Friday 10 a.m.
Steamy, sultry air is in place from southern New England and the Middle Atlantic states through the Ohio Valley and southern parts of Wisconsin and Michigan. The air mass is destabilizing a bit in New York and Pennsylvania today, and some models predict that thunderstorms will break out. This can happen again tomorrow afternoon. In some situations, the location of one day's storms can give hints for the next day. Thunderstorm rain cools the ground and the outflow from each storm reaches a certain point before stalling. The boundaries set up in this manner can serve as the starting locations for storms the next day.
A cold front advancing eastward from the northern Plains will come through the Northeast late Sunday and Sunday night. It may trigger violent thunderstorms, so it would be a good idea to keep track of any storms on your mobile device to see if there is an immediate threat at your location. Tropical Storm Ernesto does not look like it will have any direct effect on the Northeast. Here is today's video:
This pressure analysis shows a frontal boundary extending from north of Lake Ontario to southeastern Wisconsin. Some showers have formed near that boundary this morning. The front will move southeast through New England this afternoon and cause some thunderstorms. The front will move back north tomorrow.
This map shows the pressure analysis for the Northeast and Great Lakes. The gusty flow on the west side of the low pressure area adds a real autumn feel to the air.
Since individual lines and clusters of thunderstorms have limited life spans and change character constantly, forecasting whether it will or won't rain at any one time this weekend is difficult at best. One solution is to have your tablet or phone available with the AccuWeather.com app so you can see where all the storms are at the times when it concerns you the most.
It does look warmer for the weekend, but every time the warm air tries to extend into New England it gets chopped down. There could be more showers at times Sunday and early next week as forest we can tell. If any forecast gives you a headache, why not take a friend's advice: Take two aspen; sequoia in the morning.
This map from 5AM ET shows the cold front that is continuing toward this Northeast and Middle Atlantic states. Temperatures stayed up in the 70s all night ahead of the front but it turned noticeably cooler after the front moved through.
The cold front that will cut off the heat will generate strong gusty thunderstorms as it moves southeastward today. The National Weather Service Storm Prediction Center highlights the most likely area for these severe thunderstorms today and tonight.
As the high pressure area in the Northeast moves away, the the southwesterly flow pattern will shift eastward. This means Wednesday could be the hottest day of the week from D.C. to Boston. A cold front will follow.