Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
336 AM EST Fri Nov 20 2020

Valid 12Z Fri Nov 20 2020 - 12Z Mon Nov 23 2020


...Pacific Northwest/Northern Rockies...
A shortwave trough sliding southeast across British Columbia into
the northern U.S. Rockies will support additional showers,
including mountain snows, from western Washington to northern
Idaho and northwestern Montana.  Snow amounts will be relatively
light, with most areas seeing only a few inches of additional
accumulation at most.  A shortwave ridge will bring dry conditions
across the region on Saturday before wet weather returns on
Sunday.  An upper level shortwave trough and its associated
frontal system will likely bring light snows back into the
Olympics and Cascades by midday.

For Days 1-3, the probability of significant icing (0.25-inch or
more) is less than 10 percent.

Pereira