Timing the Rain and the Arrival of a Low-Humidity Air Mass
Today will be another hot and humid day on Long Island with a Heat Advisory and Air Quality Alert in effect. However, there may be a sharp gradient to the humidity levels on Long Island. Yesterday, the dew points were in the mid 70's along the south shore of Suffolk, but drier air worked into northwest Nassau where dew points dropped into the low 60's, but that did come with higher temperatures in the mid to upper 90's. Once again, there is a chance of a stray thunderstorm this afternoon, but the main batch of rain is expected just after midnight with the cold front. Tomorrow should be another hot day, but with lower levels of humidity.
Saturday should see increasing clouds, but I expect any rain to hold off until at least early evening on Saturday. There looks to be a batch of potentially heavy rain for late Saturday night into early Sunday morning, although the main area of the heaviest rain may be in Connecticut. Sunday will still be cloudy and humid with a chance of showers, but the NAM model is showing that there may be a break in the rain before more rain arrives Sunday night into Monday.
There is a much drier air mass coming to Long Island for the middle of next week. Wednesday and Thursday look like perfect days with temperatures of around 80 degrees with low levels of humidity.
This image is from the NAM model at 11:00 Saturday night, and it's showing a batch of heavy rain that skims northern and eastern Long Island:
Image from tropicaltidbits.com