The theme of the next several days is for scattered showers...odds favor the afternoon and early evening featuring more showers popping up thanks to atmospheric instability and daytime heating but in reality a shower can't be ruled out any time thanks to the persistent nature of upper level energy that's across the Northeast. This low is part of the same system that moved through the region on Friday night with the rain and severe weather. The upper level energy broke off from the storm system as it moved through and has slowly meandered across the Great Lakes and now over the Northeast.
It won't shower constantly each day -- but like Sunday and Monday, there will be periods of time where the weather will be less-than-ideal and off and on rounds of showers around the region. Given that there is little in the way of a jet stream to move this system along, we're stuck with it for the next several days for the most part. The upper low will have various little disturbances spinning around the main vortex over the next several days -- with Wednesday the likely next "active" period across the Delaware Valley where showers could be pretty widespread in the afternoon.
The upper low gradually opens up into a trough and slowly pulls away by Friday, leaving us just a chance of a few showers around in the afternoon as high pressure builds in from the west.