Friday 9 a.m.
A low pressure area that was centered over Detroit at 8 a.m. EDT will move northeastward today. It's a storm that looks much more like a winter storm than what we often see in the summer. On the west side of the storm, gusty north to northeast winds make it feel chilly to people from Green Bay to Chicago, especially considering how hot it has been most of the summer. The air is so cool that it has interacted with the warm waters of Lake Michigan to spawn water spouts, something we predicted earlier this week.
East of the storm center, there is a southerly flow of the kind of humid air typically experienced by residents of Charleston, S.C., and Savannah, Ga. As of mid-morning, a line of heavy showers and thunderstorms stretched from east-central New York to just west of Philadelphia and thence southward to the eastern shore of the Maryland portion of Chesapeake Bay. A lesser band of showers was moving through eastern Ohio. It could evolve into a band of thunderstorms later today as it moves to central Pennsylvania... where there will be time for some surface heating to occur first.
Tomorrow looks like a pleasant, sunny day for Chicago, and it should be pretty nice all the way to western or central Pennsylvania. From northeastern Ohio or northwestern Pennsylvania into the traditional snow belts of New York state, lake-effect showers may be common tomorrow. This video has more:
This radar from just after 8 a.m. EDT shows that rain was still west of the I95 corridor in New Jersey and Pennsylvania. However, you can see why the outdoor scene can change very quickly as the band of thunderstorms moves east. Heavy rain accompanies the leading line of showers and thunderstorms.
Sam the Dog has just heard some thunder, so he wants to do what we all should do: go inside to be sheltered from an approaching storm.
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.
Jumping ahead almost two weeks, map is the 500mb flow forecast for Mothers Day. If correct, the Middle and North Atlantic states would have a sunny day with afternoon temperatures as high as the 80s! Please remember the models do best in the short range.
This map shows the pressure pattern at 9 a.m. ET. As the high moves closer and the storm moves farther away tomorrow and Wednesday, there should be an increase in sunshine with milder afternoons.
This map is the GFS forecast for when weekend rain makes its most northward advance early Sunday. The model then shows drying from north to south during the day Sunday. The ensemble mean has the northern edge in the same area. Looking ahead, it appears that warmer air is coming when May starts.