Tuesday, January 29, 2013

Winter Squall Sets Up Flood & Wind Watches

Flash Flood Watches are out for many of us for tomorrow afternoon and evening thanks to the approaching storm system that's dropping heavy rain, thunderstorms, and severe weather across the Midwest this evening.  That system is our business for tomorrow evening and will push in during the evening commute with a round of rain, wind, and possibly some thunder.

While the best chances of thunder are to our south and we're not under any severe criteria risk for tomorrow yet in Philadelphia (south of the city is), there's the potential for gusty winds along and ahead of the squall line that will push through tomorrow evening.    Winds in the high wind watch area could exceed 60 mph as a low level jet of over 80 mph will likely zip on through tomorrow evening.  These type of winds can transport down to the surface in the form of strong gusts...but the highest likelihood for those gusts will be along the Shore.  Along and west of I-95, wind advisories are possible tomorrow evening as winds could reach 40 mph in gusts, perhaps a notch higher.

Rainfall varies on modeling -- the NAM is the lower end of guidance, the GFS the higher end, and the Euro is the middle ground.  The Euro averages around an inch of rain for I-95, a bit less east and south, a bit more north and west.  That said, the ground is frozen in many spots so an inch of rain is going to cause runoff and flooding problems for the usual suspect streams and if the GFS' higher rainfall totals verify, stream flooding in places that don't always flood can't be ruled out.

We will update timing on all of this tomorrow morning.