Thursday 10 a.m.
The moist air mass that was over the I-95 corridor yesterday has slipped offshore, and the drier air behind is promoting sunny weather. With the sunshine and a light flow from areas where it is hotter, temperatures will be heading high today through Saturday from Chicago to New York City. A strong low pressure area and cold front will come through the Great Lakes and Northeast later in the weekend. There could be some severe thunderstorms as that front advances. This video shows the basic forecast theme for the next few days.
This 24-hour lightning strike map (8 a.m. yesterday to 8 a.m. today EDT) shows the stunning boundary of the excessive heat wave that is roasting the south-central part of the country. South of the lightning zone, it's just searing sunshine with unrelenting heat. The picture probably contains the lightning strike that sent four people who were sitting under an umbrella at Wildwood, N.J., to the hospital. On a map with this scale, you can't see that one stroke, of course.
With a high pressure area over Maine, a low pressure area over western Indiana and an upper-air storm spinning over the western Great Lakes, the stage is set for wet weather in the Middle and North Atlantic states.
This map is a rainfall forecast from the NWS Middle Atlantic River Forecast Center located in State College, PA.
The upper-air flow forecast for this evening shows the trough that helps to support rainfall ahead of the cold front.
After reaching the 80s today from NYC to Boston, it might not be that warm again through much of next week.
A noticeable push of cooler air will spread southward from Ontario and Quebec into the eastern Great Lakes and New England between tomorrow and Saturday.
A cold front from eastern Canada will slide southward along the East coast between late Friday and the end of the weekend. For the area from Philadelphia to Boston, where temperatures will reach the summery 80s each day through Friday, it will mean a noticeable change to cooler weather.