Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
330 AM EST Tue Nov 07 2023

Valid 12Z Tue Nov 07 2023 - 12Z Fri Nov 10 2023

...Northwest, California through the Northern Rockies and then
Colorado...
Days 1-2...

A broad positively-tilted upper trough shifts onshore today,
digging as far south as central CA. The precip focus is this
morning over the Cascades to northern Rockies with snow levels
generally around 5000ft. Ridging builds in from the Pacific
tonight, shunting precip farther inland. Day 1 snow probs for >6"
are moderate (40-60% over the higher WA/OR Cascades, the
Bitterroots, and the ridges near Glacier NP including Mission
Ridge which is a favorite for CAMs to maximized precip on in
westerly flow.

The base of the trough shifts from NV into UT tonight with
downstream lee-side troughing east of the CO Rockies providing an
upslope flow and added lift from the right entrance region of a
SWly jet overhead. 00Z guidance continues a downward trend in
precip with Day 2 snow probs generally lower moderate (20 to 50%)
for >6" along the Front Range to the Continental Divide.


Northern Plains, Northern Great Lakes, Northeast...
Days 1-3...

Warm advection precipitation will spread out across North Dakota
today ahead of the wave moving out of the northern Rockies. Some
mixed precipitation, including freezing rain, is likely this
morning, with 10% Day 1 probabilities >0.1" ice accum over
northeastern ND.

Some light precipitation, with mostly limited winter weather
impacts shifts across the northern Great Lakes region late tonight
into Wednesday with a couple inches snow possible inland from the
North Shore of Lake Superior in MN.

Meanwhile, as the trough in the West continues to advance, surface
low pressure developing over the central High Plains late today
will advance northeast into the mid-Mississippi Valley on
Wednesday. Increasing moisture and ascent will support a
broadening precipitation shield ahead of the advancing low, with
some wet accum in mainly the eastern U.P. of Michigan.

Cold high pressure over the Northeast will give way to the
advancing low, with precipitation spreading across the Northeast
late Wednesday into Thursday. Following a brief period of
snow/sleet at the onset, warming air aloft will support a
changeover to ice at least in pockets of eastern New York into
central New England. 20 to 50% probabilities for >0.1"
accumulating ice extend from the Catskills to the Adirondacks via
the Hudson Valley with similar probs for the Berkshires, and
Greens.


Jackson