June 1, 2013: Storms Return Sunday Night, Monday

Forecast Highlights:

A heat wave continued across the region, with temperatures again in the upper 80s to low 90s across most of the area. A strong cold front will affect the region on Sunday into Monday, bringing an end to the heat wave while producing strong thunderstorms on Sunday evening and night, mostly north and west of NYC. Once rain clears the area on Monday, several days of sunshine and generally seasonable temperatures are expected before rain and humidity return by the end of the week.

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Tonight - Monday: Heavy Storms Expected

A low pressure in the Midwest that has been responsible for the recent severe weather outbreak in the central US will continue to track northeast into Canada, with its cold front gradually tracking east, slowly moving through the area on Sunday night into Monday, producing widespread thunderstorms across the region while removing the warm air mass that has been in place for the last few days. Sunday is expected to start out partly sunny with gradually increasing cloud cover, with highs peaking in the upper 70s to low 80s in the coast and the mid 80s to 90 degrees across the rest of the area.

With moderate instability ahead of the approaching cold front, scattered thunderstorms, some of them severe with strong wind gusts and hail, are expected to develop in PA and NY states, primarily north and west of the area, on Sunday afternoon. The relatively slow timing of the cold front will favor locations north and west of the area for the highest risk of severe weather, with the strong storms shifting into NW NJ and SE NY by the late afternoon hours, reaching the immediate NYC area around 7-9 PM and locations further east by at least 11 PM-1 AM. The risk of severe weather near NYC will be lower, although storms will still be capable of producing strong wind gusts. With high precipitable water values and the overall slow motion of the front, storms will be capable of producing heavy rainfall with localized flash flooding. Occasional thunderstorms will continue overnight, with showers expected to continue into the first half of Monday as well with cooler highs, back into the low to mid 70s across most of the area. Overall rain totals are generally expected to end up between 1/2 and 1 inch, with locally higher totals up to/over 1-2 inches north/west of NYC and locally lower totals mostly east of NYC.


Tuesday - Next Weekend: Sunny And Dry, Then Humidity Returns

As the cold front exits, a trough will set up over the region with a high pressure building in from the northwest providing sunshine and temperatures slightly cooler than average, peaking in the low to mid 70s across the area on Tuesday and Wednesday. Chilly temperatures are expected overnight, falling into the mid to upper 40s inland and the low to mid 50s for the rest of the area.

By the late week into next weekend, ridging will return into the region with an expected SSW-SW flow aloft, spreading a more humid air mass into the region. The model guidance shows differences with the handling of this set up, as well as a low pressure originating in the Gulf of Mexico and tracking into the Southeast US; some of the models bring this system up the coast, producing widespread rain and thunderstorms along with increased humidity for Friday and most of the weekend, while others take the low offshore with a drier weekend. There is uncertainty regarding the specifics in the weekend outlook, although the overall expectation is for potential rain and thunderstorms on Friday and most of the weekend along with more humid conditions. Stay tuned for more information on the longer range outlook.