Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
332 PM EDT Fri Oct 09 2020

Valid 00Z Sat Oct 10 2020 - 00Z 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 upper
level jet dynamics, 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.

Pereira