Update, 4:30 PM: We're seeing a bit of a regenesis in the storm activity, especially in Bucks into Mercer Counties where a severe warning is now out. Scattered activity is continued on back to the west into Chester County but the storms farther west, at this point, aren't as strong.
Update, 3:30 PM: The "line" I talked about earlier has fallen apart a good bit -- looking at some of the atmospheric data one would think the potential would really exist -- there is a lot of atmospheric juice and instability. Dynamics aloft, however, aren't as favorable. The upper level jet that was modeled to be overhead today is instead a bit farther north, with lighter winds aloft at the surface and a less optimal setup for severe around here.
Radar is showing a bit of a weak trough/boundary line across the northern/western suburbs. Nothing has popped from it yet but if anything does fire development could be quick as it may be a focal point for localized thunderstorm development later on. Unfortunately, things are "stuck" because of a less than favorable upper level of the atmosphere as winds aloft may not be strong enough to help aid in storm development.
Update, 2:45 PM: A couple of smaller storms have started to pop around the city and suburbs. Nothing severe at this point in the city or suburban counties (not including Berks/Lehigh, which are both under warnings until 3:45 PM) but the earlier mentioned line of storms that developed along the lee trough have gotten a bit better organized and now generally extend from Stroudsburg to Allentown to Reading and farther south and then west. We'll probably see that line continue to fill in as it moves east and more storms continue to pop ahead of the line in the next hour.
Lots of stuff to talk about this afternoon! Not only do we have the heat warning but we have two severe weather watches out there. First, a Severe Thunderstorm Watch until 5 PM for Central into Northeast Pennsylvania, with a Tornado Watch out until 8 PM for the Philadelphia area on north.
A supercell thunderstorm fired up across Central Pennsylvania and zipped east into Northeast PA early this afternoon. That cell will pass through North Jersey and towards the northern NYC suburbs over the next couple of hours. Our development is setting up out near Harrisburg, along the "lee" trough that develops along and just east of the Appalachian Mountains, where you get a bit of a dry line between slightly cooler/less humid mountain air and the moist, humid air that can pool across Central and Southeastern Pennsylvania. Thunderstorms are starting to fire up and will gravitate east over the next few hours, with the Philadelphia region's best chance for thunder generally between 3 and 6 PM, possibly a bit later than that to our east.
Damaging winds are more likely than tornadoes but a tornado can't be ruled out -- the Storm Prediction Center has Philly and points north in a 5% chance area whereas damaging wind has a 30% chance of verifying within 25 miles of one's spot. Regardless, expect storms to continue to pop over the coming hours and work towards the region, with our best chances of getting hit after 3 PM.
It also would not surprise me if some sort of watch gets issued for Delaware, Maryland, and the rest of South Jersey within the next hour or two.
Update, 2:30 PM: Severe Thunderstorm Watch now out for South Jersey and Delaware (basically the rest of the region not under the Tornado Watch) until 10 PM.
We'll have updates within this post as the afternoon progresses.
More: Current Weather Page
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