The approach of a storm system from the west on Friday brings a slight risk of severe weather to parts of the region according to the Storm Prediction Center. They've placed a slight risk out along and west of Route 202 through Southeastern Pennsylvania -- including Allentown, Reading, Lancaster, and Pottstown on west.
This is the first piece of a one-two event that will work through between Friday and Saturday, with Saturday's thunderstorm chances perhaps a bit greater than what's on the table for Friday regionwide. However, Friday is the warmer, sunnier day of the two and affords a slightly better opportunity for severe weather thanks to temperatures in the lower and middle 80's and that extra bit of sunshine.
The first piece of energy in this one-two punch approaches the region Friday evening, with thunderstorms intensifying across Central New York and Pennsylvania.there probably will be some expansion of the slight risk area to the north into New York State as we approach the event. Since the timing for these storms is more along the lines of Friday evening and Friday night locally, the odds of severe for the city and east are going to be lower as that influence of daytime heating will be on the wane.
Gusty winds appear to be the big threat with any thunderstorms on Friday, with hail a secondary consideration. The best chances for anything severe or close to it would be to the city's northwest and west as storms would approach those areas first and still have some daytime heating to work with. It doesn't look, as of now, these storms would get into the Philly region until after 8 PM Friday evening.
A better chance for more thunderstorm activity exists for the region on Saturday with this, and a cold front back to the west, both pushing through through the course of the day.