For many locations in the Northeast, its looking more and more like Wednesday will be the last day we can say (with a high level of confidence) that no rain will fall in the big cities and most communities located near the coast.
While it may sound redundant, and a lot like a broken record, starting Thursday and lasting through next Monday or Tuesday, it will become increasingly harder to identify a day that will include a rain-free guarantee.
The zone of high pressure that has provided us with some nice weather, albeit cool for late in July, is going to be weakening Wednesday and Thursday nights. There is still a deep trough of low pressure in the upper atmosphere that is parked over South Central Canada and the Great Lakes region.
This feature has not only led to temperatures in these areas that are several degrees below the seasonal averages (some were no higher than the 60s Tuesday), but a series of showers and thunderstorms also blossomed Tuesday — just like they did on Monday. There should be a blend of sun and clouds Wednesday along the I-95 corridor, with interior parts of the Northeast and the mid-Atlantic states (primarily, over the higher elevations) having the best chance for getting a shower and thunderstorm this afternoon.
As the daytime heating kicks in, the atmosphere will become more unstable in those places, but the air closer to the coastal plain will still be dry enough that there shouldn’t be any rain later Wednesday.
Wednesday night, under a partly cloudy sky, it will be comfortable once again. Most outlying areas will be in the 50s, while the major cities wind up in the 60s.