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.
This table shows the ensemble means for the next two weeks at Philadelphia: It suggests that whereas it does turn cold, any snowfall looks quite limited.
It is too early to be confident about any forecast for Christmas Day (or even the week before). However, the GFS model does go out 16 days, and it has a cold look for the Northeast exactly one week before Christmas.
As the flow aloft becomes southwesterly, mild moist air will spread northeastward from the Gulf States. In summer, this creates a hazy, very warm and humid scene for the Northeast. Now though, the warmth is slowly drained away as the moist mild air advances over cold ground. With temperatures near the saturation point, clouds form.
If each one of us lights an inner flame for just one thing- just one aspect of our lives we are thankful for, the warmth we create can light the world on Thanksgiving. The flame of warmth and love can burn so bright that no cold wind on earth can blow it out.
One concern for later this afternoon and evening is a trailing batch of precipitation moving northeast from the Carolinas. If this survives to reach the I-95 corridor just as the cold air arrives, there could be a brief but nasty episode of snow that makes it slippery.
The exact placement of the storm center will determine who gets into the real warm air coming up on the east side of the storm and who stays in the chilly air on the west side.