Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
459 AM EDT Mon May 4 2026

Valid 12Z Mon May 04 2026 - 12Z Thu May 07 2026

...Sierra Nevada...
Day 1...

Upper low just over SF Bay will drift southeast to southern CA
through Tuesday before opening and ejecting east over AZ Tuesday
night. A modest plume of moisture will intersect the Sierra and
promote light to locally modest snow for the higher elevations as
snow levels remain around 8500ft. Snow will end Tuesday evening as
heights begin to rise. Day 1 WPC snow probabilities for >6" are
>50% above about 8500ft.


...Wyoming and Colorado...
Days 1-3...

Upper ridging continues to build north of the CA upper low and
extends into the Yukon today, promoting downstream troughing to
surge down the northern Plains through this afternoon. WSWly jet
out of the Pacific subtropics will arc across the Four Corners
region today and provide lift over the cold front that enters CO
tonight. Snow levels of 9000 to 10,000ft will crash behind the cold
front on Tuesday as it shifts southward. Snow levels will lower
over eastern CO to 6000-7000ft as the boundary dams up against east
of the Divide, keeping snow levels >8000ft on the west side.
Modest to locally heavier snow should set up over parts of
southern WY through CO via easterly/upslope flow (e.g., Laramie and
Medicine Bow Mountains) as the upper low pushing into central CA
promotes lee-side troughing on the Rockies and some delay to the
cold frontal passage. Precip shifts down the Rockies through
Wednesday
night before shifting east onto the Plains.

Day 1 WPC probabilities for >6" of snow are 40-80% over the
highest Snowy Range in WY and Front Range in CO. Day 2 is the
busiest day with renewed snow in both WY and CO including onto the
High Plains/Denver and snow probs >8" 50-90% over the Front Range
and generally 40-80% for the Wind River, Park Range, Pikes Peak,
and higher portions of the Palmer Divide. Meanwhile snow probs for
>4" are 20-40% over the CO High Plains. Day 3 snow probs highlight
the southward shift in the frontal pattern with 30-50% for >8" snow
in the Sangre de Cristos.


The probability for significant icing over one-tenth of an inch is
less than 10 percent across the CONUS.


Jackson