Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
357 AM EDT Mon May 09 2022

Valid 12Z Mon May 09 2022 - 12Z Thu May 12 2022

...Pacific Northwest to Northern Rockies...

Days 1-2...

Anomalously deep troughing over the Pacific Northwest will
continue over the next few days with the next shortwave trough
currently off the Pacific NW coast pivoting across northern CA
this evening and overnight, before closing off a slow-moving 500
mb low that will drop slowly across central CA Tuesday night, then
pivot over southern CA-NV on Wednesday. This will keep 500 mb
height anomalies between -2 and -3 sigma along with much below
normal 850 mb temperatures (around 2 sigma below normal). Snow
levels as low as 2.5-3 kft will help bring higher snowfall
accumulations to the mountain areas, particularly for the Sierra,
eastern OR, central ID, and across portions of the Northern
Rockies. WPC probabilities for at least 4 inches of snow are
moderate to high (40-80%) on day 1 (12Z Mon - 12Z Tue) across the
northern Sierra as well as the Sawtooth, Salmon River, and
northern Teton ranges. Lighter snowfall lingers into the day 2
period but with rising heights and less moisture available, the
coverage of snow is expected to diminish considerably into day 3.

For days 1-3, the probability of significant icing is less than 10
percent.

Hurley