8:46 PM

This morning I was preparing for an active afternoon of severe weather for the Delaware River Valley and eastern Pennsylvania with the potential for strong thunderstorms for the rest of the region.  While thunderstorms did organize and push towards severe levels over much of eastern Pennsylvania, the thunderstorms weakened as they moved towards New Jersey.  The strongest thunderstorms have been and continue to be located over Maryland, Delaware, and eastern Virginia.  So what prevented the thunderstorms from entering New Jersey and points east?

In the morning discussions and at the start of the “twitter” updates, I discussed that the clearing of low clouds that were present this morning along the coastal plain was going to be key in determining if severe weather would develop.  As the morning storms continued to press into the Atlantic, low clouds and showers continued to linger behind the exiting warm front.  This was due to the stubburn marine air mass hanging around at the surface through 950 MB.  As a result, clouds were slow to clear and the atmosphere did not destabilize to the full potential that was present.  However, over much of eastern Pennsylvania, the skies cleared, the temperatures jumped into the mid 70′s to mid 80′s for afternoon highs, and the atmosphere become unstable.  The result, strong to severe thunderstorms.  So in short, the fact that the strong thunderstorms, which produced very heavy rainfall by the way, moved through the coastal plain basically limited the potential for strong thunderstorms in the afternoon.  

Most locations will get a break from the precipitation tomorrow as weak high pressure ridges into the forecast area from the Great Lakes.  The cold front will stall south of New Jersey, however a few showers will still be a threat in the afternoon hours.  A strong low pressure will drive towards the Great Lakes on Wednesday night and Thursday.  As a result, a warm front will drive north on late Wednesday night with a few showers followed by a strong cold front on Thursday with the potential for strong to severe thunderstorms once again.  The set up appears to be very similar to what transpired today with the potential for severe weather influenced by the speed of the warm front and ability for the atmosphere to destabilize.  

There will remain a threat for showers and thunderstorms through next weekend as the cold front stalls south of the forecast area.  The highest threat for showers and thunderstorms will be over southern New Jersey through this weekend and there is potential for most locations to remain dry with high pressure not far away over western and northern New York.