Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
303 AM EDT Thu May 1 2025

Valid 12Z Thu May 01 2025 - 12Z Sun May 04 2025


...Sierra Nevada...
Day 3...

A potent closed low will dig along the CA coast Saturday into
Sunday, with rapid amplification of this feature expected by Sunday
morning. This is reflected by NAEFS height anomalies falling to
below the 1st percentile with respect to 700-500mb heights over
southern CA by 12Z Sunday. Although the accompanying jet streak
will intensify as well as it pivots around the upstream side of
this trough and through the base, the overall evolution will keep
the most intense ascent displaced south/east of the Sierra, but
sufficient lift and increasing moisture will still result in
periods of snowfall D3. Snow levels during this time will begin
around 8000-9000 ft, so only the higher Sierra Passes will begin as
snow, but as the upper low digs across CA, snow levels are progged
to fall to as low as 7000 ft, bringing at least some accumulations
to Donner Pass as well. Overall, significant snowfall accumulation
will be confined to above pass level, where WPC probabilities for
more than 6 inches of snow are as high as 50%, but light snow down
to most Sierra Pass levels is also likely before precip winds down
by Sunday morning.


The probability of significant freezing rain across the CONUS is
less than 10%.

Weiss