FOUS11 KWBC 240721
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
321 AM EDT Fri Apr 24 2026

Valid 12Z Fri Apr 24 2026 - 12Z Mon Apr 27 2026

...Northern Rockies & Northern High Plains... Day 1...

Cyclonic flow around the large closed upper-low will continue to
keep snow showers (and some snow squalls) in the forecast across
northern MT and far northwest ND today. Residual 700-300mb layer
moisture combined with easterly upslope flow will also support
additional mountain snow from the Bitterroots and Lewis Range on
south into the Absaroka, Tetons, Wind River, and Big Horn ranges.
Snow will gradually taper off this evening and remain light across
the Northern Rockies through early Saturday morning. WPC
probabilities show moderate-to-high chances (50-70%) for additional
snowfall totals >4" in the mountain rages of central MT, the Big
Horns, and the peaks of the WY Tetons. Additional light
accumulations of a coating-2" are likely along the MT/Canada
border. There are also low-to-moderate chanceS (20-40%) for
snowfall amounts >4" in the peaks of the Black Hills through Friday night.

...Sierra Nevada to the Southern & Central Rockies... Days 2-3...

A 500mb shortwave trough rotating around the southern flank of a
500mb low off the CA coast will track into the Southwest U.S. on
Saturday. Healthy PVA over the Rockies and the left-exit region of
a 250mb jet streak positioned overhead will foster excellent
upper-level divergence while a healthy slug of 700-300mb moisture
arrives from the subtropical Pacific. Temperatures aloft are not
overly cold, so snowfall will be confined to the higher elevations
of the Sierra Nevada on east across the Intermountain West. Snow levels
around 7000ft on the Sierra Nevada at onset Saturday afternoon drop
to around 6000ft Saturday night before tapering off.

48-hour WPC probabilities show moderate-to-high chances (50-80%)
for snowfall totals >8" in the Uinta and San Juans, with similar
odds for >4" of snow in the southern Sierra Nevada. Some of the
more remote peaks of the Sierra Nevada could see close to 10" of
snow, while the remote reaches of the Uinta and San Juans receive a
much-needed 12" of snowfall. Farther north, the Wind River, Tetons,
WY Absaroka, and Big Horns are likely to receive at least another
4" of snowfall on top of the snow they measured from the Thurs-Fri
storm system.

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

Mullinax
$$
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