Severe thunderstorms are likely throughout the New York City metropolitan area today along with southern New England, prompting the National Weather Service to issue a Severe Thunderstorm Watch in this region through to 7pm tonight. Severe Thunderstorm Warnings are being issued for potent cells within this watch box area. The National Weather Service warns that beyond heavy downpours, the storms have the potential to produce damaging wind gusts, large hail, and isolated tornadoes.
The severe weather is marching from west to east today. Showers and thunderstorms with strong to damaging winds early in the day will be followed by a period of windy conditions after. According to the National Weather Service, a remarkably strong shortwave trough axis associated with the broad closed upper low across southeastern Canada will race quickly from near Virginia through central New Jersey by this afternoon. It is this system that is responsible for the stormy weather. At the surface, a strong cold front will race across the region developing a line of showers and storms; once the storms and rain showers pass through, a surface high pressure system will ridge in from the south and west in its wake overnight clearing out the stormy weather.
It appears the strongest storms will fire up in eastern New Jersey east of Trenton and move east toward Long Island, Hudson Valley, then southern New England eventually. Beyond large hail and isolated tornado threats, the storms greatest risk will be its damaging wind gusts: 40-50 mph winds with some isolated stronger gusts up to 60 mph are possible.
Fortunately, the severe weather threat will be relatively short lived. The front will pass quickly through the New York City metro area during the early afternoon resulting in a sharp temperature drop and sharp increase in wind speed as surface pressure rises quickly Guidance used by meteorologists suggests that west to northwesterly winds will gust in the 30-40 mph range across a large part of the northeast behind the front, with gusts around 45 mph near the coast. With a continued high wind threat, the National Weather Service has also issued a Wind Advisory where the strongest post-frontal winds are expected.
Temperatures will fall rapidly into the 30s tonight and skies will quickly become clear as high pressure builds into the Deep South and ridges into the area. A few snow showers and flurries are possible across the southern Poconos this evening, but no accumulation is expected. Some patchy frost is possible and a Frost Advisory may need to be considered for Sussex County, DE where the growing season continues through Monday. North of there, the growing season has already ended, resulting in no more need for frost or freeze warnings.