Thursday, July 18, 2013

Continued Heat, Now With Extra Humidity

We continue the heat parade today with an added nudge of humidity to kick the nasty factor up a notch or two.  Southwesterly winds at the surface will help pull higher dew points northeast into the region today, with dew points running close to or above 70.  Factoring in temperatures that will rival yesterday's mid 90 degree highs, and the stage is set for heat index values that nudge over 100 at peak heat this afternoon.  Excessive heat warnings are out for the immediate Philly metro, with heat advisories issued for the outlying suburbs northwest, plus the Lehigh Valley, the southern two-thirds of Delaware, and the northern two-thirds of New Jersey (basically everything in orange).

The ridge of high pressure that's responsible for the heat the last few days has started to wane somewhat. While it's still pretty strong, it isn't as in control of the weather over us as it was on Tuesday and Wednesday.  The result will the possibility of a few pop up thunderstorms this afternoon to our west and northwest, along or just northwest of Blue Mountain (Poconos or Central PA hills).  These storms could drift down towards the Lehigh Valley or Reading by evening but odds favor the vast, vast majority of the day being dry, hot, and humid.  The vast majority of us will also be dry, hot, and humid as well.

Expect highs in the afternoon in the mid 90's, with heat index values around or above 100 at peak heat.