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

Valid 00Z Sun Oct 27 2019 - 00Z Wed Oct 30 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 in
eastern WY to central Colorado.

Upslope flow behind a strong cold front will continue to support
light to moderate snows developing in Wyoming in response
to increasing upper divergence along the left-exit region of the
upper jet, in addition to low to mid level frontogenesis.
The higher amounts day 1 are targeted for the Wind River Mountains
to the WY front range, Laramie Mountains, and on the high Plains
of far northwest NE.

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 into the central and
southern Colorado ranges.  By Monday morning, expect locally heavy
snow from the mountains and foothills, with lighter amounts as
head head east across the adjacent plains of eastern Colorado,
including the Denver metro area.  Strong 700 mb convergence drives
maxima across the southern San Juans of CO into the Sangre
DeCristo Mountains west of Pueblo. More weighting was given to the
NAM Nest QPF and resultant snow, supported by the UKMET in the
Sangre DeCristo mountains.

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.

Snows are forecast to return to the northern Rockies as another
shortwave trough dives south into the region on Monday, with a 700
mb front progressing south across Wyoming Tuesday to near the CO
border. Low level convergence near the front and developing 700 mb
low(s) may produce another round of locally heavy accumulations in
the mountains of western Montana across Wyoming, with lighter
amounts in the Plains.


...Day 3 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 advecting into the
region behind the front, 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.

Petersen