A local weather photog here in DC (Kevin Ambrose) has taken some fantastic weather shots in and around DC. Chasing in the DC is impossible, but if you set-up right, and with plenty of time, you can grab some of the best (and really make good bank!!) on the shots here. I going to try and get Bill Hark and William Coyle up here for some of those shots if I can. I know they've seen some good stuff down near the Richmond area, with the city backdrop. Maybe they'll chime in on the thread.
Best I've done is from the northern suburbs in Monkey...ahhhh....Montgomery County, MD. I have a number of 'high' spots that I'll head to in the area, some that are man made, some that are not. In many of those, you can see the 'edge city' kind of city backdrop, but nothing like the urban core.