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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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