Doug Simonian

Afternoon Roundup: Lingering showers, but dry air is on the way

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While not everyone in our area received heavy rain today, a decent chunk of our area did — some significantly so. A warm front and associated low pressure system brought plenty of lift and moisture, while an approaching cold front added to the lift and shifted our wind direction. This shift in wind direction from onshore to offshore allowed for coastal areas to have more instability. This allowed a thunderstorm with loud thunder and extremely heavy rain to form right near NYC and slide south into Brooklyn, where 2-3″ of rain per hour fell at times. Elsewhere, scattered showers fell — some heavy at times — but not nearly to the extent of this cell. Central New Jersey had more consistently steady rain over a long period of time, but not the same true heavy downpours. Extremely slow mid-level winds on the periphery of a ridge is why these storms were moving so slowly, and thus were able to sit in one spot and drop a lot of rain.

Over the next few hours, scattered showers and thunderstorms are still possible, with locally heavy rain possible. They will not be as dense in coverage as they were in the late-morning hours, however. The approaching cold front has allowed some dry air to infiltrate the atmosphere and the low pressure system actually somewhat stabilized the atmosphere after its initial downpours a few hours ago.

General weather highlights include:

  • Cold front will be crossing the area early this evening. Thus, the rain threat looks to end by around 7:00pm, and skies will gradually clear. Much drier air is in its wake — a true, Canadian dry airmass.
  • Winds will remain northerly and increase tonight. This will not only allow for dry air, but for much cooler air as well. Lows should drop into the mid 60s in NYC, but could fall a few degrees cooler than that in suburbs.
  • Thursday will be beautiful: sunny skies with highs in the upper 70s to around 80. Dewpoints will only be around 50, thanks to the aforementioned airmass, keeping conditions extremely comfortable. Northerly flow should also halter seabreezes as well, making it a nice beach day.
  • Thursday night may be even cooler than tonight in the suburbs, due to radiational cooling with the dry airmass and diminishing winds. Widespread upper 50s for lows are possible in suburbs. Areas closer to NYC will probably stay in the mid 60s, however.
  • Friday will be another lovely day, with temperatures slightly warmer than on Thursday — probably the low 80s.
  • Although it is early, the idea of a severe weather event is starting to gain traction for Saturday. The high pressure will be departing, as a shortwave trough moves in, providing lift, while an airmass highly supportive of severe weather will be moving in from the southwest. The NAM is forecasting CAPE values off the charts. It is still way too early to say anything definitive; though if this threat still holds traction, a more detailed article will be published tomorrow or Thursday.