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

Valid 00Z Thu Apr 24 2025 - 00Z Sun Apr 27 2025


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

A shortwave moving through the northern Great Basin tonight will
spread generally light snow across central ID, southwestern MT, and
northwestern WY Thursday as it deepens a bit then lifts
northeastward into southwestern Montana tomorrow afternoon. Right
entrance region of a retreating upper jet will promote broad ascent
over the region where temperatures are mostly mild, confining
snowfall to areas above 7000ft or so. Snow will taper off by Friday
morning as the feature weakens over western Montana. WPC
probabilities for at least 8 inches of snow over the next 36 hours
are moderate (40-70%) over the Absarokas and Wind River ranges and
generally less than 50% over the Bighorns.


...Oregon & California...
Days 2.5-3...

A potent upper trough in the northeastern Pacific Thursday will
dig and deepen into a closed low just west of NorCal by Friday,
sending in some moisture to the region as early as Thursday
evening. This upper low is then forecast to move inland over
central CA Saturday morning, with a trend to the south since
yesterday. Snow levels will start high (over 7000ft), but fall to
below 6000ft by early Saturday as the precipitation shield expands
in response to the strengthening upper jet over SoCal. WPC
probabilities for at least 6 inches of snow are low (~10%) for the
Oregon Cascades due to the decrease in QPF, low (10-40%) over the
northern CA ranges, and moderate (40-70%) over the northern/central
Sierra Nevada (generally above 7000ft). Snow is expected to
continue into the day 4 timeframe.


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


Fracasso