Heat Ridge About To Pump Temps Up

We're starting the core and prime heat days of our heat wave today, with three days of nastiness ahead where temperatures and dew points combine to make it feel like it's over 100 each afternoon...perhaps even as high as 110 in the prime heat of the day tomorrow afternoon.   Some low clouds, haze, and light fog graze the region this morning as residual less hot air from yesterday lingers while the heat ridge bubbles in from the southwest.   Temperatures are starting out on the toasty side regardless -- generally in the 70's and on the way to topping out well into the 90's by day's end.

Nationally, the main focus of the heat is shifting a bit to the east and southeast from its position of the past few days.   Minnesota and most of the Upper Midwest have seen the passage of a cool front and the introduction of some relief in the temperatures and humidity, with the heat dome shifting to the Ohio Valley and Appalachians for the next few days.  You can see the vast swath of real estate that are under some form of heat advisory, warning, or watch over the next couple of days (inland areas in a red shading) -- effectively close to 2000 miles from Massachusetts to Oklahoma.   Locally, we're under an excessive heat warning through Saturday.

Today's peak heat features heat index values between 102 and 107.   Based on an assumption that we reach high temperatures from 94-97 locally, with dew point values in the low or middle 70's, the heat index below is calculated for a number of different locations based on different combinations.   Even with a lower high temperature, a higher dew point can offset the "cooling" benefit of three degrees and give you an apparent temperature as high, if not higher, than the heat index of a locale with a higher temperature and lower dew point.   That's why it's more critical to know what the heat index is as opposed to simply knowing how high the air temperature is.    All of the air temperatures over the next three days will be hot -- perhaps record breaking in spots -- but the bigger story will be the combination of this heat with dew points that are borderline tropical.   That combination compounds air temperatures in the upper 90's or 100ish and makes it feel like it's a good 5-12 degrees warmer.

Most of us would probably feel better if we were talking about subzero wind chills this morning and not heat index values in the 100's or low 110's!   Regardless, stay cool (or as cool as possible) and drink lots of water.

More:  Current Weather Page

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.

Industrial Sized Blowtorch

No puns needed with this upcoming heat event.   Whether or not we make it through Friday to get the "official" heat wave designation it doesn't matter.   Wednesday and Thursday's heat will be nasty and malicious.    While dew points will not be as bad as last week's heat event, we are looking at dew points that will get into the 60's and temperatures that will be a few degrees higher than the last heat event.   As a result, the heat index values (what it really feels like) will still approach if not exceed 100.   The National Weather Service has heat advisories and heat warnings out for Wednesday and Thursday for much of the region, with Philadelphia potentially seeing a run at 100 on Thursday if everything comes together perfectly.

The next two days also feature potential record highs for the region, with tomorrow's record the 'easier' of the two to hit.   Philadelphia's record of 95 was set back in 2008 and outside of Atlantic City and Trenton, most of the records are relatively reachable....and even in those two places the record high might get knocked out if everything comes together right.    On the chance we hit 100 on either day of the next two, it would be the third earliest 100 on record.   June 5th and 6th, 1925 featured 100 degree heat and are the earliest standards for triple digit heat in the Philly region.

Relief comes in the way of a frontal boundary that approaches the region Thursday night, crosses slowly on Friday before stalling just to our south.   This could mean a less-than-stellar weekend as thunderstorm chances increase.   At least the heat will end...