Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
331 AM EDT Sun May 01 2022

Valid 12Z Sun May 01 2022 - 12Z Wed May 04 2022

...Pacific Northwest to the Central Plains...
Days 1-3...

A closed mid-level low and its associated frontal system will
weaken a bit through the Great Basin today and across the Colorado
Rockies tonight. Several inches of snow are likely over the Uintas
and Wind River Range at elevations above 8000ft. On Day 2, system
will move onto the Plains but will spread at least some snow
across western and central Nebraska as marginally cold air in the
deformation zone supports a rain to snow changeover where rates
are sufficient. Some models continue to be more aggressive than
others with snow and snow accumulation, which will be fighting
against daytime sun angle. WPC probabilities for at least 4 inches
of snow remain less than 10 percent, but this may be underdone as
some of the 00Z CAM guidance is now quite bullish, too. Question
will be how much can actually stick to the ground.

Farther west, another closed low is forecast to move across the
Pacific Northwest on Monday, with high elevation snow to
especially the Oregon Cascades and the Blue Mountains, then across
the central Idaho ranges. More than 6 inches are likely for the
higher elevations of these areas, mainly above 8000ft. By Day 3,
the upper low will move into the central Rockies with the 700mb
low traveling through Idaho into northwestern Wyoming. From the
Bitterroots to the Big Belts and Absaroka Range, modest snow is
possible with WPC probabilities for at least 6 inches >40% between
days 2 and 3.

For days 1-3, the probability of significant icing is less than 10
percent.

Fracasso