Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
412 AM EDT Sat Oct 26 2019

Valid 12Z Sat Oct 26 2019 - 12Z Tue Oct 29 2019


Days 1-3...

...Northern to Central Rockies/High Plains...
An upper level shortwave moving from the western Canada into the
Pacific Northwest will continue to dig south this morning, drawing
much colder air into the western U.S.  Snow is expected to move
south from the northern into the central Rockies and High Plains
through the weekend, with heavy accumulations possible from
southern Montana to eastern Colorado.

Upslope flow behind a strong cold front will continue to support
light to moderate snows across northwestern into central Montana
through early Saturday.  Models continue to show heavier amounts
developing farther south later into the day across southwestern
Montana and northwestern Wyoming.  Increasing upper divergence
along the left-exit region of the upper jet, in addition to low to
mid level frontogenesis, is expected to help support locally heavy
mountain snows across Yellowstone Country and Yellowstone NP, as
well as the Bighorn Mountains.  
 
By Saturday night and continuing into Sunday morning, the heavy
snow threat is expected to shift farther southeast into
southeastern Wyoming, with locally heavy accumulations expected
across the Shirley and Laramie mountains.  As temperatures fall,
low to mid level frontogenesis will help to extend the potential
for significant snowfall accumulations out into the High Plains
Saturday night, with several inches possible across portions of
southeastern Wyoming into western portions of the Nebraska
Panhandle. 

On Sunday and continuing into early Monday - as the upper level
trough continues to amplify and cold air plunges south, moderate
to locally heavy snow is forecast to shift south into the central
Colorado ranges, as well as along the I-25 corridor.  By Monday
morning, expect several inches of snow from the mountains and
foothills into the adjacent plains of eastern Colorado, including
the Denver metro area. 

By late Monday, expect snows to taper off across the central
Rockies and High Plains as the associated shortwave trough begins
to accelerate northeastward away from the region.

Meanwhile, snows are forecast to return to the northern Rockies as
another shortwave trough dives south into the region on Monday. 
This may produce another round of locally heavy accumulations in
the mountains of western Montana.

...Central Plains to the Great Lakes...
The shortwave trough moving east of the central Rockies on Monday
will accelerate northeastward from the central Plains through the
mid Mississippi valley and into the upper Great Lakes region late
Monday into early Tuesday.  With cold air in place, this will
produce a brief period of snow, with mainly light accumulations
expected from Kansas and Nebraska to the U.P. of Michigan.

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

Pereira