Sunday, August 05, 2012

Soaking On Tap For Some Later Today

Warmth, tropical humidity, and a frontal boundary to the west are coming together to produce an "ugh" day across the region on a number of levels. First, temperatures starting off around 80 at 8 AM in the city with a decent southwest breeze. Dew point values in the 70's are yielding heat index values in the lower and middle 80's at 8 AM across the region.  As temperatures climb to around or just above 90 this afternoon, heat index values may flirt with or just pass 100 degrees at peak heat.

Second, that warmth and moisture will yield thunderstorms later on today as a front works in from the west.  Storms are already firing up across Central PA along an old boundary from a squall line that zipped across the Midwest and Great Lakes last night.  Those storms are moving northeast out ahead of the main front, which is back in Ohio.  As the front moves into our tropical airmass, more thunderstorm development will be likely later on today.  The best chances will be west of the city this afternoon (Central Pennsylvania), shifting into Northeast Pennsylvania this evening, and into Philadelphia late this evening.   However, storm chances are possible this afternoon out in front of the main mess...mostly scattered, less widespread.  Tonight appears to be the more "widespread" thunder threat.

Severe thunderstorms can't be ruled out but the bigger threat will be heavy rainfall.

Flash flood watches are out in the Poconos and in North Jersey this afternoon and evening for the prospect of localized flooding.  Even locally, some areas have picked up quite a bit of rain in the past week and thunderstorms could yield some localized ponding of water on roads and in low lying areas.

We'll update the thunder threat later on as storms fire up...until then, "enjoy" the Miami-like day that's in place over us.