Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
430 PM EDT Sat Apr 30 2022

Valid 00Z Sun May 1 2022 - 00Z Wed May 4 2022

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

A closed mid-level low and its associated frontal system is making
its way inland across the Pacific Northwest Saturday afternoon,
and will continue tracking southeast towards the Colorado Rockies
by Monday morning.  Except for the highest terrain of the
Olympics, Cascades, Blues, and central Idaho ranges, no
significant snow accumulations are expected.  The best prospects
for several inches of snow will be confined to the Uintas and Wind
River Range. 

As this system emerges over the central High Plains, there is
still some model uncertainty on the exact surface system evolution
off the Front Range.  The latest runs of the NAM and GFS still
support the idea of rain changing to snow during the day Monday
over the Nebraska Panhandle and potentially across central
portions of the state as well.  Though the conditions in the
deformation band to the northwest of the low-mid level circulation
may support enough cooling of the column to support an eventual
change to wet snow, timing would be during the day and the higher
sun angle this time of year will tend to mitigate accumulation
potential.  WPC probabilities for at least 4 inches of snow remain
less than 10 percent here, but 1-3 inches of snow could accumulate
during periods of enhanced snowfall rates if they develop.

Another closed low is forecast to move across the Pacific
Northwest on Monday, with high elevation snow to the Oregon
Cascades and again to the Blue Mountains and central Idaho ranges
as it moves towards the northern Rockies by early Tuesday.  Some
potential exists for 6-10 inches for portions of central Idaho and
southwest Montana, mainly above 8000 feet elevation.

The probability of significant icing is less than 10 percent
nationwide.

Pereira/Hamrick