FOUS11 KWBC 080907
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
407 AM EST Sat Nov 8 2025

Valid 12Z Sat Nov 08 2025 - 12Z Tue Nov 11 2025

...Strong and deep low develops over the Great Lakes Sunday with
notable Lake Effect Snow through Tuesday...


...North-Central Plains to southern Michigan... Day 1...

Shortwave trough/vort max over eastern MT early this morning swings
southeast to southern Iowa today and Ohio tonight. Ongoing snow
banding over the Dakotas ahead of this wave shifts southeast
through western Iowa this morning where marginal thermals should be
overcome in the better banding to allow accumulations. Day 1 WPC
probabilities for >4" are around 10 percent in west-central IA.
Forcing intensifies over the Midwest late tonight into Saturday.
There is a moderate threat for CSI banding along the southern MI
border due to fgen overlapping the DGZ and driving ascent into a
region of theta-e lapse rates of 0C/km. This may lead to snowfall
rates of 1.0"/hr at times per the 00Z HREF. Day 1.5 snow
probabilities for >4" snow are 30-60% over northern IN and southern
MI up to the Detroit metro as well as far northwest OH.

...Lake Effect/Enhanced Snow tonight through Tuesday...
A reinforcing shortwave trough rounding a deep low shifting south
from Hudson Bay crosses the Upper Midwest tonight with a deep
second lobe developing over Michigan Sunday that swings south
before tracking over the Interior Northeast Monday night. The
surface low rapidly develops over Ohio tonight downstream of the
initial shortwave trough. The reinforcing trough importantly slows
the progress of the surface trough along the Northeast coast Sunday
which prolongs the following flow over the Great Lakes for lake
effect/enhanced snow tonight of Lake Superior shifting through all
the Great Lakes before easing off Lake Ontario on Tuesday.
Strong CAA brings a winter-like airmass to the region, headlined
by 850mb temperatures between negative 10 and 12 degrees C. This
cold air (near or below the 10th climatological percentile) over
the warm Great Lakes (temperatures of +10 to +15C) will result in
an impressive convective environment with model soundings
indicating steep lapse rates and deep mixing heights to near or
above 700mb. Given lake temp and 850mb air temp delta Ts of 20 to
30C, the environment will be rather supportive for lake
effect/enhanced snow production.

North-northwest to northerly surface winds along with increasingly unidirectional winds aloft will act on the instability and support
the development of a few prominent north-south lake effect snow
bands, particularly downwind of Lake Superior tonight through
Monday, Lake Michigan Sunday night through Monday, Lakes Huron and
Erie Sunday night through Monday night, and Lake Ontario Monday
night/Tuesday.
Day 2 WPC probabilities for >6" are over 80% in the Huron Mtns of
the U.P. of MI and up to 40% in the Porcupine Mtns while 40-80% for
portions of the western L.P. shoreline and all of the Indiana
shoreline. Day 3 WPC probabilities for >6" are 60% over Northern
Indiana for continued banding threats (most notably in the 00Z
experimental RRFS), around 80% near Port Huron, MI (the exact wind
direction will determine which side of the border gets hit worst), 40-80%
south of Lake Erie east of Cleveland, and around 10% in the Tug Hill.

Cold upslope northwesterly flow and a moist fetch from Lake
Michigan will also cause upslope snow showers for the Central
Appalachians Sunday night through Monday night with Day 3 WPC
probabilities for >6" 40-70%.

Jackson

$$
--- SBBSecho 3.28-Linux
* Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (618:250/1)