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FOUS11 KWBC 152028
QPFHSD

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

Valid 00Z Tue Dec 16 2025 - 00Z Fri Dec 19 2025


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

Warm advection around the northern periphery of a bubble of high
pressure centered over the Southeast U.S. will result in the
development of a single lake effect snow band off Lake Ontario this
evening, focused into the Tug Hill Plateau through the night
before tapering off Tuesday morning. Model soundings depict strong
and saturated lift within a deep DGZ, supporting moderate to heavy
snow across the Tug Hill. As a result, WPC probabilities are
moderate (40-60%) for snow accumulations >8", and high (>70%) for
accumulations >6".


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

After a shortwave trough brings a cold front through this evening,
which will lower snow levels amid lighter QPF to around 4000ft in
WA and 5000ft in northern OR, snow levels are progged to 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. Low snow levels and precip rates persist then
through Wednesday night before another push of moisture and
mountain snow move in during the day on Thursday. The latest WPC
probabilities remains high for snowfall accumulations >8"
(particularly for the Washington Cascades) each day from 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 Tuesday night into Wednesday, followed by another
surge on Thursday, with falling snow levels. The latest WPC
probabilities for snowfall >8" are moderate to high (40-80%) for
the highest elevations of northern ID and western MT Day 1,
increasing to high (>70%) for a larger footprint of ranges across
ID, western MT, and western WY Day 2. Probabilities of >8" then
drop back to 30-70% for Day 3, with most confined to ID and WY.


...Northern Plains and Upper Midwest...
Day 3...

A strong area of low pressure (minimum MSLP currently modeled
outside of climatology) progged to track eastward along the
U.S./Canada border roughly from Montana to the Upper Great Lakes
will support a swath of moderate to heavy snowfall within the
deformation zone / cold comma head across portions of the northern
Plains and Upper Midwest later Wednesday night into Thursday.
Relatively fast forward speed should put a cap on the overall
potential from an accumulation standpoint, but even so, the latest
WPC probabilities for snowfall >4" are moderate to high (40-70%)
across northeast ND and northern Minnesota, with odds of 10-30% for
>8". Regardless of snow accumulations, impacts could be more
notable than typical as a result of a very tight pressure gradient
and the potential for blowing and drifting snow due to strong gusty
winds.


The probability of significant icing is less than 10 percent.

Miller/Jackson


$$