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FOUS11 KWBC 221911
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
211 PM EST Wed Jan 22 2025

Valid 00Z Thu Jan 23 2025 - 00Z Sun Jan 26 2025

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

A clipper system tracking through Lake Superior today will lead to
modest WAA-driven snow over the region from northwest to southeast
tonight into Thursday. With the in situ air mass still plenty
cold, periods of light snow are expected with the passage of the
system with some lake enhancement as well. Cyclonic flow will
persist in the wake of the weakening clipper system which may
trigger a few lake snow bands off Lakes Superior and Michigan
tomorrow then off Lakes Erie/Ontario tomorrow night before snow
winds down. Lastly, another fast-moving clipper should brush
through the region D3 (Sat) with another round of light snow but
perhaps some modest amounts over the Keweenaw Peninsula. WPC
probabilities for at least 8 inches of the 3-day period are highest
(>30%) over the Keweenaw, western Lower Michigan, and southeast of
Lake Ontario.


...The West...
Days 1-3...

Upper ridge axis just off the West Coast will reorient itself
westward, allowing height falls to sink through the near-interior
West Fri/Sat. Lead/weaker height falls on the southwest side of a
trough axis out of central Canada tomorrow will bring some light
snow to the northern Rockies with amounts generally 1-4". For days
2-3, height falls combined with a modest 120-kt jet moving through
MT will promote broad lift over the northern Rockies (Fri),
especially western MT into northwestern WY, with some local
enhancement/upslope. By D3 (Sat), the jet will increase over the
central Plains, favoring additional lift over the central Rockies
(southern WY into CO) with continued local upslope on easterly flow
as high pressure noses down the western High Plains. Core of the
height falls will be farther west over NorCal/Great Basin but
moisture will be a bit lacking. Generally light snow is expected
over the northern/central Sierra and across northern NV/UT, though
this may increase toward the end of the period as the trough
sharpens and may close off into a closed low over NorCal late Sat.

WPC probabilities of at least 8 inches of snow over the next three
days are highest (>50%) over central Montana and northern Wyoming
(Little Belt, Big Snowy, Absaroka, and Big Horns) as well as into
the CO Rockies and southern WY (Medicine Bow and Park Range).


For the days 1-3 period, the probability of significant icing
greater than 0.10" is less than 10 percent.


Fracasso


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

https://www.wpc.ncep.noaa.gov/key_messages/LatestKeyMessage_2.png

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