[Pyro7480]

Philly's part of a mini-tornado alley that stretches from York eastward.

I've heard of at least another south of there in the DC area (particularly since you had two tornadoes go through or near La Plata, MD). Do you have a source for that?

[dirtboy]

I saw a national tornado frequency map a few years back and you could see that there were was an uptick east of the Appalacians in the mid-Atlantic. I'll see if I can find it again.