I-95 More Thunderstorms, I-94 a Sense of September

Tuesday morning

Violent, flooding thunderstorms ripped through much of the area between Philadelphia and New York City last evening, and the same areas could be hit again later today and this evening. The showers dwindled as they moved into eastern New England. That area is likely to receive its heaviest rain late tonight and tomorrow.

Meanwhile, cool and mostly dry air will send temperatures down to the 50s tonight from Wheeling, Illinois, to Wheeling, West Virginia. As the storms move offshore, it will turn less humid in the Middle and North Atlantic states, but the amount of cooling will be much less than was the case across the Midwest and Great Lakes.

Late this week and during the weekend, it appears that a piece of the cool upper-air trough that brought in the cooler weather will break off from the main upper air current. Once that happens, the disturbance can mill around for days, causing clouds and spotty showers in seemingly random places. At the same time, the main current will run from the central and northern Rockies all the way to south-central Canada, warming up that area quite a bit. By Saturday, daytime temperatures at Bismarck, North Dakota, will be soaring into the 90s while places like Pittsburgh and Philadelphia have readings almost 10 degrees lower.

This video has the forecast through the weekend as well of a time-lapse movie showing a squall line arriving at my house in central Pennsylvania on Sunday evening.

This map shows the scenario of hot air spreading across the northern Plains and north of the Great Lakes, while a pocket of cool air aloft gets stranded over the Middle Atlantic region.