Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
209 PM EST Sat Nov 9 2024

Valid 00Z Sun Nov 10 2024 - 00Z Wed Nov 13 2024

...Western U.S....
Days 2-3...

A potent upper trough currently rounding a deep low over the Gulf
of Alaska will further amplify as it digs south toward the PacNW
coast Sunday night with the base of the trough crossing northern CA
on Monday. This sharp trough then shifts east over the
northern/central Rockies through Tuesday. 

Elevated moisture with a plume of 1-1.25" PW streams into the
Cascades Sunday night ahead of the axis with snow levels generally
6000-7000 ft, before dropping to 4000-5000ft under the trough on
Monday. Moderate precip rates are expected behind the cold front
Monday into Tuesday as moist onshore flow persists, leading to
prolonged snow at and above the higher pass levels in WA/OR
Cascades. Day 2 PWPF for >6" is generally limited to the highest
Cascades, but Day 3 is above 50% at pass level with a couple feet
likely for the highest peaks.

The cold front progresses inland to the northern Rockies Monday
afternoon with a couple rounds of mountain snow (snow levels drop
from around 8000ft to 5000ft with the frontal passage) expected
through Tuesday. Day 3 PWPF for >6" are 40-80% for the Salmon
River, western Sawtooths, Bitterroots, Tetons, and ranges around
Glacier NP.

A band of frontal precip/mountain snow can be expected over
northern CA late Monday with Day 2.5 PWPF 20-60% for >6" for the
Trinity Alps, CA Cascades, and northern Sierra Nevada with snow
levels dropping from 6000ft to 5000ft with the frontal passage.


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

Jackson