Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
347 PM EDT Mon May 09 2022

Valid 00Z Tue May 10 2022 - 00Z Fri May 13 2022

***This is the final regularly scheduled Heavy Snow/Ice Discussion
for the 2021-2022 season from WPC***
--This discussion may be updated over the next couple months
should the forecast warrant


...West Coast...
Day 1...

Anomalously deep troughing over the West Coast down through
northern California will persist through Tuesday, May 10 before
shifting east, crossing the northern Rockies by Thursday morning.
A steady onshore flow will maintain light to locally moderate
precip rates over southern OR and northern CA through Tuesday.
Snow levels drop to around 3000ft tonight before rising back to
4000ft through Tuesday. This results in low Day 1 WPC
probabilities for over 6" additional snow for the far southern OR
Cascades, the CA Cascades into the northern Sierra.

...Northern Rockies...
Day 3...

The aforementioned trough crosses the northern Rockies (focus near
the CO/WY border) Wednesday night into Thursday. It will be quite
warm ahead of this trough, so precip ahead of the wave should be
mainly rain (snow levels up around 9000ft Wednesday night).
However, a lee-side surface low tracking up the Dakotas on
Thursday brings precip back over to the northern Rockies with the
snow level dropping to around 7000ft. There are low to moderate
Day 3 snow probabilities for over 6" to the higher reaches of the
major WY Ranges east from 110W; the Absarokas (stretching into
MT), Wind Rivers, and Bighorns.

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

The next low to push into the Pacific Northwest (currently
gathering over the Gulf of Alaska) reaches the WA coast by late
Thursday, May 12. Ample Pacific moisture streams in ahead of the
trough will widespread moderate precip expected on Thursday. Snow
levels will be around 3500ft, so there are moderate Day 3
probabilities for over 6" snow for the Olympics and WA Cascades.


No freezing rain is forecast.

Jackson