Cold air sweeping across the Great Lakes from Canada will flip the snow switch on from northeastern Ohio into western Pennsylvania, western New York and the Appalachians on Wednesday night into Friday morning.
While areas like Cleveland, Erie and Buffalo will have only a few wet snowflakes mixing in from time to time, with mostly rain squalls around, favored inland snowbelt regions such as Bradford, Pa., and New York state's Tug Hill Plateau will have moderate to significant accumulation.
In fact, by the time Friday morning rolls around, parts of the Tug Hill just east of Lake Ontario could have 3-9 inches of snowfall, which would be the heaviest so far this season, and the greatest amount since last winter.
A less significant, though still potentially disruptive 1-3 inches of snowfall is expected in areas such as Jamestown, N.Y., Du Bois, Pa. and Pierpont, Ohio.
Motorists traveling I-80 or the Pennsylvania Turnpike through the higher terrain of central and western Pennsylvania should prepare for rapidly changing weather conditions.
Rain showers will quickly change to snow in higher elevations, and low visibility and slippery roadways are an accident waiting to happen for anyone traveling too fast for the road conditions.
The same can be said about I-86 in southwestern New York and I-70 in Maryland and West Virginia, where snow of 1-3 inches will also impact the roads in the higher terrain.
A limiting factor that will prevent this from being a more widespread, severe event is warm water temperatures. Water temperatures in lakes Erie and Ontario are running a few degrees above where they should be for this time of year.
As of Oct. 22, the Lake Erie water temperature observed at Buffalo was a mild 60 degrees Fahrenheit.
This reading is the second highest value since 1927, when record keeping began, though the temperature has been in the 60s eleven times since then for this date.
The warm water temperatures will act to moderate the cold air mass passing over the lakes, leading to less snow overall and just plain rain, possibly mixing with snow, right at the lakefronts.
The lake-effect rain and snow squalls will gradually come to an end on Friday morning as the winds off the lakes lighten, and the air temperatures warm.
No snow will reach the I-95 corridor of New England and the mid-Atlantic, but brisk winds and November-like cold air will.