A brief but violent thunderstorm crossed the Washington area with winds up to 50 miles an hour yesterday, causing power interruptions, halting flight operations at Andrews Air Force Base and forcing President Reagan to travel by motorcade instead of helicopter from Andrews to the White House.

The storm, bearing heavy rain and hail, struck about 2 p.m. and hit hardest in Prince George's and Fairfax counties, authorities said.

Andrews was forced to close because of debris blown onto its runways. The wind ripped apart the roofs of the arts and crafts center and a furnishings warehouse on the base, a spokesman at Andrews said.

No injuries were reported.

President Reagan's plane, Air Force One, arriving from Atlanta where the president had addressed the American Bar Association, was able to land at the base. But the storm prevented the president from taking the usual helicopter ride from Andrews to the White House lawn. He made the trip by motorcade instead.

The press plane accompanying the president was diverted to National Airport.

Brig. Gen. Leslie Kampschror, deputy commanding general of the D. C. National Guard, said three Air National Guard jets at Andrews--an F-4 fighter, a trainer and a transport--apparently were damaged. He said the full extent of the damage should be known today.

Andrews was closed for about an hour and a half.

Virginia Electric & Power Co. reported that about 7,300 of its customers--most of them in Springfield, Woodbridge and Alexandria--were without power for about a half-hour.

Some 3,000 customers of the Potomac Electric Power Co.--most of them in Southern Prince George's county--were without power throughout the afternoon.

Prince George's County Executive Parris Glendening sent home county workers stationed in Upper Marlboro at 2:30 p.m. after power went out in the county's administration building.

Glendening said the administration building was without lights and office workers were unable to tell whether phones were ringing. He said one elevator remained running on an emergency generator.

Prince George's fire officials reported 14 incidents of power lines downed and 10 of brush fires caused by lightning.