Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
252 AM EDT Wed Oct 20 2021

Valid 12Z Wed Oct 20 2021 - 12Z Sat Oct 23 2021


...Pacific Northwest and Northern California...
Days 1-3...
A wet pattern will commence, with a pair of upper level shortwaves
and their associated frontal bands impacting the region over the
next three days.  The initial system will move onshore this
morning.  Snow levels this morning are expected to be above 5000
ft along much of the Cascades and above 8000 ft in the northern
Sierra Nevada -- confining any significant snow impacts to the
higher peaks. 

Snow levels are expected to climb higher ahead of the next system
as it approaches the coast late Thursday.  Snow levels above 8000
ft in most places late Thursday are expected to drop overnight
through Friday as this system moves inland.  As snow levels drop
back down to 6000 ft, isolated heavy snow accumulations are
possible for portions of the Olympics, Cascades, the northern
Sierra Nevada, and the Wallowa Mountains.   

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

Pereira