Our warm pattern in place holds into Thursday before we run the risk of a backdoor front pushing in off of the Atlantic at some point during the day. It's still an uncertain prediction because the higher resolution models are waffling around on timing and strength of this feature but it does look like the prospect for some natural air conditioning off of the Atlantic is a possibility for portions of the area later in the day Thursday into Thursday night.
With such a front, winds veer around from west to east, off of the Atlantic, resulting in cooler air flooding inland and temperatures dropping off.
Yesterday's midday run of the NAM was much more pronounced with the front -- having it into Philadelphia by midday and down south of Wilmington by 5 PM Thursday. Before the front, temperatures were poised to get into the 70's in the city, with 50's around town by 5 PM based on yesterday's model run.
This morning's run of the NAM is a bit less aggressive with the backdoor front, showing it still north of Philadelphia by 5 PM, with 70's across much of the region except for the northeastern half of New Jersey. Yesterday's runs of the Euro showed a similar evolution -- from a cooler solution in the afternoon to a warmer one in this morning's run where the timing of the front is delayed a bit.
Regardless, Thursday won't be a chilly day by any stretch going out the door as temperatures will likely be at or above 60 in many spots to start the morning...but northeast of the city it may be getting markedly cooler by day's end as winds fire up off of the ocean and it may be cooler Thursday evening in Trenton, Belmar, and points north than it was in the morning hours. We may end up coaxing 80 out of Thursday when all is said and done in the city, with the backdoor front shooting through during the evening hours, perhaps timed with the start of rain that will linger into Friday, which will result in a much cooler Friday (or at least a cooler start to Friday) around the region.