With an approaching cool front coming in from the west slowing as it crosses the region, we'll see some showers and steadier rains in the offing tomorrow and tomorrow night as a wave of low pressure rides northeast along this slowing frontal boundary. The vast majority of computer guidance out there is suggesting that the region should see rainfall from late in the afternoon tomorrow into the overnight hours before the rain ends towards daybreak.
The good news for us is that rainfall locally does not look like a huge factor. Modeling from the GFS, NAM, Euro, and other higher resolution models paints the rainiest locations to our west and northwest -- generally Central and Northern Pennsylvania look to pick up the most rainfall from tomorrow night's setup, with steadily lower rainfall totals as one works southeast towards the coast.
Using the NAM as an example, most of us should see only a couple of tenths of an inch of rain out of tomorrow night, with the Poconos and Lehigh Valley getting over a quarter inch of rain. Heavier rains -- the over one inch variety -- would occur across Central, Northern, and Western Pennsylvania. Rainfall around the region looks to be particularly modest as the bulk of energy and dynamics with the surface low track away from us.
Any rain that does fall on Thursday evening should exit the region in time for Friday morning's rush hour, yielding a nice Friday in the Delaware Valley, albeit without 70+ degree weather.