Wednesday, July 18, 2012

Hot To Start, Stormy To Finish

It's in the upper half of the 70's to the lower 80's early this morning around the region...a pretty nasty start to what is shaping up as a pretty nasty temperature day around the region.  Temperatures have been kept up a bit overnight by the presence of some high clouds overhead plus increasing moisture out in advance of a cool front that's slowly slipping south.  This front will begin to cross the state today but it will take the better part of three days to finish the journey through the region.  That could result in a rather thundery stretch of weather starting later this afternoon.

It's quiet now and should remain that way through the morning hours, with sunshine filtered through a few patches of high clouds.  This will get temperatures to take off, pushing us to the upper half of the 90's this afternoon around the region.  Adding dew point values in the lower 70's in the region and the resulting heat index will range between 100 and 107 at peak heat throughout the region.  Heat advisories (orange shading on the graphic above) and warnings (magenta) remain in place today on what may end up being the most oppressive day of the year from a heat index standpoint.  We were hotter back on the 7th (101 in Philly) but heat index values were not much higher than the temperature.  Today will feature higher humidity and temperatures just a couple of notches cooler -- it *could* end up a bit more oppressive.

Regarding the stormy part of the forecast, computer modeling continues to suggest that thunderstorms are likely this afternoon and evening across the region.  Some of those storms will be severe with gusty winds, perhaps hail, as well as heavy rainfall as moisture content in the atmosphere is high.  Timing suggests thunderstorms are possible after 3 PM, pushing south and southeast through the region....with the earlier timing focused on the Lehigh Valley.