Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
459 AM EDT Mon Apr 12 2021

Valid 12Z Mon Apr 12 2021 - 12Z Thu Apr 15 2021


...Northern Plains...
Days 1-2...
Periods of snow are expected to wrap around the backside of a
closed low as it drifts slowly east from the Dakotas to the Upper
Great Lakes over the next couple of days.  Through early
Wednesday, additional snow accumulations of 4-inches or more are
likely across much of northern and central North Dakota into
northwestern Minnesota, with locally heavier accumulations of
8-inches or more possible across portions of northern North Dakota.

...Great Basin to the Central Rockies...
Days 2-3...
An amplifying shortwave is forecast to drop south from western
Canada into the Pacific Northwest on Monday, with a closed low
developing by early Tuesday.  This system is expected to then
settle into and elongate from the Great Basin into the central
Rockies on Wednesday and Thursday.  Left-exit region upper jet
forcing along with low-to-mid level frontogenesis will support
snows developing from northern Nevada to the central Rockies
beginning late Tuesday and continuing into Thursday.  This is
expected to produce areas of locally heavy accumulations.  These
areas include the Uinta mountains in northern Utah, the Wind River
Range in western Wyoming, and the Medicine Bow Mountains and Front
Range in southeastern Wyoming to central Colorado.  WPC PWPF shows
high probabilities for snowfall accumulations of 8-inches or more
across those areas by 12Z Thursday.  Lighter accumulations are
expected to extend east into the I-25 corridor from Cheyenne to
Denver.


For Days 1-3, the probability of significant icing (0.25-inch or
greater) is less than 10 percent.

Pereira