Tuesday 7 a.m.
A low pressure area drifting slowly northeastward from North Carolina is causing bands of rain, some heavy with embedded thunderstorms, to its north. This rain will slowly spread to Pennsylvania and New Jersey later today and tonight, then farther north tomorrow and tomorrow night. Anytime there is a banded structure to the precipitation and highly varying rainfall rates, chances are there will be quite a lot of variation in the rainfall amounts received from one place to another.
As the low pressure area departs, there is no strong high pressure system coming in to replace it. Some moisture will linger, and this can lead to varying sky conditions and even a few showers.
A strong cold front will cross the Great Lakes Saturday and reach the East Coast on Sunday. This front can trigger one or more lines of showers and thunderstorms. After that front goes through, a strong northwesterly flow of much cooler air will take over. Downwind from the Great Lakes, some showers can break out, and it'll be so chilly some residents will think it's going to snow (and over the highest terrain it could!). Our concern with the new air mass will be the potential for a frost or freeze. I suspect that city gardens from Chicago to New York City will be okay, but if you live at a normally colder location, you might want to resist the rush to plant annuals.
Today's Northeast video
This video concentrates on Chicago but could also be useful if you're in Detroit, Milwaukee or any other place around the Great Lakes:
The Middle Atlantic storm has a history of causing thunderstorms. This map shows the lightning strokes from the middle of last night through early this 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.
This is a satellite picture showing rather tame conditions off the South Atlantic coast at 7:45 AM ET today. The area is being watched for any signs of storm development.
When looked at this way, you can see two distinct flows in the East: one from the south with moisture, and one from the west that is dry. There is a problem, however: the model solutions evolve over time, and as we get closer to next Monday afternoon (the time the forecast maps are using), the lines and orientations will probably change.
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