Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
357 AM EDT Thu Oct 28 2021

Valid 12Z Thu Oct 28 2021 - 12Z Sun Oct 31 2021

...Washington State and the Northern Rockies...
Days 1-3...

Strong, moisture-laden, onshore flow has allowed the return of
heavy precipitation to WA. Snow levels climb to 9000 ft early this
morning limiting heavy snow to the highest Cascades. A cold front
crossing tonight will bring lower snow levels down to around
5000ft, but quickly cuts off heavy precipitation by Friday. 

As the cold front pushes east of the northern Rockies Friday night
into Saturday, post-frontal upslope flow enhanced by a wave
developing over the High Plains will support the potential for
heavy snows along the Lewis Range/Glacier National Park in
northwestern Montana where snow levels are expected to drop to
3000 ft Friday night. Day 2 WPC probabilities for snow
accumulations of 6 inches or more increase to 40 to 60 percent
around Glacier NP. A brief snow burst is likely over the Bighorn
Mountains above about 6000ft Saturday as post frontal flow is
enhanced on the prominent range.


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

Jackson