Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
429 PM EDT Sat Oct 17 2020

Valid 00Z Sun Oct 18 2020 - 00Z Wed Oct 21 2020


...Northern Rockies/High Plains...
A series of sheared, mid-level shortwaves embedded within fast,
northwest flow will interact with a lingering frontal boundary to
support periods of snow into early next week.  Heaviest amounts
are expected to occur Sunday as a shortwave, accompanied by a
plume of deeper moisture, slide into the region.  Latest WPC PWPF
shows high probabilities for accumulations of 8-inches or more
along the western Montana ranges.  While periods of snow are
expected to continue into Monday and Tuesday, probabilities for
heavy amounts decrease as drier air begins to move into the region.

...Northern Plains and Upper Midwest...
Mid-to-upper level energy sliding through the West is expected to
amplify over the northern Plains on Tuesday.  Favorable upper
level jet forcing is expected to help produce a stripe of
accumulating snow across North Dakota to northern Wisconsin. 
However, the progressive nature of this system is expected should
help limit the potential for widespread heavy accumulations
through late Tuesday.

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

Pereira