Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
254 AM EDT Wed Apr 23 2025

Valid 12Z Wed Apr 23 2025 - 12Z Sat Apr 26 2025


...Northern Rockies...
Days 1-2...

Shortwave moving through OR this morning will spread a new round
of generally light snow across southwestern MT and northwestern WY
as it deepens over the northern Great Basin tonight. Upper jet
will be positioned over the northern Plains, aiding in ascent over
the region where temperatures are mostly mild, confining snowfall
to areas above 7000ft or so. This feature will weaken as it pushes
through ID and into western MT Thursday night with snow tapering
off by Friday morning. WPC probabilities for at least 8 inches of
snow are moderate (40-70%) over the Absarokas and Wind River ranges
and generally less than 40% over the Bighorns.


...Oregon & California...
Day 3...

A potent upper trough in the northeastern Pacific will dig and
deepen into a closed low just west of NorCal by Friday, sending in
some moisture to the region. This upper low is then forecast to
begin
moving inland over central CA Friday night, with some lingering
uncertainty regarding exact timing. Snow levels will start high and
around 7000ft, but fall to around 5000ft by 12Z Saturday just as
the precipitation shield becomes more expansive in response to the
strengthening upper jet over SoCal. WPC probabilities on day 3 for
at least 6 inches are low (10-40%) across the southern OR Cascades
into the NorCal ranges and central Sierra Nevada. More snow is
expected into the day 4 timeframe.


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


Snell