NY NJ PA Weather Forecasts

Active weather pattern continues for this week

7:28 AM

The weather pattern for this summer certainly is developing an active characteristic as yet another week of persistent threats of showers and thunderstorms can be expected. 

There are a lot of interesting features to examine on the water vapor this morning, so lets dive right in!  A trough over the Canadian Maritimes continues to slowly lift to the northeast, however the orientation of the trough this morning is supporting a weak cold front over northern Pennsylvania cutting through the New York City metro.  The convergent pattern over Ontario is support Canadian High pressure, which forced the cold front south through early this morning.  However, a strong upper level disturbance and surface low over the Plains this morning is gaining influence on much of the Eastern United States this morning.  The Plains disturbance is producing a strong MCS over the Great Lakes and Mid West this morning and is starting to draw moisture from the Gulf of Mexico and off the Southeast coast.  

Through today, the old cold front boundary will lift northward as a warm front, which will put the entire forecast area in a warm, moist, and unstable air mass by this afternoon.  Now in most cases, an easterly wind will bring a stable marine air mass into the forecast area.  However, in this case, due to the tropical moisture lifting northward along the East coast, a more unstable air mass can be expected.  A few mid level disturbance will move along the warm front and through the warm air mass this afternoon.  These disturbances will be the remnants of the MCS that has formed this morning.  Think of them like waning echoes that will travel eastward.  These disturbance will spark off a few showers and thunderstorms, especially over the Delaware River Valley.  Given the warm, moist unstable nature of the atmosphere and a developing 850 MB jet stream, the most significant threat from the thunderstorms will be strong wind gusts over 50 mph and large hail.  However, I think the threat for thunderstorms pushing to severe levels will be isolated.

The low pressure system over the Plains will drive towards the St. Lawrence River Valley on Tuesday afternoon with a trailing cold front cutting through the Mid Atlantic in the afternoon.  With a warm, unstable, and moist air mass in place already; the strong PVA associated with the cold front will have no trouble supporting strong to severe thunderstorms, especially in the afternoon.  Once again, the best potential for strong to severe thunderstorms will fall over the Delaware River Valley.  The directional wind shear will be weak, so I don’t expect any tornadic thunderstorms, however the speed shear will be present and thus strong wind gusts from these thunderstorms can be expected.  Wind gusts exceeding 55 mph will be possible in the strongest thunderstorms while cool, dry air at 500 MB will support the potential for small to large hail production.  However, the greatest threat from these thunderstorms will be the very heavy downpours.  If more tropical moisture off the East coast gets involved, the heavy downpours will be tropical-like which means rapidly reduce visibility and potential for flash flooding.  Sounds like a fun afternoon!

The cold front will clear the coast by Wednesday morning as weakening high pressure from the Great Lakes will move towards the Mid Atlantic.  Clearing skies and lower humidity can be expected, briefly on Wednesday morning.  However, as the high pressure quickly exits, winds will back to the south and southwest, which will bring a humid, warm, and unstable air mass in from the Tennessee Valley by Wednesday afternoon through Thursday morning.

Another strong area of low pressure and impressive cold front will move through the region on Thursday with showers and thunderstorms.  The timing of the cold front will naturally be an issue in terms of potential severe weather.  The best upper level dynamics will be found over New England, however strong PVA will be present along with increasing speed and directional wind shear.  These factors all point to another potential for strong to severe thunderstorms on Thursday afternoon and evening.  

High pressure from the Great Lakes and Mid West will move towards the Mid Atlantic on Friday with clearing skies and much lower humidity.  High pressure will remain in control through Saturday with pleasant conditions, however the cold front boundary that moved through on Thursday will have stalled over the southern Mid Atlantic back through the mid Mississippi Valley.  A weak low pressure system will develop along this cold front and quickly move towards the Mid Atlantic coast on Sunday.  The majority of the precipitation will be focused over Virginia and Maryland, however the potential for showers will be present on Sunday as the low pressure system exits.  The introduction of moisture from the tropical disturbance over the western Caribbean will have to be monitored as this disturbance could allow for an expansion of the precipitation shield and thus a wetter forecast than currently anticipated. 

Temperatures through the period will average near normal.

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