Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
447 AM EDT Sat May 07 2022

Valid 12Z Sat May 07 2022 - 12Z Tue May 10 2022


...Pacific Northwest...
Days 1-3...
A quasi-stationary upper level pattern is expected to develop
across the CONUS this period, with broad cyclonic flow persisting
over the West through early next week.  A series of low-amplitude
shortwaves moving through the broader scale flow will bring
showers and cooler temperatures across the Northwest into the
northern Rockies today.  With snow levels on the decline, WPC
probabilities indicate that accumulations of 4 inches or more are
likely at or below many of the Cascade passes.  Significant
accumulations are also likely farther east across the higher
elevations of the northern and central Idaho to the western
Montana ranges. 

On Sunday, a compact upper low moving into base of the broader
scale trough is expected to bring organized, heavier precipitation
farther south into the southern Cascades and Northwest California
ranges.  With snow levels remaining low, widespread accumulations
of 4 inches or more are likely, with amounts of 8 inches or more
possible across the higher peaks. 

By late Monday and continuing into Tuesday, the threat for heavy
snow is expected to wane as the onshore momentarily wanes across
the northwestern U.S. 

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

Pereira