The end of the heat wave is in sight, with Saturday marking the day where thunderstorms and a cool front should approach the region and produce the beginnings of relief that will result in gradually lower high temperatures starting Sunday.
We're under a slight risk for severe storms across most of the region on Saturday -- the exceptions now reside south of the city and that's mainly due to the expected timing of thunderstorms across the region. It appears that most of the thunder threat resides in the afternoon and evening hours, sliding from north to south as storms fire and slide on south through the course of the day. Modeling varies on specifics on location/timing but it appears that the highest risk of severe weather will be across Central into Northeast Pennsylvania, east into North Jersey and Southeast and Eastern New York.
Speaking of modeling specifics, here's a picture of the NAM from this morning for Saturday around 2 PM. There'll be some changes on the specifics but you can see the cold front outlined pretty well to our north, generally along and above I-80 by this point in the day. There could be some thunderstorm activity that tries to fire up ahead of the front -- the GFS also hints at this to an extent -- and if something like that were to occur we could see some of the early PM thunder zap the atmosphere of potential juice for the main line of activity that slides southeast in the afternoon.
If the earlier thunder threat does not materialize, it looks like we should see the line of storms with the front slide into the northern suburbs and Lehigh Valley after 5 PM, into the city around or just after 7 PM.
The primary threat with this possible severe weather setup would be wind and downbursts, which is a typical setup with heat wave ending storms as the atmosphere tends to be a bit warm aloft to support much in the way of hail. That said, hail can't be completely ruled out but it looks to be more of a damaging wind possibility for some locations (especially northwest of the city). Some heavy downpours can't be ruled out either, with the best chances of those also to the northwest of the city.