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

Valid 12Z Sat Oct 29 2022 - 12Z Tue Nov 01 2022

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

Troughing over the Gulf of Alaska will slowly translate
southeastward into the Pacific Northwest over the next several
days. This will drive the next atmospheric river into NW WA this
evening 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. 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 early Tuesday, the AR will weaken and shift
southeastward through Oregon as colder air moves in behind the
front. This will lower snow levels to below 4000-5000ft from NW to
SE as precipitation lightens over much of the area.

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

Fracasso