A blinding scrim of thunderstorms that swept across the Washington area yesterday pelted National Airport with three-quarter-inch hail, marred the Anacostia Riverfest with a display of lightning that killed one man, and brought a premature conclusion to the final broadcast of "A Prairie Home Companion."

The National Weather Service said last night that a swift line of storms muscled east through the area last evening at about 30 miles an hour, with the heaviest deluge coming about 7.

At the storm's peak, about 1,500 Virginia Power customers -- most in northern Arlington -- were without power and dozens of minor accidents, felled tree limbs and flooded intersections were reported.

An unidentified man at the Potomac Riverfest celebration in Anacostia Park was struck by lightning about 7, D.C. fire officials said. He was pronounced dead at Greater Southeast Community Hospital, and officials were still trying to identify him late last night.

At least three other deaths, in two unrelated traffic accidents, were reported in the wake of the storms.

At about 7:20, Maryland state police said, an 8-year-old Springfield girl was thrown from a hatchback and killed when the car in which she was riding on southbound I-95 at Rte. 212 apparently went out of control and struck a guardrail.

Police said Jennifer Pauline Rogers, 7925 St. George's Ct., was killed when the car driven by her mother, Kimberly Jane Rogers, went out of control as a result of excessive speed and slick roads.

In the second, D.C. police said a passenger car that had apparently made an illegal U-turn was driving the wrong way on eastbound New York Avenue a half-mile west of the Baltimore-Washington Parkway when it struck a Greyhound bus head-on about 9:15.

Two of the victims were taken to Washington Hospital Center's MedStar unit, where one was pronounced dead and another was in stable condition last night, according to a hospital spokeswoman. A third victim was taken to Prince George's General Hospital, where he also died. No identifications were available last night.

All three were apparently riders in the car; witnesses said that several people in the bus, which was bound for Harrisburg, Pa., also appeared to have minor injuries, but those reports could not be confirmed last night.

Traffic from the Baltimore-Washington Parkway was diverted onto Blandensburg Avenue, and portions of northbound New York Avenue were closed off by police after the crash.

National Weather Service meteorologist Steve Hogan said last night that the storm front, which reached from western Virginia to the northern Chesapeake Bay, built up when an older cluster of storms in Pennsylvania collided with an unstable air mass that formed over the Blue Ridge mountains.

The cordon of storms formed in a line extending from Baltimore County just north of Frederick to Martinsburg, W.Va., and began moving into the Washington suburbs shortly after 6.

Gusts of up to 53 miles an hour were recorded at Dulles International Airport and 45 miles an hour at National Airport. Temperatures dropped 17 degrees, from 85 to 68, as the storms flashed through.

No tornado sightings were reported in the area. Although the six-hour severe-storm watch was canceled after 9 p.m., storms and showers were expected to continue overnight, and Hogan said that with temperatures back in the high 80s today, more storms were possible this afternoon.

"This is Washington . . . this is summer," Hogan said.

WETA-FM, which was scheduled to air the final live broadcast of Garrison Keillor's popular "A Prairie Home Companion," the send-up of old-timey fireside theater that features the town of Lake Wobegon, Minn., lost its power at 6:20 p.m., about 15 minutes into the two-hour show, when lightning struck a transmitter and "fried several wires" and pieces of relay equipment, according to broadcast engineer Mary Cliff.

Station officials said power was restored about 75 minutes later, and that the show was replayed at 9 and would be repeated again at 1 p.m. today.

Staff reporters Rowena Daly and Joe Mackall contributed to this report.