Showers, Mainly South?

Showers may spread in late tonight, especially south of the city, but periods of rain are more likely on Friday from Philadelphia on south as a disturbance tracks east along a stalled frontal boundary that lies to our south. The challenge for forecasters and computer modeling is determining how far north that rain shield gets -- the NAM, for example, essentially shuts the rain shield off at Philadelphia and along 422 to the northwest, with increasing totals of rain to the city's south.  Some parts of the Delmarva may pick up over a half inch from this event -- it's just a question of how far north the northern extent gets.   The NAM is the most south of that extent, with the GFS and EURO painting rain farther to the north...perhaps even into the Poconos.

The high resolution modeling from the Storm Prediction Center shows the potential for some rain on Friday evening across Pennsylvania.   During Friday, most of the rain stays south of the city across Delaware but by dinner time the chances for some precipitation near Philadelphia increases.  It is in the "southern" camp to an extent but does suggest that the northern blob of rain in Pennsylvania could track through Friday evening and overnight.

Regardless, the best chances for the most rain are south of the city, with areas north of Philadelphia on the fence to get little more than just showers.  In fact, it could be dry if the NAM is right outright.

We'll update the weather outlook in the morning.