Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
327 PM EDT Wed May 04 2022

Valid 00Z Thu May 05 2022 - 00Z Sun May 08 2022


...Pacific Northwest...
Days 2-3...

A series of shortwave troughs are expected to move through the
Pacific Northwest over the next several days within the broad
cyclonic flow over the region. The first comes Thursday/Thursday
night but snow levels are quite high such that little if any
snowfall is expected except for the tops of Rainier, Adams, and
St. Helen. In the wake of that system, snow levels fall and then
the second system is poised to arrive later Friday into Saturday
morning. A 130+ kt jet noses into Oregon and with favorable left
exit region dynamics combined with the approach of a surface low
and modest amounts of moisture (PWs +1 to +2 sigma), accumulating
snow is expected for the OR/WA Cascades above 5000 ft. Toward the
end of the Day 3 and beyond, another system approaches with lower
snow levels, expanding the threat of accumulating snow to the
terrain areas of the Cascades as well as the central Idaho ranges
into northwest Montana where WPC probabilities for 4 inches or
more reach moderate to locally high percentages.


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

Taylor