Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
426 AM EDT Fri Oct 29 2021

Valid 12Z Fri Oct 29 2021 - 12Z Mon Nov 01 2021


...Northern Rockies to the central High Plains...
Days 1-3...
An amplifying upper trough is forecast to drive a cold front
east-southeast across Montana.  A period of post-frontal upslope
flow will support some locally heavier amounts in the Lewis
Range/Glacier National Park where snow levels are expected to drop
down to around 3000ft tonight. This will allow some light
accumulations onto the High Plains. Day 1 WPC probabilities for
have increased back a bit with moderate probabilities for 6 or
more inches for the eastern slopes of the Lewis Range. Some low
probabilities for 4 or more inches remain for the Bighorn
Mountains on Day 2 as the front pushes south over WY Saturday
morning.

The cold front progresses all the way to the southern Plains, but
some where in the southeast WY/western Neb into northern CO area
is the likelihood of bands of snow to form Saturday night through
Sunday with low level convergence from the building surface ridge
in from Alberta and under the right entrance region of the
westerly jet on the southern end of the upper trough. As of now
there are low probabilities for 2 or more inches over much of the
Neb Panhandle and southeast WY for Day 3, though there is
potential for locally enhanced amounts should be band be slow to
progress.

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

Jackson