(CNN) A flash flood warning has been issued for the Washington, D.C., metro area until 1:45 p.m. Monday by the National Weather Service.

In one hour, some spots just west of the nation's capital saw over 3 inches of rain, especially along the Potomac River.

Areas of concern include the Great Falls, Virginia, area and southeastern Montgomery County, Maryland.

Extremely heavy rain continues to fall over much of the area, including the District of Columbia.

Storms are also affecting airports, with traffic heading to Reagan National stopped on the ground. Departure delays by more than one hour have been reported.

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