Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
149 PM EDT Thu Oct 24 2024

Valid 00Z Fri Oct 25 2024 - 00Z Mon Oct 28 2024


...Pacific Northwest...
Day 3...

A moderate atmospheric river characterized by IVT peaking around
400-500 kg/m/s will advect into the Pacific Northwest Sunday. This
will spread ample moisture onshore, resulting in widespread
precipitation moving from the Olympics and Cascades to as far east
as the Northern Rockies by the end of the forecast period. Ascent
will intensify D3 as well as a potent shortwave shedding from a
closed low off the British Columbia coast moves onshore, collocated
with the advance of a Pacific jet streak. Combined, this will
result in heavy precipitation Sunday, especially where upslope flow
enhanced ascent in the Olympics and Cascades. Snow levels will
initially be 7000-8000 ft, but will fall steadily to around
4000-5000 ft by Sunday night, allowing for accumulating snow to
gradually lower through the terrain. Still, the most significant
accumulations will be confined above 5000 ft where WPC
probabilities for more than 4 inches peak as high as 30-50% in the
Cascades, but above 80% on the highest peaks like Mt. Rainier.

The probability of significant ice across the CONUS is less than
10 percent.

Weiss