Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
330 PM EST Fri Nov 18 2022

Valid 00Z Sat Nov 19 2022 - 00Z Tue Nov 22 2022

...Eastern Great Lakes...
Days 1-3...

A long duration, intense lake effect snow event will continue
overnight as shortwave energy rounds the base of a northern stream
elongated trough extending from the Canadian Archipelago southward
into Hudson Bay. Two broad single band LES will continue off Lakes
Erie and Ontario this evening before slowly lifting northward on
slowly backing flow ahead of the main trough axis which is progged
to cross the Great Lakes Sat/Sat night. Strong CAA will continue
to bring the saturated layer through the DGZ over lake temps in
the low 50s (~11C) per buoys in Erie/Ontario. Extreme lake-induced
instability and high inversion heights will continue to support
lightning within the most intense snow bands this evening before
the bands off Erie/Ontario lift northward. Day 1 snow probs for an
additional 12+" are moderate (>40%).

Flow backs through Saturday morning to lift both snow bands
northward to a SW to NE trajectory and mostly into Canada. An
approaching cold front Saturday evening should veer flow and send
the bands back into NY Saturday evening until the cold frontal
passage Saturday night after which northwesterly flow and
multi-bands set up for Sunday. A surface ridge shifts east over
the Eastern Great Lakes Sunday evening, which finally brings an
end to this prolonged event. Snow probs D2 (00Z Sun - 00Z Mon) for
6 or more additional inches are high from northeastern Ohio
(northeast Cleveland suburbs) through Erie, PA to southwestern New
York (as well as near Oswego, NY). Local storm totals will exceed 
50" in areas just south of Buffalo.

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

The cold front associated with the upper trough moving through the
Upper Lakes tonight and early Saturday will cross Lake Superior
late tonight and Lake Michigan Saturday. Light snow associated
with the FROPA will transition to lake-effect snows behind the
front Saturday afternoon and continuing into early Sunday. Day 1
probabilities for at least 4 inches of snow are high (>70%) over
the northwestern U.P and much of the western coast of Lower
Michigan. 850mb temps will drop to -20C late Saturday before
rising on Sunday as upper heights rise as well, shutting off any
lingering light snow by Day 3. Day 2 probabilities for at least 4
inches are moderate over the eastern U.P. and northwestern Lower
Michigan as the flow backs from NW to WNW (and eventually W/WSW).


Key Messages for Lake Effect Snow in the Great Lakes:

--Periods of heavy lake effect snow will persist through Sunday
downwind of each of the Great Lakes. The most intense snowfall is
expected through tonight.

--East of Lakes Erie and Ontario, snowfall will at times be
accompanied by lightning, gusty winds, and rates of 3+ in/hr. This
will produce near zero visibility, very difficult to impossible
travel, damage to infrastructure, and may paralyze the hardest-hit
communities.

--Across parts of the Upper Peninsula and western Lower Peninsula
of Michigan, snowfall rates will reach 1-2 in/hr and combine with
gusty winds to produce near-zero visibility and dangerous travel.

--Total snow amounts of 1-2 feet are expected in many locations,
reaching 2-3 feet east of Lakes Erie and Ontario. Historic
snowfall exceeding 4 feet is likely around Buffalo, NY.

--Very cold air will accompany this event, with temperatures
forecast to be 20 degrees below normal across portions of the
region this weekend.



Fracasso/Jackson