Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
430 AM EDT Sat Oct 19 2019

Valid 12Z Sat Oct 19 2019 - 12Z Tue Oct 22 2019


Day 1-3...

An amplifying shortwave trough will bring an additional round of
organized, heavier precipitation to the Pacific Northwest and the
northern Rockies today. In additional to upslope flow, left-exit
region upper jet dynamics will help to accentuate precipitation
rates across the northern Cascades and the northern Rockies. Heavy
snow accumulations are expected to extend south along the WA/OR
Cascades, where snow levels are expected to remain below 5000ft.
The threat for locally heavy snow accumulations will also extend
east into the mountains of southeastern Washington and
northeastern Oregon, as well as the Rockies from northern Idaho
and western Montana to western Wyoming.

As the upper trough continues to amplify and shift east on Sunday,
mid-level energy dropping into the trough will continue to support
snow showers, producing some locally heavy accumulations across
the higher summits of the northern Cascades, as well as the
northern into the central Rockies. 

Upslope flow along with supporting cold air on the backside of an
deepening low is expected to produce at least a few inches of snow
across the Black Hills by late Sunday. Elsewhere across the
Plains, low level warm air is expected to produce mainly rain.

On Monday, apart from the higher summits of the northern Cascades
and Rockies, a well-defined ridge moving east and a low level high
moisture plume is expected to limit the potential for heavy snow
across much of the western U.S.


The probability of significant icing is less than 10 percent Days
1-3.

Jackson