Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
412 PM EST Fri Feb 28 2020

Valid 00Z Sat Feb 29 2020 - 00Z Tue Mar 03 2020


...Great Lakes...
Ongoing lake effect snow showers will continue downwind of the
Lower Lakes into the overnight, before diminishing on Saturday as
high pressure and drier air move into the region.  Additional
heavy accumulations are possible, particularly east of Lake Erie
where WPC PWPF shows the potential for local accumulations of
6-inches or more across portions of western New York and
northwestern Pennsylvania late Friday into early Saturday.

...Cumberland Plateau/Central and Southern Appalachians...
Snow showers will continue Friday evening as deep, cyclonic,
westerly flow persists.  Embedded mid-level energy moving through
the broader scale flow may support periods of heavier
precipitation -- raising the potential for impactful accumulations
across the Cumberland Plateau and the central to southern
Appalachians.  WPC PWPF shows high probabilities for additional
accumulations of 2-inches or more along the VA-KY and TN-NC
borders late Friday into early Saturday.

...Western U.S....
A well-defined shortwave dropping southeast through the
northeastern Pacific is expected to move east across the
Northwest, bringing mountain snows back into the Northwest Friday
night into Saturday, with heavy accumulations likely for the
higher elevations of the Olympics and Washington Cascades.

Models show this leading energy moving east into central Canada as
a trailing shortwave digs farther south along the West Coast. 
Models continue to show strong low-to-mid level frontogenesis
supporting widespread mountain snows from the northern and central
Rockies to the California mountains.  Areas impacted late Saturday
into Sunday are expected to include the Sierra, northern Nevada
mountains and the northern Utah and western Wyoming ranges. 

The upper trough is expected to continue amplifying, with a upper
low closing off over Southern California late Sunday-early Monday.
 This will bring snows farther south into the Southern California
mountains and the higher elevations of the Southwest, as well as
the Colorado and northern New Mexico Rockies.

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

Pereira