Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
249 PM EDT Fri Sep 30 2022

Valid 00Z Sat Oct 01 2022 - 00Z Tue Oct 04 2022

...North-Central Rockies...

Days 1-2...

500mb low will amplify and drop SE into NW WY tonight and Saturday
before pivoting slowly off to the northeast Sunday into Monday.
Paired downstream divergence with upper level diffluence will
combine with moist 700mb upslope flow to drive deep layer ascent
into the terrain, most notably during D1 before the primary PV
anomaly swings to the east the latter half of the weekend.
Moisture will increase both from the Gulf of Mexico, and more
impressively from a plume of higher PWs near the Gulf of
California to provide an environment that above 9000 ft will
support periods of moderate to heavy snow. The model SLRs continue
to appear too high for this event based on soundings and time of
year, so have lowered them below the NBM for this update. Still,
this results in a 20-30% chance for 8" of snow in the highest
terrain of the Wind Rivers and Absarokas, most of which is
expected on D1.

For days 1-3, no icing is forecast.

Weiss