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

Valid 12Z Sat Nov 12 2022 - 12Z Tue Nov 15 2022

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

A cold front set to usher anomalously cold temperatures south and
east across the Great Lakes will trigger lake effect snow bands
from the U.P. of Michigan and western Michigan to the typically
favored areas downwind of Lakes Erie and Ontario. As 850mb
temperatures ranging between -10C to -15C track across the warmer
Great Lakes (Lakes Superior and Michigan Day 1, then Lakes Huron,
Ontario, and Erie on Day 2), delta-Ts as high as 15-20C and a
surface trough aiding in source of lift at low levels supports
lake effect snow banding. Latest WPC probabilities indicate there
is a 50-60% chance for >6" of snowfall on Day 1 in portions of
Michigan's U.P. with up to 30-40% probabilities in western
Michigan. Snow bands will be less intense downwind of Lakes Erie
and Ontario, but there are still some 10-20% probabilities of >4"
of snowfall in far western New York to the south of Buffalo
through Saturday night. Lake effect snow bands will persist on
Sunday throughout the region but the stronger low level winds will
begin to subside by Sunday evening. By Monday, high pressure will
have built in over the Great Lakes and just about all lake effect
snow bands are forecast to dissipate.

...South Central Plains & Middle Mississippi Valley...
Day 3...

A potent upper level shortwave trough tracking through the Four
Corners region on Sunday will produce periods of mountain snow in
the Southern Rockies Sunday night. Meanwhile, to the north, an
expansive area of Canadian high pressure will anchor subfreezing
and climatologically colder than normal temperatures across the
Southern Plains and Middle Mississippi Valley. There is good
ensemble agreement on the upper trough placement and strength over
eastern New Mexico by 12Z Monday morning. There is also good
agreement on the track of the 850mb low with both Euro & GEFS
ensemble means placing the 850mb low in the Texas Panhandle by 12Z
Monday. The area with the best odds of seeing heavy snowfall will
be oriented 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. WPC probabilities were in the 30-40%
range for >4" of snowfall in the Sangre De Cristos of northern New
Mexico with 10-20% probabilities in the far northern Texas
Panhandle and in the Oklahoma Panhandle. By Monday night, snow
will push farther north and east into the Middle Mississippi
Valley as the 850mb low is currently forecast to track across the
Ozarks. There is a swath of >2" snowfall probabilities in the
Ozarks of southern Missouri and northwest Arkansas that are as
high as 20-30%. Where uncertainty resides is in the orientation of
700mb frontogenesis tracking across southern Missouri Monday night
and the influence from the upper low over the Northern Plains.
Where the best 700mb forcing resides and the track/orientation of
the upper low in Oklahoma will determine whether heavy snow ends
up in central Missouri or farther south towards the
Mississippi-Ohio Confluence.

The probability of significant icing is less than 10 percent.

Mullinax