With a warm, summery start to Labor Day weekend, the fleeting days of "summer" in the Delaware Valley will definitely remind folks of the litany of 90 degree days that ruled us over the course of July and early August. However, after Friday run into the 90's a backdoor cool front will cool off the Shore on Saturday (inland areas will still get to 90) before temperatures take a bit more of a dip into Sunday and Monday.
The front will stall to our south and serve as a boundary to allow some of Isaac's remnant moisture to track east. However, the first batch of energy may not get here until Monday. There could be some scattered showers or storms to our west on Sunday afternoon as the atmosphere becomes a bit more unstable and the frontal boundary lies nearby, agitated with the threat for a few storms in the afternoon.
However, by Monday a more substantial chance of showers and storms will be in the forecast as a piece of Isaac's energy pushes into the region and leads to scattered thunderstorms. These will be more numerous in the afternoon hours; however, there is uncertainty between the various computer models over how widespread the storms will be. The Euro features a more widespread scattering of storms across Pennsylvania and Maryland, with the Shore staying dry. The GFS features fewer thunderstorms around in number and in intensity.
It won't storm all the time on Sunday or Monday -- scattered activity looks more likely and the best chances will be west of the city as opposed to east. The Shore, for now, looks to dodge the bullet in terms of thunderstorm threats as stable air off of the Atlantic keeps enough of the storms away through Labor Day. Everyone, including the Shore, may get in on the stormy act on Tuesday as a front approaches from the west with the rest of Isaac's energy...a more widespread thunder threat will accompany the front as it passes through the region then.