Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
350 AM EDT Sun Oct 11 2020

Valid 12Z Sun Oct 11 2020 - 12Z Wed Oct 14 2020

Days 1-3...

...Pacific Northwest to the Northern Rockies...
An upper level trough will continue to amplify as it pushes east
of the Continental Divide later Sunday. In the wake of this
trough, strong and deep zonal flow will persist across the
northwest CONUS into midweek, with periodic jet streaks/shortwave
perturbations traversing the region from northwest-southeast late
Sunday into Monday, and again Tuesday-Tuesday night. This will
lead to two additional waves of precip with mountain snows through
Tuesday night.

Snow levels under 6,000 ft will push east of the Divide on Monday
with the ensuing flat upper ridging and WAA, however through
midweek will oscillate a bit north and south of I-90 ahead of and
following the upper shortwaves. Heaviest snowfall Sunday-Sunday
night from the initial shortwave will be from the WA Cascades into
the Bitterroot Range and northern Rockies of eastern ID and
western MT, along with the Tetons, Sawtooth, and Wind River
mountains in northwest WY. Probabilities of at least 6 inches in
24 hrs are highest over these higher ranges -- exceeding 50% over
the highest peaks. By day 3 (12Z Tue-12Z Wed), 24hr probs of 6+
inches will be confined to the northern WA Cascades and far
northern Rockies in northwest MT.


The probability of significant icing is less than 10 percent.

Hurley