Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
428 PM EDT Sat Sep 30 2023

Valid 00Z Sun Oct 1 2023 - 00Z Wed Oct 4 2023

...Sierra Nevada through the Northern Rockies...
Days 1-3...

An amplifying mid-level shortwave trough currently over central
California will evolve into a closed low over north-central Nevada
by Sunday morning, and then meander in place through Monday across
eastern Nevada/western Utah before opening up into an open wave by
Monday night.  In terms of winter weather potential, snow showers
should taper off across the Sierra by Sunday morning, with total
accumulations on the order of 4 to 8 inches expected along the
higher ridges, generally above tree line.  There may be some
lingering snow showers going into Sunday as well with some
instability associated with the upper low nearby in combination
with some northeasterly flow from the developing surface low.

Attention then turns to the highest mountain ranges of the
Intermountain West going into Sunday and early Monday as the upper
low/trough reaches northeastern Nevada and northwestern Utah.  It
appears the Uinta Mountains will likely get the greatest snowfall
totals for this time period, with 6-12 inch accumulations likely
here above 9000 feet where the 700mb flow is oriented more
orthogonal to the terrain.  There has been an upward trend in the
model guidance with expected snowfall here compared to yesterday. 
Several inches of snow is also likely for the highest ridges of
the Wasatch, Wind River, Absaroka, and Big Horn Mountains.


The probability of any ice accumulation across the Continental
U.S. is less than 10 percent.

Hamrick