The GFS model has been consistently predicting low pressure to approach our area from the southwest and bring heavy rain to PHL for Saturday, as a coastal low forms over the Delmarva area.   (For the record, the European Model had it moving south and missing us until recently.)

Saturday will be cloudy with rain, fairly heavy, beginning about 8-9 AM and continuing through the day. High 63.

An upper cyclonic flow over our area on Sunday, with an area of vorticity rotating through during the day will keep mostly cloudy skies for most of Sunday (maybe some bright spots) with a persistent chance of scattered showers, especially during the afternoon.  (Any sunshine will be of the self-destructive form, due to instability.)  High 67.

10pm update:  latest NAM has most of the rain holding off until afternoon on Saturday.