The slow-moving front that moved through Wednesday with thunderstorms will become a stalled, diffuse frontal boundary to our south; it will serve as a track for weak disturbances (areas of vorticity) to move near our area from west to east over the weekend.
The summer daytime heating combined with these areas of vorticity and moderately high moisture (precipitable water values about 1.5 inches) will result in instability and mostly afternoon and evening thundershowers, some which may be slow moving causing considerable downpours. Many areas will also see a fair amount of sun, especially east of the Philadelphia into NJ. Highs both days near 90.
The current GFS shows showers to our west Saturday afternoon, but significant sunshine in other areas. (see graphic)
Sunday shows more clouds but fewer areas of showers—
This sort of scenario is impossible to nail down to specifics, despite the pretty graphics; it’s presented to provide an approximation of what to expect.
What will be interesting to see is whether some showers break out around 3-4 PM today (Thursday) in Philadelphia. My view of weather models- if the short range forecast shows to be inaccurate, the longer range forecast should be taken with a grain of salt.