Thursday 9:30 a.m.
The dreariness of yesterday morning in the Northeast has been replaced by dazzling sunshine and deep blue skies. A fast-moving cold front will send clouds streaming across the Great Lakes then New York and New England today and tonight, then a large high pressure area from western Canada will move for the start of the weekend. You can see and hear what this high pressure area should do in this video, along with what the flow behind it should accomplish later in the weekend.
In the short burst of cold air into the eastern Great Lakes tomorrow, showers will break out in the same areas that had them last night and this morning. Since this air mass is a little colder, snow showers are likely over the higher terrain southeast of Lake Ontario. Snow showers with lightning and thunder hit the Tug Hill Plateau last night, and the same thing can happen late tonight or tomorrow morning.
Severe thunderstorms are likely to break out in the middle of the country late tomorrow and tomorrow night, then rain and thunderstorms will advance into the Great Lakes for Saturday. A switch to a southwesterly flow aloft should keep the moisture mostly north of the Middle Atlantic states for much of Sunday... but as a cold front swings around a few showers should reach the area from southern New York to Virginia on Monday.
In most of the Northeast, it is a dazzling day, with the bright sun playing off the leaves that change hue by the day. It's quite a contrast from the dull dreariness much of the region experienced the first half of the week.
This picture shows cloudiness surrounding a low pressure area off the Southeast coast. In the cloud zone, moist air rises and cools to the saturation point, and clouds form. Outside the storm, there is sinking air motion. This warms and dries the air, promoting sunshine.
A frontal zone separating cool to mild air to the north from really warm air to the south is becoming established from Illinois to New Jersey. An area of rain is moving east near and just north of the front. This map shows the setup.
Between yesterday morning and early this morning, quite a bit of lightning occurred. There can be some lightning all the way to the East Coast with this cold front, but the activity is likely to diminish. This map shows the distribution of lightning strikes in the (almost) 24-hour period ending at 7:30 ET this morning
The peak of the upcoming warmup should come on Monday for much of the Northeast. This map shows computer projections of temperatures at 4 p.m. ET Monday afternoon. Note the 80+ area in Pennsylvania. Cooler air will arrive by midweek.
As a storm slowly develops along the North Carolina coast, rain that was affecting areas of Michigan, Ohio and western Pennsylvania will tend to redevelop farther east and south. A flow from the east (see map) will keep it cool through tomorrow from New York City to Boston.
A sunny triangle is framed by a band of clouds moving southeast from Wisconsin, rain clouds over the Southeast and the western fringe of a North Atlantic storm.