Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
348 PM EDT Sun May 08 2022

Valid 00Z Mon May 09 2022 - 00Z 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 a compact closed mid-level
low swinging onshore this evening followed by another vort max
later in the day 1 period. 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
2-3 kft will help bring higher snowfall accumulations to the
mountain areas, particularly for the Sierra, eastern OR and across
portions of the Northern Rockies. WPC probabilities for 4 inches
are moderate to high for the Sierra and southwest MT and parts of
the Yellowstone region. 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.

Taylor