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.
More than 110,000 lightning strikes occurred in the northeast third of the nation in the 24 hours ending at 11 a.m. EDT today (June 13).
This map shows the low pressure at the western edge. The isobars help define the location of the frontal boundary between the hot and cool air masses.
This map shows the area that could have damaging thunderstorms tomorrow and tomorrow night.
The Northeast regional radar at 10 AM showed a large area affected by showers and thunderstorms:
Whereas Andrea was centered in eastern South Carolina at 8 a.m., this satellite water vapor image shows the greatest concentration of moisture is well northeast of the surface circulation center
Quite a few models are in use, and this map shows there is widespread agreement on where the center of this storm is going.