Thursday 10 a.m.
The high pressure area marking the center of the chilly air mass that is now over the Great Lakes and Northeast will move eastward and will be offshore tomorrow night. The ensuing warm-up occurs in two stages. First, there is an increase in sunshine with a decrease in wind. This makes it more comfortable.
Then, a southwesterly flow gets under way. That flow extracts the last of the chilly air and allows warm air to assume control. When fully in place, the warm air mass will be capable of sending temperatures toward 90 if there is full sunshine. We expect temperatures to reach or surpass 80 degrees from Virginia to near New York City.
Meanwhile, locally violent thunderstorms will cross the Plains. Please see our severe weather reports and numerous news items as this situation develops. By Monday, the northern end of the cold front that sponsors the thunderstorms will move to northern New England.
The question then becomes how far south the front will progress. Behind the front, it will turn chilly, and with a cold high pressure area moving into eastern Canada, a chilly northeasterly flow is likely to advance down the coast through at least most or all of New England. These fronts usually move the farthest south when the ridge axis aloft is west of the Eastern Seaboard. The computer models for early next week suggest that will not be the case in the coming setup. This video has more.
In central Pennsylvania, yesterday was March-like and it snowed for a while at many spots. In response to cold air aloft and temporary heating at ground level, large cumulus clouds towered into the sky and a series of showers/snow showers developed. This picture was taken a few minutes before one of these showers arrived.
On this map from 10 a.m. ET Thanksgiving Day, you can see the high pressure area that is causing dry and mild weather in the East and the cold front farther west.
During the late afternoon and early evening hours, the cold front of a knife will slice through the turkey and cause it to accumulate 1-2 inches on plates...
This satellite picture shows clouds over parts New York and Pennsylvania, as well as areas of low clouds, fog and snow cover from Michigan to Illinois. Most of the Northeast should have at least some sunshine through Thanksgiving Day.
As we go through the week, the flow aloft over the East will become southwesterly. This will promote a major warmup. This map shows the projected upper-air flow for Thanksgiving afternoon:
A major snowstorm will affect the area from Iowa to Michigan tonight and tomorrow. At first, snow can melt on streets, but as it continues and the temperature drops, the area impacted by slippery conditions will increase dramatically. This map shows expected accumulations:
This map shows two cold fronts in the northeast quarter of the nation; 9 a.m. ET temperature are plotted. The isobars are closest together over the central and western Great Lakes, and this is where the strongest winds were occurring.