It was a great, yet somewhat unexpected storm here. In the days leading up to Sunday the SPC (Storm Prediction Center) had their eye on the potential for a narrow band of convective storms to develop. Mainly to the north of and at the triple point of an upper level low that was to pass by. As the day got closer we were put into a "slight" risk, and then dropped a few times (citing the marine layer would take over) before being upgraded once more during the day on Sunday with a 2% chance of a (isolated) tornado, and a 15% chance of hail. It was a tricky forecast because it all depended on where the warm wedge of air was able to make progress to. The National Weather Service opted to not even issue watches, as the setup had to be perfect. As Boyd pointed out though, South Jersey had no problem reaching the 70s as a warm front pushed north sending dew points into the 60s with clearing skies and setting the stage for a severe outbreak. North Jersey at this time was still in the 40s and 50s with low clouds, being north of the front. As the day went on there was increased lift which aided to the development of a line of storms, to the NW over Adams, York, and Lancaster counties. This was the triple point where we saw an explosive development of storms which quickly raced northeastward as a warm front continued to accelerate north. One of the cells even spawned an EF-1 Tornado in York County. Many times this setup would have spared South Jersey, but in this case there was a trailing cold front and a seabreeze front to interact. During the day on Sunday temperatures quickly climbed to 70 here, but that was short-lived however as the cool marine layer (seabreeze) started to move westward. Temperatures fell into the 50s across New Jersey anywhere within 20 miles of the coast, while areas just a bit further inland (Buena, Hammonton, Tabernacle) managed to hold onto the warmth. This set the stage for the explosive development (the distant light flashes Boyd saw) as the cold front moving east, interacted with the seabreeze moving west. There was lift, and with no cap in place storms were able to fire right up as the marine layer was pushed violently back out to sea. With upper levels so cold, there was plenty of hail reported with the system too. I had been watching the setup most of the day, and was even going to go out chasing with a buddy of mine, but the intense development happened so fast there wasn't even time to chase from here. Especially since it happened nearly overhead! I had an incredible light show here, followed by very heavy rain and wind. My buddy, who did go out chasing said there was nickel size hail as nearby as Weymouth. Since there was hail the storms did meet severe criteria, which the National Weather Service did end up issuing warnings for. The storms that hit areas of western NJ and eastern PA were not the same as those that developed over the eastern portions.
I have some pictures I'll be uploading to the photo forum later.
There’s an in-depth analysis for anybody who may have wanted it... there was lots going on behind the scenes
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I was out for awhile and shortly after sunset I started seeing lightning flashes, very intense but so far away that there was no thunder. It became a really cool fireworks show as the storm approached and eventually cloaked over the crescent moon. Suddenly the wind picked up and a dark haze surrounded me when I realized I'd better high-tail it back to the house! Got there just in time, we had about a half hour of hard rain and high winds, then it was over.
