A weak backdoor cold front will continue to sag slowly south this evening. This front will continue to move south on Sunday. Showers and thunderstorms could develop at any moment around the boundary, but the coverage should be isolated. MOS guidance indicates lower nineties for Philadelphia while New York City will be in the middle eighties. I am a bit worried that the MOS numbers are a bit on the high side with a developing north wind behind the front on Sunday.
A strong cold front with the potential for area of low pressure to ride along it will be the issue for Tuesday into Thursday. Some models want to drop a quick one to three inches of rain from this system over the course of the three days. Most of the model guidance is optimistic that Thursday will be drier than Tuesday and Wednesday with the front moving along steadily, but one outlier model keeps Thursday fairly wet as it puts the breaks on the front and allows it to tap into moisture to our south. However, much of the model guidance keeps at least little spokes of energy in and around the area into the weekend which requires at least isolated/slight chance mentions of thunderstorms or showers.