Friday 10:40 a.m.
Chilly air is advancing into the Northeast this afternoon, and in many locations, tonight's chill will rival all-time records for the date. That's because the high pressure area marking the center of the chilly air mass will be right over the I95 corridor tomorrow morning, causing clear and calm conditions. Then, once the high moves to the east, a south to southwest flow of warmer air will become established. By Sunday afternoon, temperatures will be in the 60s throughout southern New England and 70 or higher farther south.
Strong thunderstorms from the middle of the country will head toward the western Great Lakes. The severe weather section at accuweather.com can be very helpful in explaining how these storms may affect you.
Tomorrow morning will be chilly in the Middle and North Atlantic states. Sam The Dog seems to like his early trip outside on cold mornings. I think it makes him appreciate the great usefulness of his fur coat.
For example, the purple line in the east marks the boundary between air coming in from the ocean and a southwesterly current of warmer air. That boundary was the scene of showers and thunderstorms when it was in the middle of Pennsylvania yesterday, and was associated with rain that moved through the Hudson Valley early this morning.
Looking ahead to late next week, some of the computer models suggest a hurricane could affect areas between the Gulf of Mexico and the Atlantic east of the Bahamas. We are entering the prime part of the Atlantic hurricane season, but at this point there is only one model I am prepared to accept:
The following map shows the individual members of the forecast for the 5,880-meter height line at 500mb. If the 500 mb height is that high, it usually means the weather at the ground in the Northeast is hot. However...
This pressure analysis was made using 9 a.m. ET data. The thin west-east black line is the boundary between hot and cool weather. A low pressure area is moving eastward along the boundary zone, causing showers and thunderstorms. The next low pressure area should send some of the rain farther north.
In the early to middle parts of next week, we expect to see a boundary zone separating hot, humid air to the south from cooler air to the north. A series of ripples or disturbances aloft moving west to east will take turns at enhancing or reducing the chance of showers and thunderstorms.
Looking beyond next week, we see signs of something that has been missing in the Great Lakes and Northeast just about all summer: hot weather. That may change. Here is a computer model prediction of the upper air flow on Sunday, Aug. 24. Note how the flow appears to run from Arizona all the way to north of New England.