Thursday 10 a.m.
The high pressure area marking the center of the chilly air mass that is now over the Great Lakes and Northeast will move eastward and will be offshore tomorrow night. The ensuing warm-up occurs in two stages. First, there is an increase in sunshine with a decrease in wind. This makes it more comfortable.
Then, a southwesterly flow gets under way. That flow extracts the last of the chilly air and allows warm air to assume control. When fully in place, the warm air mass will be capable of sending temperatures toward 90 if there is full sunshine. We expect temperatures to reach or surpass 80 degrees from Virginia to near New York City.
Meanwhile, locally violent thunderstorms will cross the Plains. Please see our severe weather reports and numerous news items as this situation develops. By Monday, the northern end of the cold front that sponsors the thunderstorms will move to northern New England.
The question then becomes how far south the front will progress. Behind the front, it will turn chilly, and with a cold high pressure area moving into eastern Canada, a chilly northeasterly flow is likely to advance down the coast through at least most or all of New England. These fronts usually move the farthest south when the ridge axis aloft is west of the Eastern Seaboard. The computer models for early next week suggest that will not be the case in the coming setup. This video has more.
In central Pennsylvania, yesterday was March-like and it snowed for a while at many spots. In response to cold air aloft and temporary heating at ground level, large cumulus clouds towered into the sky and a series of showers/snow showers developed. This picture was taken a few minutes before one of these showers arrived.
Labor Day is a week from Monday. The computer model used here, the GFS ensemble mean, suggests the weather will favor outdoor late summer activities across the Great Lakes and Northeast:
In response to heating at ground level and a weak cold front approaching from the west, showers and locally strong thunderstorms should develop across northern Ohio this afternoon.
... much greater interest is being generated on threats and rumors about tropical storms. It is worthwhile to read Dan Kottlowski's authoritative reports on this. Here is a copy of his map from this morning:
The tropical Atlantic shows signs of life in the storm development department. Dan Kottlowski's expert discussion suggests the third storm (which could be Hermine) of current concern is one that could head to the Bahamas, Florida, the Gulf or ???
A large high pressure area centered just south of Chicago will furnish a northwesterly of pleasantly cool and dry air to the eastern Great Lakes and all of the Northeast today into Tuesday.
As the trough moves through each locality, warm humid weather will be followed by showers and thunderstorms, then cooler an drier air will arrive