Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
406 PM EST Sat Nov 12 2022

Valid 00Z Sun Nov 13 2022 - 00Z Wed Nov 16 2022

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

Lake effect snow bands will continue to set up in favored snow
belts from the western to eastern the Great Lakes through tonight
and persist through Sunday night for the eastern Lakes as an upper
trough swings through. 850mb temperatures ranging between -10C to
-15C over the warmer Great Lakes will bring delta-Ts as high as
15-20C supporting lake effect precip banding that should begin as
rain off Lakes Erie and Ontario tonight before changing over to
accumulating snow. WPC Probabilities for 4 or more inches are
moderate to high off all, but Lake Ontario where the NW to SE
oriented band is currently progged in the lower elevation area of
the western Mohawk Valley. Localized risk areas for 8 or more
inches remain for Day 1 over the UP into northernmost WI and along
the western shore of Lake Michigan.

...Northern Maine...
Days 1/2...

A strengthening upper trough swinging across the Great Lakes
tonight begins to take on a neutral tilt Sunday as it lifts over
New England. The surface wave develops into a low off the New
England coast Sunday, with the central pressure dropping below
1000mb by the time it reaches New Brunswick Sunday evening.
Increasing cold air advection and low to mid level frontogenesis
should allow snow bands to develop over northern Maine Sunday
afternoon. Though the system is progressive, there is a risk for
heavy snow in these bands with the 12Z Sun-12Z Mon snow
probabilities around 10 percent for 6 or more inches over
northwestern Maine.

...Southern Rockies, South-Central Plains to the Upper Midwest...
Days 2-3...

A closed low currently over the OR/CA border opens into a
positively-tilted shortwave over the Four Corners by late Sunday
and over New Mexico Sunday night. Periods of mountain snow across
the CO/NM border can be expected Sunday night with low to moderate
probabilities for 4 or more inches for the San Juans/Sangre de
Cristos.

Meanwhile, to the north, an expansive area of Canadian high
pressure will anchor subfreezing and climatologically colder than
normal temperatures across the Southern Plains through the Upper
Midwest. Confidence has increased on the 850mb low along the
southern NM/TX Panhandle border Monday morning which tracks east
over the Red River of the South Monday. Bands of snow north of
this low are expected to develop on the northern and western flank
of the 850mb low as a plume of 850mb moisture flux is advected
north via a LLJ and wraps around the 850mb low over the OK/TX
Panhandles and spread into/across KS into the evening. Day 2 WPC
probabilities for 4 or more inches have increased 20-30% in the
far northern TX Panhandle, the eastern OK Panhandle and into
southwest KS.

While the surface low tracks southeast to the Gulf, an inverted
trough develops up the entirety of the Miss Valley Monday night
with areas/swaths of light to locally moderate precip across this
entire region. Day 2.5/3 snow probabilities for 2 or more inches
are low to moderate for the AR Ozarks, east-central KS and MN/WI.
Much of this precip is warm air advection on
southerly/southeasterly flow, though enough cold air is present to
warrant snow for areas north of the lower MS Valley. This
southeasterly flow over Lake Superior does allow 30 to 40 percent
day 3 probabilities for 4 or more inches for the North Shore of
MN.

South-central Appalachians...
Day 3...

There is a risk for light icing as precip moves into the
south-central Appalachians Tuesday morning. Enough cold air looks
to be in place Monday and it may be clear enough Monday night
prior to cloud up to allow enough radiational cooling to have some
sub-freezing air in valleys as warm air advection precip moves
into the area. As of now there is a 10-20% chance for a tenth inch
of ice in southwest Virginia with timing of cooling and precip key
to ice glazing.

Jackson