Monday 10 a.m.
Cooler air advanced from the Great Lakes to the Middle and North Atlantic states during the weekend. The high pressure area marking the center of the cool air mass is moving toward the Carolinas now, and a return southwesterly flow will sponsor a warmup until the next cold front arrives. That flow should be on a line from central New England to southern Illinois on Wednesday, and it will drift southward and stall on a line from North Carolina to southern Missouri on Thursday.
Some showers will accompany the front, and some rain may break out on the north side of it later in the week. At the end of the week and into the weekend, there is quite a variation in model solutions, with some suggesting rain spreads across the Middle Atlantic states then into New England during the weekend.
The dominant cloud type in the summertime is the cumulus. Cumulus clouds can still grow in the fall and winter, but there is less solar heating, and thus less fuel to get these clouds to grow. The clouds in this picture are not associated just with fall, but in summer the same situation would lead clouds with greater vertical development.
Wet weather is coming toward the Northeast, and episodes of rain may be spread out over a two- to three-day period. Supporting this idea is this satellite/radar image from mid-morning Monday showing pockets and bands of rain affecting several areas.
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: