Update at 6:30 p.m. — The ground stop at Reagan National has been lifted, but major delays are being reported. From the FAA:
Due to WEATHER / THUNDERSTORMS, there is a Traffic Management Program in effect for traffic arriving Ronald Reagan Washington National Airport, Washington, DC (DCA). This is causing some arriving flights to be delayed an average of 3 hours and 27 minutes. To see if you may be affected, select your departure airport and check “Delays by Destination”.