Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
437 AM EDT Sat Oct 10 2020

Valid 12Z Sat Oct 10 2020 - 12Z Tue Oct 13 2020


Days 1-3...

...Pacific Northwest to the Northern Rockies...
A well-defined mid-to-upper level shortwave trough is forecast to
move across the northwestern U.S. on Saturday.  Favorable
left-exit region upper level jet dynamics into the trough base, in
addition to a long fetch of moisture, are expected to support
widespread precipitation across the region, with orographic
effects forecast to help produce locally heavy amounts.  While
snow levels are expected to drop significantly behind the
associated cold front, heavy snow accumulations through late
Saturday will likely be confined to the highest peaks of the
Cascades.  Onshore flow will continue to support showers across
the Northwest through Sunday before a mid-level shortwave brings a
return of organized heavier precipitation back into the region
Sunday night. This will likely produce several more inches of snow
across the highest peaks of the northern Cascades.

Meanwhile to the east, mountains snows are forecast to advance
east into the mountains of northeastern Oregon and the northern
Rockies beginning Saturday night and then continuing through
Sunday into Monday.  Locally heavy accumulations are possible
along the higher elevations the Wallowa Mountains in northeastern
Oregon, as well as along the central Idaho, western Montana and
western Wyoming ranges.

The probability of significant icing is less than 10 percent.

Hurley/Pereira