If you're in the Poconos, the Lehigh Valley, or the hills in the suburban counties tonight, odds are pretty good that you'll get some light snow tonight with this weak disturbance moving through. It's not a big deal in the grand scheme of things but it is snow and for the snow starved it will whet your appetite slightly.
Precipitation this evening will be modest, with some spots not picking up much more than a few hundredths of an inch of liquid precipitation and, at most, a few spots coaxing a tenth to two tenths of an inch of liquid. It should move in after 6 PM from the southwest, quickly scooting through over a few hours of time.
The graphic below shows the general idea of where rain/snow will set up with the precipitation this evening as it begins. The rain/snow line lifts northward a bit through the evening, getting to I-78 before precipitation cuts off. If you're above I-78, you probably have a good shot at picking up an inch or two from tonight's snowfall.
We highlighted areas farther north/west of the city in our discussion yesterday on the snow as being in the best possible areas for accumulation and there are really no substantive changes from that. That said, even into the north/west edges of the city plus Southeastern Pennsylvania precipitation probably starts as snow before the transition to light rain takes place. Probably doesn't snow enough to coat the surface, however, in the immediate suburbs.
The high res model graphic (above) shows the same general idea we were speaking of in our discussion -- an inch, perhaps two for some spots in the mountains. Some conversational flakes for the suburbs and perhaps down into Mount Airy, but not a terribly big deal overall as it moves in later this evening. However, in areas where snow falls a bit longer the roads could slicken up a bit so drive a bit more carefully as you're out and about later tonight.