Today we have a cold front and a dip in the jet stream approaching from the west, this will lead to scattered to widespread showers and thunderstorms, especially this afternoon under partly to mostly cloudy skies and temperatures in the upper 70s to id 80s with very high levels of humidity , the highest threat with these showers and storms will be very heavy, tropical like downpours which could lead to localized flash flooding , the severe threat with this set up is not very high given the tropical air mass at basically all levels from the surface up to 700 mb , and not much in the way of the colder drier air aloft to trigger those strong storms and with so much cloud cover in place there may not even be much in the way of development of storms this afternoon, we will have to wait and see.
With the large western Atlantic ridge in place we can see the trough is beginning to stall , and should stall over or just west of the forecast area , and with some interaction with the remains of Tropical storm Chantal ,will lead to isolated to scattered showers and storms from Friday through Monday , certainly will not be a washout, as a matter of fact it should be partly cloudy for the most part this weekend just have to watch the sky for quickly changing conditions with any isolated activity that may impact , temperatures will be near normal with modest humidity. Highs will be in the upper 70s for NE PA, lower to mid 80s elsewhere and lows in the low to mid 60s NE PA to mid 60s to around 70 elsewhere , highest threat with any storm will again be heavy tropical downpours and gusty winds.
By Tuesday the trough will lift north and east , the frontal boundary will likely weaken and dissipate as we see a heat ridge currently over the Plains, extend eastward and merge with the persistent and strong Atlantic ridge, I expect we will see another prolonged heat wave starting Tuesday and lasting through the extended period with widespread 90+ degree temperatures and modest to high humidity
There is full model agreement on a large ridge developing over the eastern US and really much of the US as a whole , this could prove to be a somewhat unsettled pattern for the eastern US with a trough trying to linger over eastern Canada , interacting with the building ridge we could see some MCS complexes, especially north of the forecast area , this will come down to placement and strength of the ridge, and whether we end up on the Northern fringes of it.
One thing that is certain is after a brief break this weekend the heat will come back and likely come back in a big way , and it appears to be a very slow-moving to stagnant weather pattern so it will likely stick around for a while.