Ground stops have been issued at Reagan National, Dulles, and Baltimore/Washington International airports as a fast-moving storm complex generated by an extreme heat wave is expected to race southeastward from eastern Ohio toward the Washington, DC metro area today, placing the entire region under a severe thunderstorm watch through 9 PM ET. The watch, issued by the National Weather Service at 1:15 PM ET, extends from Fredericksburg, Virginia, in the south to Frederick County, Maryland, in the north — covering more than 6 million people across the Beltway and its surrounding communities.
The primary hazards today are not flooding. They are 60 mph damaging wind gusts and large hail — a threat profile that is categorically different from last week’s storm pattern, which centered on a stalling low-pressure system and drought-saturated ground. The storm system heading toward DC today is a mesoscale convective system — a self-organized cluster of thunderstorms that can grow to hundreds of miles across — formed in the corridor between the summer’s heat dome over the south-central United States and cooler air across the northern tier of states.
What the Watch Covers and When Storms Are Expected
The National Weather Service severe thunderstorm watch covers the District of Columbia, Arlington County, Fairfax County, the City of Fairfax, the City of Alexandria, Anne Arundel County, Montgomery County, Charles County, Prince George’s County, Carroll County, and Frederick County in Maryland, plus the City of Fredericksburg, Fauquier County, the City of Manassas, Prince William County, and Stafford County in Virginia.
The Beltway area faces the greatest exposure, with the primary severe-weather window running from approximately 4 PM through 8 PM ET. Isolated storms could develop as early as 2 PM; the watch remains in effect until 9 PM ET. Severe thunderstorm warnings had already been issued for individual counties in Maryland and Virginia even as the broader watch remained active as of early afternoon…