Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
430 PM EDT Sat Oct 29 2022

Valid 00Z Sun Oct 30 2022 - 00Z Wed Nov 02 2022

...Pacific Northwest...
Days 1-3...

Troughing over the Gulf of Alaska will slowly translate
southeastward across the Western US over the next several days.
This will drive the next atmospheric river into NW WA tonight on a
150kt jet streak into British Columbia. The associated surge of
moisture will have PW anomalies +1.5 to +2 sigma and IVT of ~300
to 700 kg/m-s which will result in multi-inch QPF to the Olympic
Peninsula and the central/northern WA Cascades through Sunday
night. Snow levels rise in this warm air to around 7000ft,
confining heavy snow totals to the highest peaks of the northern
WA Cascades where accumulations over 6-12 inches are likely
through 12Z Tuesday (much of the snowfall on Monday).

By late Monday into Tuesday, the AR will weaken and shift
southeastward through Oregon as colder air moves in behind the
front with moderate probabilities for 4 or more inches across the
Cascades to the northern Rockies for Day 3.

Behind the front/under the trough, lower snow levels to below
3000ft from NW to SE across the Pacific Northwest as light
precipitation persists in onshore flow.

The probability of significant icing greater than 0.25" is less
than 10 percent.

Jackson