NY NJ PA Weather Forecasts

Increasing severe threat for forecast area this afternoon

7:46 AM

A very active period of severe weather looks to be developing for much of the forecast area this afternoon.  The entire forecast area is under the influence of a warm, moist air mass.  Already this morning, a few showers and thunderstorms have developed over easterly Pennsylvania and will move towards the coast through the morning hours.  These showers and thunderstorms are associated with a weak surface trough and mid level disturbance.  

The ingredients for severe weather will come to a head later this afternoon through the evening hours.  Once the showers and thunderstorms exit the forecast area by late in the morning, breaks in the clouds will allow the warm June sun to heat the lower levels of the atmosphere.  Temperatures will quickly jump through the 80’s and lower 90’s by this afternoon.  As for moisture content, dew points are already in the mid to upper 60’s and will have the potential to  push to around 70 degrees ahead of the advancing cold front.  This means that the atmosphere has plenty of moisture available for thunderstorm development ahead of the advancing cold front.

However, the key for severe weather is not just the warm, moist lower levels; but the advancing cold, dry air at the upper levels.  Note the dry air over central Pennsylvania this morning.  As the trough, which currently is positioned over the eastern Great Lakes, moves towards the coast; the cold, dry air will interact with the warm, moist air at the surface.  The atmosphere will continue to rapidly destabilize and support the development of strong to severe thunderstorms.  The fact that the air aloft is much colder and drier is key for this afternoon.  The dry, cool air will support the development of a pool of rain-cooled air within the thunderstorms.  When this occurs, the air will rapidly sink towards the surface, which leads to very strong wind gusts and significant wind damage.  Another risk with the cold air aloft is the potential for large hail to develop within these thunderstorms.  Finally, there is some indication of some directional wind shear this morning over the Delaware River Valley through the southern Hudson Valley, which would support an isolated super-cell or tornadic thunderstorm.  However, the most prevalent threats for this afternoon and evening will be the strong wind gusts, very heavy downpours, frequent lightning strikes, and large hail.  These thunderstorms will be capable of  flash flooding of urban locations and around small streams and rivers.  Rainfall rates of 1 to 3 inches per hour are not out of the question with these thunderstorms.  These thunderstorms will potentially impact the game times and conditions for the Mets/Yankees game at Citi Field in Queens, New York.

The cold front will exit the forecast area by tonight, however the upper level trough will remain over the Northeast and Mid Atlantic through the weekend.  Several weak disturbances will move through the region on Saturday and Sunday and bring a risk for showers and thunderstorms each afternoon.  Not all locations will be impacted by these showers and thunderstorms, however where these thunderstorms do develop, those locations will be significantly impacted.  The thunderstorms on Saturday and Sunday afternoons will have characteristics that will support flash flooding, frequent lightning, very strong wind gusts, and large hail.  The reason for this potential is the cold air aloft, which will support the environment for these features.  These thunderstorms are most likely to develop over the Poconos, northwestern New Jersey, the Hudson Valley, and central Connecticut.  

As one trough exits and weakens on Sunday, another trough and upper low will approach from the Great Lakes.  Doesn’t this sound familiar?  The trough will remain over the Northeast and Mid Atlantic through all of next week.  Several disturbances will rotate through the region and bring a risk for showers and thunderstorms each day at various times of the day.  The forecast area will be on the eastern side of the trough through the week, which will put the region in the warm sector of these disturbances.  Temperatures will generally remain in the lower to mid 80’s for highs, which is near normal while dew points will remain in the mid 60’s; which will produce warm, humid conditions through the week.

Tags: Albany, Allentown, Atlantic City, atlantic ocean, Belmar, Bridgeport, Citi Field, coastal waters, Connecticut, Freehold, hail, Hartford, heavy rain, Islip, lightning, Long Island, Long Island Sound, Mets, New Jersey, New Jersey coast, New York, New York City, Newark, Pennsylvania, Philadelphia, Phillies, Poughkeepsie, Reading, Scranton, Sussex, thunderstorms, tides, tornado, White Plains, Wild Wood, Yankee Stadium, Yankees