Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
417 AM EST Sat Feb 15 2020

Valid 12Z Sat Feb 15 2020 - 12Z Tue Feb 18 2020


Days 1-3...

...Pacific Northwest to the Northern and Central Rockies...
Organized, heavy precipitation is expected to return to the
Pacific Northwest and northern Rockies as mid-level energy
embedded within progressive northwesterly flow moves from the Gulf
of Alaska into western Canada and the Pacific Northwest.  This
will push a frontal band and corresponding plume of deep moisture
into the region.  Snow levels are forecast to briefly rise on
Saturday before falling once again as the cold front pushes east
across the Northwest into the northern Rockies late Saturday and
early Sunday.  Locally heavy accumulations remain likely for the
higher elevations of the Cascades, Blue Mountains and the northern
Rockies from northern Idaho and western Montana to the eastern
Idaho and western Wyoming.  WPC PWPF continues to show high
probabilities for accumulations of a foot or more across these
areas on Day 1 (ending 12Z Sun).

Energy will continue to dig southeast, with deeper moisture
pushing south into the central Rockies -- raising the potential
for heavy snows across the northern Utah, southern Wyoming and
western to central Colorado ranges on Sunday into Monday.  WPC
PWPF shows high probabilities for accumulations of a foot or more
across these areas, while also indicating high probabilities for
additional heavy accumulations of a foot more across portions of
the western Wyoming ranges on Day 2 (ending 12Z Mon) as well.

...Northern Plains to the Upper Great Lakes...
Energy moving along the leading edge of the western U.S. trough is
expected to interact with energy dropping southeast from western
Canada into the northern Plains -- supporting the development of a
weak surface wave that is forecast to lift northeast from the
lower Missouri valley toward the Upper Great Lakes on Monday. 
Light to moderate snows are expected on the northwest side of the
low track, with guidance showing pretty good potential for
accumulations of 4-inches or more across portions of eastern
Wisconsin to Upper Michigan on Monday.

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

Pereira