Monday, September 03, 2012

Flash Flood Watch Through Tuesday Night


The region is under a flash flood watch through tomorrow night as we're stuck in a tropical overrunning setup locally. A stalled front is to our south and tropical air over the Southeast is trying to push back northeast into the region. The combination of that, an east wind off of the Atlantic, and the front are making for a soggy go of it in places today. Rainfall has exceeded three inches in parts of Chester County and has pushed over four in some parts of Delaware.  With more heavy rain across the region late this afternoon and evening the potential for localized flooding is legit and we could see a few inches of rain just from tonight's thunderstorm activity alone as it lifts northeast.

Computer guidance continues to suggest the potential for two inches of rain in the next 36-48 hours but these totals are likely underdone given the tropical fetch that's overriding the stable air that's in place at the surface. With tropical-like rains being an occasional part of the picture over the next two days, I could see some spots getting upwards of five additional inches to what has already fallen through 4 PM today.


Tomorrow's rainfall will be more widespread than today's across the region -- and likely just as slow moving.  Areas that dodged a bullet today probably will not be as lucky tomorrow to do so.  In tomorrow's case, the rainfall axis may shift somewhat to the north as the stalled front slips slowly northward.  Isaac's remnant moisture pushes in tomorrow and agitates the front further, which allots for the more widespread thunderstorm (or shower) development.

More:  Current Weather Page