Some computer modeling is suggesting the possibility of a band of heavier rain and thunder tomorrow afternoon across Pennsylvania as the next slow moving front approaches us from the west. Modeling is not sold on placement/timing/detail of where rain and thunder set up but they do show the potential for at least a stronger line of showers and thunderstorms across portions of Eastern and Central Pennsylvania during Tuesday.
The NAM (below) is arguably the most aggressive in bring the front into the region, with the band of rain setting up across the western suburbs by dinner time tomorrow evening. Other modeling (GFS, EURO) place the band a bit farther to the west and allow the Delaware Valley to remain dry into the evening hours.
At this point, no risk for severe weather is in the forecast -- Central Pennsylvania is in a "see text" area tomorrow from the Storm Prediction Center which means an isolated severe storm can't be ruled out but odds are against it happening. That said, a few of the thunderstorms that do develop could dump some pretty heavy rainfall and bring some gusty winds along for the ride.
Some computer model estimates by Wednesday morning paint the potential for up to two inches of rain across Central Pennsylvania (generally north of Harrisburg on to the west), with a half inch plus possible from Philly on west and north. Since the front will be slow to move, South Jersey may stay dry through Tuesday night before getting in on the fun Wednesday as the front slides through.