Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
411 AM EST Fri Feb 14 2020

Valid 12Z Fri Feb 14 2020 - 12Z Mon Feb 17 2020


Days 1-3...

...Pacific Northwest to the Northern Rockies...
A shortwave trough passing east across the northern Rockies Friday
morning is expected to produce a few inches of snow across the
higher elevations of the northern Rockies, from northern Idaho and
western Montana to western Wyoming, before moving east into the
northern Plains by Friday evening.  Meanwhile, onshore flow in its
wake will continue to support snow showers, with additional light
accumulations expected across the Olympics and northern Cascades
as well.

Organized heavier precipitation is forecast to return to the
Northwest as a low-amplitude shortwave diving southeast from the
Gulf of Alaska toward British Columbia pushes a frontal boundary
and corresponding plume of deeper moisture into the Northwest on
Saturday.  Snow levels are expected to briefly rise on Saturday,
before falling once again on Sunday.  Heavy mountain snows still
appear likely, with areas impacted expected to include the
Cascades, Blue Mountains, and the northern Rockies from northern
Idaho and western Montana to western Wyoming.  For the 24-hr
period ending 00Z Mon, WPC PWPF suggests local amounts of a foot
or more are likely across these areas.

By late Sunday, models show the upper pattern beginning to amplify
across the West as energy from the Gulf of Alaska continues to dig
southeast across western Canada into the U.S., with measurable
snows likely extending into the northern Utah and Colorado ranges
Sunday into early Monday. 

For Days 1-3, the probability of significant icing (0.25 inch or
greater) is less than 10 percent.

Pereira