Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
330 PM EDT Mon Oct 30 2023

Valid 00Z Tue Oct 31 2023 - 00Z Fri Nov 03 2023

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

Lake effect snow showers will continue through today/tonight
downwind of Lake Superior and Lake Michigan as west-northwesterly
winds move over the still warm waters. The greatest accumulations
through this evening will be found across portions of the Keweenaw
Peninsula in Upper Michigan where WPC snow probabilities for at
least 4" through tonight remain above 80 percent. As a cold front
slowly slides eastward through the eastern U.S. later today,
westerly to northwesterly winds will develop off Lake Erie and
Lake Ontario and with the arrival of much colder air, lake effect
precipitation is expected though with more marginal boundary layer
temperatures, snow accumulations off these lakes will be minimal.

Across the Upper Midwest, a vigorous/potent shortwave trough
embedded in the broad longwave trough is currently moving
southeastward through North Dakota this afternoon. Steepening low
level lapse rates and strong forcing will produce convective show
showers later this afternoon and evening from eastern North Dakota
through portions of central/northern Minnesota overnight. Narrow
bands of intense but brief snow squalls will be possible and the
CIPS Snow Squall Parameter remains above 1 in these areas. This
wave will reach western to southern Wisconsin and northern
Illinois tomorrow morning/afternoon and another round of
convective snow showers/squalls are expected which could produce
locally intense but brief snow rates. Some of these snow
showers/squalls may be strong enough to cause rapid declines in
visibility and lead to travel disruptions.

As the shortwave energy passes over Lake Michigan Tuesday, its
interaction with the warm waters should lead to more vigorous snow
showers and snow bands downwind of Lake Michigan. This could focus
heavy snowfall rates along the western counties of Michigan and
the 12Z HREF shows near 40 percent chances of seeing 1" hourly
snow totals during the afternoon hours and the latest WPC snow
probabilities shows a slight chance (20-30%) of seeing 4" totals
across west-central Michigan. Meanwhile, the lake effect snows
will continue off Lake Superior in the wake of the strong
shortwave and WPC snow probabilities for at least 4" are between
40-60 percent. Finally, a few locations downwind of Lake Erie, in
far northeast OH, northwest PA, and southwest NY, may see a few
stronger lake effect snow bands where WPC snow probabilities for 4
inches peak at 20 percent Tuesday/Tuesday night. 

Taylor