Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
426 AM EDT Fri Apr 09 2021

Valid 12Z Fri Apr 09 2021 - 12Z Mon Apr 12 2021


...Pacific Northwest to the Northern Plains...
Days 1-3...
A well-defined shortwave trough and its associated frontal band
are forecast to drop from western Canada into the Pacific
Northwest, bringing another round of mountain snow beginning late
Friday and continuing into Saturday.  Probabilities for
significant accumulations have increased with the overnight model
runs, with the latest WPC PWPF indicating storm total
accumulations of 4-inches or more likely down into the northern
Cascade passes, with accumulations of 8-inches or more likely
across the higher elevations of the northern Cascades and
Olympics.  The system will quickly shift east, bringing snow into
the northern Rockies on Saturday, with some potential for
significant accumulations across the northern Idaho, western
Montana, and northern Wyoming ranges.  As the system continues
east, models show a broad upper low developing over the northern
Plains Sunday night into Monday, with rain changing to snow across
North Dakota.  Probabilities for widespread heavy accumulations
are low at the moment, however some models do suggest a developing
band that could produce local amounts of at least a few inches
across portions of western North Dakota late Sunday into Monday. 

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

Pereira