Tuesday 10 a.m.
Extremely moist air remains in place from Florida to Maine, and there are areas of showers and thunderstorms scattered through this zone. The activity typically peaks in the afternoon hours and wanes at night. Be ready for locally flooding downpours, realizing however that most places will have long periods of rain-free weather.
There are two different temperature regimes today: cool air across the Great Lakes region and very warm steamy air to the south and east. This map shows the dividing lines between these zones from early this morning.
During the next few days, the high pressure area off the East coast is likely to expand westward. This will involve warming aloft and should lessen the amount of thunderstorms. The cool air should gradually erode across the Great Lakes region, promoting some sunshine and higher temperatures later in the week. These changes are a bit subtle and the effects will not be uniform, so check back with us for the latest forecasts as we go into the holiday weekend.
Tropical Storm Colin is caught in the southern stream while the northern stream is helping to send unseasonably cool air out of central Canada.
Then, as the cold front arrives, there may be violent thunderstorms. This map shows the early morning SPC assessment of the severe weather risk on Sunday:
Farther east on Sunday, rain is likely to be more extensive, and there is a severe thunderstorm threat from the Middle Atlantic region on south.
With the second front, shower activity may be spotty at first as the system comes through Chicago on Saturday but could be wetter and more stormy than the first front by time it reaches the I-95 corridor Sunday.
A pocket of dry air covers most of the area from the Great Lakes to the back edge of the East Coast clouds. This suggests sunshine will be the rule across the Northeast until the next frontal system approaches later in the week.
Here is the severe weather outlook for today from the NWS Storm Prediction Center. Note at the bottom the population in each alert area is listed. Keep in mind that in any given severe weather situation, the number of individuals directly affected is far less than the number of people potentially threatened.