Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
327 AM EST Sat Dec 30 2023

Valid 12Z Sat Dec 30 2023 - 12Z Tue Jan 02 2024

...California...
Day 1...

A potent upper level trough tracking into the West Coast this
morning is directing a plume of 850mb moisture into the Sierra
Nevada. Snow level will drop to as low as 6,000ft thanks to the
colder temperatures associated with the upper trough and the
strong upslope flow enhancing precipitation rates. Snow will
dissipate Saturday night as the upper trough tracks into the
Southwest. WPC PWPF depicts moderate chances (40-60%) for >4" of
snowfall in the highest peaks of the central and southern Sierra
Nevada. The WSSI depicts Minor impacts for most elevations above
6,000ft, but Moderate Impacts above 8000ft. Treacherous travel and
delays in the higher Sierra Nevada are possible in these areas
through Saturday evening.

...Upper Great Lakes...
Days 1-2...

A clipper system diving south from Ontario will strengthen as it
tracks into the Upper Midwest Saturday night. As the low tracks
south into northern Wisconsin, northeasterly flow will increase
over Lake Superior and result in lake effect snow bands over
northern Wisconsin. While other snow showers will breakout in
parts of the Midwest and Great Lakes, it is northern Wisconsin and
the western U.P. of Michigan that will have slightly better odds
for heavier snowfall. WPC PWPF features low-to-moderate chances
(20-50%) for snowfall >2" in these areas. Some slick spots of
roads are possible in areas where heavier snowfall rates occur.

...Central Appalachians...
Days 1 & 3...

Lingering northwesterly flow will keep periods of snow in the
forecast across parts of the central Appalachians. After a break
in the snow Saturday night and into Sunday morning, the clipper
system responsible for light snow in parts of the Midwest and
Great Lakes will make its way into the northern Mid-Atlantic
Sunday night. This will bring a rejuvenated surge of upslope flow
and some modest moisture aloft. Periods of mountain snow will
develop once again from the Potomac Highlands on north to the
Laurel Highlands and Allegheny Mountains Sunday night and into New
Year's Day. WPC PWPF sports low-to-moderate chances for >2" of
snow in eastern West Virginia and western Garrett County, MD on
north to portions of the southern Laurel Highlands. If there is
one area that is the odds on favorite to see >4" of snow, it would
be the higher peaks of eastern West Virginia. WPC PWPF shows,
however, that odds are rather low as probabilities are topping out
around 10%. Some hazardous travel conditions are possible this
morning due to the lingering upslope snowfall, and again Sunday
night into New Year's Day as another minor accumulating snowfall
event unfolds.

The probability of significant ice across the CONUS is less than
10%.


Mullinax