The overall weather pattern features an energetic, undulating jet stream and a lack of blocking. Since individual storms are becoming strong, they are capable of tapping very mild air from the south as they approach and very cold air from the Arctic as they move by.
Today, with a strong storm off the East Coast, a blast of cold air is pouring south on its western side. On Sunday, with a strengthening storm moving through the Great Lakes region, south winds will be pulling mild air back into the East. Temperatures could be in the 40s late Sunday from Boston to Philadelphia. As the storm departs, an air mass that rivals or exceeds the current one in terms of coldness will rush through the Great Lakes then "polarize" the Northeast. This video has more:
This pressure analysis shows that with a powerful storm offshore, cold air has an express route right down along the Eastern Seaboard. Note the southerly flow in the middle of the country.
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