Afternoon Thunderstorms For E PA/NJ/DE/MD/VA
Posted: (July 29, 2010 04:13 pm)



The map above shows the current values of surface based CAPE.  Values are currently well over what was projected with CAPE values over 2500J/Kg from the PHL metro on southward.  Current activity is very isolated, but could not rule out additional development of thunderstorms along the pre frontal trough through the next few hours.  This would mainly impact the shore points from NJ to DE if any additional activity develops.  We are tracking the potential for development of thunderstorms associated with the cold front between 1pm-7pm.  Philadelphia should be in the clear after 6pm allowing for no problems during the Phillies game.  The radar trends will give us an idea on how widespread the severe weather impact will be with this round of thunderstorms.  Over the next few hours we will be looking towards Central PA/MD/Northern VA for hints of a line of storms developing that will push eastward (IR sat already showing development).  Uni-directional wind shear is going to lead to the potential for bowing segments capable of producing damaging wind gusts.  Right now the thinking is the strongest thunderstorms will stay south of the NYC area, butt we will continue to keep you updated.    As mentioned in previous blogs, the shore points will have the best chance for active weather with a chance over the next few hours with the pre frontal trough and then again with the cold front.  Possible breaks in cloud cover can further enhance the already unstable environment also with the cold front moving through shortly after the peak heating hours.  The westerly flow in the low levels and sfc will keep the marine layer along the coast resulting in the potential for severe weather until 7pm along the shore.  Flash flooding will also be concern...especially further south with weaker flow aloft.  PWAT values are already exceeding 2" (image below).