Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
349 PM EDT Wed Oct 30 2019

Valid 00Z Thu Oct 31 2019 - 00Z Sun Nov 03 2019


Days 1-2...

...Central Plains to the Upper Great Lakes...
Upper trough digging through the Northern Plains will begin to
tilt negatively as it crossed the Great Lakes. This will induce
surface cyclogenesis, and this feature will lift northeast west of
the Appalachian Mountains. While much of this system will be too
warm for snow, a stripe of colder temperatures and wintry
precipitation is likely on the NW side, from far NE KS up into
Michigan. While guidance still differs on the exact track and
placement of heaviest snowfall, there is reasonably good
consistency today in a stripe of moderate to heavy snow from far
NE MO through SE IA, NW IL, SE WI, and into the northern L.P. of
MI. This heavy snow will form beneath the comma head/deformation
band pivoting slowly across the region, coincident with modest
850-600mb fgen. As p-type will transition from rain to snow as
cold air floods southeastward, accumulations will be somewhat
limited as some of the QPF falls out as liquid. Once the
transition occurs, bursts of moderate to at times heavy snow rates
are possible where the best forcing overlaps the DGZ. The longest
period of snowfall is likely in the vicinity of the CWAs of
DVN/LOT/MKX where WPC probabilities are as high as 30% for 6
inches of snowfall. Lighter amounts are likely as far south as NE
KS, and as far north as the U.P. of Michigan. There has been a
subtle trend colder and deeper with the system, especially west of
Chicago, so there is potential for isolated heavier amounts within
the pivoting comma head across N IL and into S WI, but
probabilities for 8 inches are 10% or less.

The probability of significant icing is less than 10 percent all 3
days.

Weiss