and southern New Hampshire.

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

A low amplitude shortwave trough dropping through the Pacific
Northwest today is forecast to amplify as it digs south along the
Sierra Nevada/Great Basin overnight, with the model consensus
showing a well-defined positively-tilted trough dropping into the
Southwest/Four Corners on Wednesday. Meanwhile at the surface, a cold
front will settle south into the southwestern U.S. A low level
circulation developing and dropping south through western Colorado
will help to enhance snowfall over the western Colorado ranges,
notably the San Juans, where WPC guidance shows some isolated
higher probabilities for accumulations greater than 6 inches on Day
1. More widespread higher amounts are expected to develop along
the eastern ranges from the Front Range south to the northern
Sangre de Cristos - supported by increasing upslope flow on the
backside of a sharp ridge nosing south along the High Plains.

From Wednesday night into early Thursday, the shortwave over the
Southwest will begin to eject east, focusing snow further south
over the Rockies. Amounts are expected to me mostly light, with WPC
probabilities indicating amounts over 6 inches will remain mostly
confined to the higher peaks of the southern Sangre de Cristos.


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

An arctic front associated with an amplifying trough over eastern
Canada will sweep across the upper Great Lakes on Wednesday,
setting off a period of lake effect snow showers that will continue
into early Thursday before a shortwave ridge moves over the region.
Overall, accumulations for the two-day period are expected to be
generally light. Although some parts of the eastern U.P. are likely
to see totals over 4 inches.

Meanwhile, the previously noted front will advance east of the
lakes, moving across the Northeast on Thursday. While heavy
accumulations along the front are not expected, snow squalls remain
a concern, with the NAM continuing to show some notable Snow
Squall Parameter values as the front advances across Upstate New
York and New England. This indicates a brief period of intense
snowfall that is likely to reduce visibilities and impact travel.
Behind the front, lake effect snow showers will develop briefly off
of lakes Erie and Ontario Wednesday night into Thursday, with the
best chance for heavy accumulations centered over the Tug Hill
region.

The aforementioned shortwave ridging is forecast to develop ahead
of another shortwave that is expected to dive southeast across
central Canada on Thursday and amplify as it brushes the upper
Great Lakes Friday morning. Most of the better forcing and lake
enhancement is expected to remain north of the lakes; however some
lighter amounts are likely, especially over northern Michigan.


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

The previously noted shortwave over the Southwest will move east of
the southern Rockies on Thursday, becoming less amplified as it
moves into a region of confluent upper flow. However it will
provide enough lift to spread some light precipitation north into
the Mid South/Tennessee Valley, with a low end chance for some
light wintry precipitation/ice accumulations Thursday night into
early Friday. A greater chance for light snow/ice accumulations is
expected to develop farther east over the southern Appalachians,
where a cold air wedge is forecast to linger long enough to support
at least some minor accumulations on Friday.

...Northern Rockies...
Day 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.
Favorable mid to upper level forcing along with a notable influx of
Pacific moisture will be sufficient for some heavy totals over the
northern Rockies from northern Idaho and western Montana to
western Wyoming -- where WPC probabilities indicate widespread
totals over 4 inches are likely, with amounts over 8 inches
possible in the higher terrain.

Pereira

...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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