Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
237 PM EDT Sun May 3 2026

Valid 00Z Mon May 04 2026 - 00Z Thu May 07 2026

...Sierra Nevada...
Days 1-2...

Upper low just offshore NorCal this evening will move inland
through central then southern CA and into AZ late Tuesday as it
weakens into a positively-tilted open wave. A modest plume of
moisture will intersect the Sierra and promote light to locally
modest snow for the higher elevations as snow levels start around
9000ft this afternoon. As the cold core moves inland, snow levels
will drop to around 8000ft. Snow will end by Tuesday evening as
heights begin to rise. WPC probabilities for at least 6 inches of
snow are >50% above about 8500-9500ft.


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

Building upper ridging north of the CA upper low will amplify over
the northeast Pacific into NW Canada through Monday, promoting
downstream troughing to surge down the Canadian Prairies tonight
and the northern Plains Monday. Upper jet out of the subtropics
will arc across the Four Corners region and provide modest synoptic
lift over the region with light and mainly high elevation snow in
advance of a strong cold front. Snow levels initially
>9000-10,000ft will crash behind the cold front on Tuesday as it
races southward. Snow levels will lower over eastern CO to
6000-7000ft behind the boundary that will dam up 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) with additional modest snow over the Bighorns and
Wind River Range through Tuesday evening before tapering off as the
focus shifts east onto the Plains Wednesday. WPC probabilities for
at least 8 inches of snow are >50% above about: 9000-10,000ft over
the Bighorns and Wind River Range, 7000ft from southern WY into
the CO Rockies, and 10,000-11,000ft in the northern Sangre de
Cristos. The highest amounts of snow -- at least 18 inches -- are
most likely above 10,000ft in CO which could cause moderate impacts
to travel via I-70 west of Denver across the Divide.

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


Fracasso