Subj : HVYSNOW: Probabilistic Heavy Snow And Icing Discussion
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Sat Feb 04 2023 08:15:03

FOUS11 KWBC 040814
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
314 AM EST Sat Feb 04 2023

Valid 12Z Sat Feb 04 2023 - 12Z Tue Feb 07 2023


....Western U.S....
Days 1-3...

Amplified longwave trough currently over the eastern Pacific will
move onshore California late tonight into early Sunday. Favorable
forcing for ascent aided by the left exit region of a 110-120 kt
jet rounding the base of the upper trough will provide a decent
shot of moderate precipitation beginning Saturday evening through
much of Sunday. PW anomalies associated with this feature are
marginally above normal (+1.5 sigma) and IVT values approach
400-500 kg/m/s across central CA into the Sierra Nevada. The
longwave trough is expected to progress eastward through interior
West late this weekend, reaching the Four Corners region by late
Monday into early Tuesday. This deep layer ascent within an
environment of high moisture will result in heavy snowfall across
much of the western terrain. Snow levels are expected to be
generally 4000-5000 ft, rising higher to near 7000 ft across CA.
For Day 1 (12Z Sat-12Z Sun), this will keep the greatest
accumulations confined to the highest peaks of the Sierra Nevada
where probabilities are high for a foot or more of snow (locally 2
feet possible). Through Days 2-3 (12Z Sun-12Z Tue), a large/broad
area of heavy snow as moisture and lift spread eastward with the
progressing trough axis with the greatest accumulations expected
from OR/WA Cascades, Sierra Nevada eastward through the
Bitterroots of ID, WY Tetons and down in the UT Wasatch. WPC
probabilities for 6" or more of snow reach moderate to locally
high levels for those ranges days 2-3.


The probability of significant icing is less than 10 percent.

Taylor

$$



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