Wednesday, June 20, 2012

June 21st, 2012 Forecast

Today's been hot....tomorrow is going to be hotter as the core of the mid level heat ridge is overhead early in the day and gives us the boost needed in the atmosphere to make a record run tomorrow afternoon.  Philly's record high is 99 -- we're projecting 98.  It doesn't matter if we hit the record, reach 100, come up's going to be a nasty afternoon with plenty of heat and enough humidity around to make it feel a few degrees warmer than the actual air temperature.   A couple of rogue 100 degree readings are possible along I-95 or just east of it in New Jersey.  How hot we ultimately get is dependent on wind trajectory -- a more westerly breeze tomorrow will help us thanks to downslope conditions from hills in Pennsylvania and will help mix some less humid air down from aloft.

 It certainly doesn't help that we'll be starting off in the middle 70's along I-95 tonight, perhaps even near 80, as a warm night around the Delaware Valley takes hold.  A pretty good chance that your air conditioner...or your neighbor's AC unit...will be buzzing quite a lot overnight.

A cool front begins to approach the region tomorrow afternoon but it will take until Friday night to completely cross the region.  This front will trigger a few afternoon thunderstorms across Central Pennsylvania during the afternoon hours tomorrow, with a few of these storms slipping through Thursday evening around portions of our area.  Squall lines of storms aren't likely and most of the thunder that fires looks to be scattered or pop up in nature.   However, the heat ridge weakens as the front approaches and tomorrow's heat will be the last of the run towards 100 for quite a while as temperatures on Friday will be much closer to 90 for a high.