Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
314 AM EDT Thu Apr 24 2025

Valid 12Z Thu Apr 24 2025 - 12Z Sun Apr 27 2025


...Northern Rockies...
Day 1...

A shortwave trough over the Great Basin (axis currently over the
NV/ID border) will shift ENE over the Yellowstone region this
evening. Some moist flow ahead of the trough will lift over a
stationary front over southern WY and continue to bring light to
locally moderate mountain snow until the trough crosses this
evening to higher portions of the Absarokas, Wind River, and
Bighorns, where Day 1 probabilities for an additional >4" snow
after 12Z are 10-30%. Snow levels in this mild airmass are
generally 7000ft or higher in northern WY.


...Sierra Nevada...
Days 2/3...

A negatively-tilted upper trough reaches the central CA coast
tonight as an upper low develops offshore and tracks to the central
CA coast through Friday night. This low then drifts to southern NV
through Saturday night. Moisture inflow and topographical lift over
the central Sierra become sufficient for higher elevation snow by
later Friday afternoon with a prolonged light to locally moderate
snowfall then into Sunday. Snow levels begin around 6500ft, but
drop to as low as 5000ft under the upper low. Day 2.5 WPC
probabilities for >6" are 30-50% for the Sierra Nevada generally
above 7000ft in 24hrs (00Z Sat to 00Z Sun).


The probability of at least 0.10" of freezing rain across CONUS is
less than 10%.


Jackson