Excessive Heat Watches & Warnings Up

The prospect of the worst of the season's longest heat wave is coming upon us for late this week, with Excessive Heat Watches and Warnings out for much of the region due to the nasty combination of heat and humidity that is poised to worsen over the latter half of the week.   Excessive Heat Warnings are out for the Delaware Valley for now through at least Thursday, likely extending to Saturday given current trends, with watches out in Central Pennsylvania and in the New York Metro area for later this week.

We all know it's going to be hot, with computer guidance suggesting 100 is certainly within possibility for Friday and upper 90's sandwiching around that for both Thursday and Saturday.   The heat itself is bad enough and on Friday and Saturday, potentially record breaking.  However, the humidity will be the worse impact as dew point values in the lower 70's could yield heat index values upwards of 110 in some parts of town.   The heat/humidity combination is arguably much, much more potent and to be frank, it doesn't matter if anyone is forecasting 100 or not...the heat index will be higher and frankly makes the weather that much worse.

Thursday's records are rather tough to hit but Friday could pose a potential record breaking day, especially in Atlantic City and perhaps Philadelphia.  Saturday's record could be tied in many locations.   Even if we don't break a record, Friday will likely be the season's hottest day in terms of both temperatures and heat index.

One More Record Run

Another day of near or breaking record heat is soon upon us.   Temperatures today will be a couple of degrees higher than yesterday when the thermometer topped out at 97 in Philadelphia.   Could we see 100 in Philadelphia?   It's going to be a close call but we're predicting 99 in the city, which would squeak past the record high of 98 set back in 1933.   '33 is a common theme as many of today's records are from that year.   The easiest of the records today is in Wilmington at 96.

Relief is on the way, however, with a cold front about to slide east.  Temperatures yesterday afternoon were 30-40 degrees cooler in Minnesota than they were on Tuesday, when many places were over 100 degrees.   The Minnesota level of relief will not get here, however, as the front stalls out nearby.   However, temperatures by Saturday will be some 15-20 degrees cooler than they will be later on today and those morning temperatures we experience heading out the door to work will probably turn out close to the high for Saturday.    With the front stalling nearby we'll have thunderstorms to deal with...but I think for many of us having thunderstorms is a better thing to deal with than having temperatures near 100?

All About The Sun

How much sun we get on Monday will determine how warm we get...with a really warm airmass aloft ahead of a cold front that will march east towards us for Monday night, the potential for record temperatures is still definitely on the map...but we need the sun to break through the stable airmass at the surface that has allowed for clouds to develop over us.   Provided sunshine breaks out in time, temperatures in the lower and middle 80's can't be ruled out before day's end.

Record highs are most attainable at Allentown and Reading -- they are the farthest inland and most likely to get sunshine during the day.   Skies should brighten from west to east in the morning, meaning Trenton and Philadelphia could get in on the record fun if sunshine breaks through the clouds fast enough.   The Shore will be the last to brighten and the coolest, temperatures likely struggling to get above 65 and perhaps dealing with fog right along the coast as wind trajectory (south-southwest) isn't ideal for offshore conditions and significant warming.