Probabilistic Heavy Snow and Icing Discussion...amended
NWS Weather Prediction Center College Park MD
605 PM EDT Sun May 1 2022

Valid 00Z Mon May 2 2022 - 00Z Thu May 5 2022

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

The low pressure system currently crossing the Rockies will emerge
over the Plains Monday morning, and will likely result in at least
some snow across western and central portions of Nebraska, and
perhaps into extreme southern South Dakota, as marginally cold air
within the lower troposphere under the deformation zone likely
supports a rain to snow changeover where precipitation rates are
sufficient.  The latest high res guidance, including the 18Z HRRR,
suggests a changeover to wet snow from southeast Wyoming by 12Z,
and then across western Nebraska by 15-18Z as the column cools
further.  Although WPC probabilities for 4+ inches are currently
below 10 percent for this region, there is a good chance for 1 to
2 inch amounts between Cheyenne and Valentine, Nebraska, mainly on
grassy surfaces, by midday Monday before precipitation tapers off.

Farther west, another closed low is forecast to move across the
Pacific Northwest beginning Monday morning, with high elevation
snow for the Oregon Cascades and the Blue Mountains, then
especially across the central Idaho ranges by Monday night into
early Tuesday.  Snowfall totals in the 4-8 inch range are likely
for the higher elevations of these areas, mainly above 8000 feet. 
By later Tuesday, light to moderate snow is expected from the
Bitterroots to the Big Belts and Absaroka Range, and then reaching
the northern Colorado Rockies by early Wednesday as the upper
shortwave moves east.

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

Hamrick/Pereira