Update at 10:25- Bob Ryan - The storms to our north and west have diminished and the threat of severe weather is essentially gone. There will be cool showers coming through all the lightning has ended. Much cooler Wednesday
With a potent cold front approaching the region, southerly winds have helped usher in a warm and moist airmass out ahead of it. This has allowed for some instability across the region, but an 18Z weather balloon sounding shows a big capping inversion which has acted to inhibit development of thunderstorms ahead of the front. Because of this feature, we are not anticipating thunderstorms until the front moves through later on this evening.
The timing should be closer to 7pm to 11pm for the D.C. Metro and surrounding suburbs. The primary threat for severe weather will be in the form of damaging wind gusts. As far as rainfall potential is concerned, up to an inch may be possible in some locations, particularly where there are thunderstorms. Most of the area should receive around a half of an inch. Winds will continue to be breezy through the overnight hours, changing from southwest to northwest as the front moves through and gusting up to 30 m.p.h. Temperatures will remain in the 80s this afternoon, but will fall into the 50s tonight, and should only reach around the 60 degree mark tomorrow.