Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
414 PM EDT Thu Mar 26 2020

Valid 00Z Fri Mar 27 2020 - 00Z Mon Mar 30 2020


Days 1-3...

...Southwestern U.S. to the Upper Midwest...
A low-to-mid level front dropping southeast across the central
Rockies and Southwest will continue to support periods of
organized mountain snows from the coastal ranges of Southern
California to the central Rockies into early Friday.  As a
well-defined shortwave moving through the base of the associated
upper trough begins to pivot east, this will begin to push the
front more progressively to the east, limiting the potential for
additional widespread heavy amounts across the southwestern U.S.
and Great Basin.  However, as the trough moves through the Four
Corners region, a developing surface cyclone over eastern Colorado
will increase the potential for impactful amounts over the higher
elevations of eastern Colorado and southeastern Wyoming on Friday.
 WPC PWPF is showing high probabilities for accumulations of
8-inches or more from the Front Range to the Laramie Mountains. 
This system is expected to rapidly amplify as it moves across the
central Plains on Saturday.  With the exception of the NAM,
consensus of the 12Z deterministic guidance showed mostly rain or
a rain/snow mix in the associated comma-head across eastern
Nebraska and South Dakota to southern Minnesota on Saturday, with
some greater potential for accumulating snow across northern
Wisconsin, the Minnesota Arrowhead the U.P. Saturday night into
Sunday.

...Northeast...
Warm advection precipitation associated with the low moving into
the Great Lakes will spread into northern New England on Sunday. 
Cold air wedge remaining in place will support mixed
precipitation, with accumulating snows likely across northern New
Hampshire and northern Maine.

...Pacific Northwest to the Northern Rockies...
A weak upper trough is expected to bring mountain snows back into
the Pacific Northwest and northern Rockies as it approaches the
coast on Saturday.  As this system drops to the south,
strengthening onshore flow ahead of a better-organized system
moving south from the Gulf of Alaska will increase the potential
for heavy accumulations over the higher elevations of the
Olympics, northern Cascades and portions of the northern Rockies
on Sunday.

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

Pereira