Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
323 AM EST Fri Dec 14 2018

Valid 12Z Fri Dec 14 2018 - 12Z Mon Dec 17 2018


...Pacific Northwest to the Northern Rockies...
A potent northern stream trough will push across the Pacific
Northwest (north from northern CA) tonight into Saturday with the
surface low crossing Vancouver Island. The majority of
precipitation will fall this afternoon over the Coast Ranges and
Cascades just ahead of the cold front from this low. Snow
elevations will be 4000-5000ft with high probabilities for four
inches of snow above this level in far northern CA and western
OR/WA.

Shortwave ridging results in light to no precip late tonight
through Saturday. The trough from a deep low over the Gulf of
Alaska brings the next round of precip to the Pac NW late
Saturday. However, tropically sourced moisture will have rather
high snow elevations (6000-7000ft) ahead of the mid-level trough
axis which does not reach the coast until Monday. The greatest
moisture fetch is into far northern CA with the northern CA
Cascades having moderate probabilities for six inches of snow for
Day 3.

Jackson