By Michael E. Ruane
Washington Post Staff Writer
Friday, August 13, 2010; B01
A second wave of violent weather roared across the Washington region late Thursday, dumping rain and hail and whipping up dangerous winds only 12 hours after a similar line of storms brought havoc to the area in the morning.
Violent downpours from gusty thunderstorms drenched areas already soaked from the morning's deluge, and the National Weather Service issued a series of tornado and flash-flood warnings from northern Maryland to as far south as Richmond.
But after leaving inundated streets, downed trees and tens of thousands of power outages over a huge swath of the region, the severe weather weakened and the threat of tornadoes dissipated, though waterspouts were reported on the Honga River on Maryland's Eastern Shore.
The region might see more showers Friday, but forecasters said that any precipitation would fall far short of Thursday's levels, when a minivan was swept into Rock Creek in the District and carried a quarter-mile downstream. The driver escaped unhurt.
It was the third day of violent, destructive weather locally in three weeks. And it came on top of a July earthquake and a summer of excruciating heat.
Repent, someone tweeted, partly in jest.
Thursday's storms struck a week after a similar system smashed across Alexandria and Prince George's County on Aug. 5. Another, even stronger, system pounded Montgomery County and the District on July 25.
The damage and power outages from this summer's storms seem unprecedented, and forecasters have noted that it has been a particularly hot summer. There have been 51 days of 90-degree or higher temperatures, according to the Capital Weather Gang, and 20 days of 95-degree readings or higher.
There have also been four 100-degree days.
"This has been a very extreme summer," said Dan Stillman of the Capital Weather Gang, noting that there were no 100-degree days last summer and only 21 days when the temperature reached 90.
But Stillman said the heat extremes might not be entirely to blame for the severe weather.
"You could easily get the kind of storms we've gotten when you have summer temperatures that are pretty warm and not quite as hot," he said.
The day began ominously. At Reagan National Airport, the temperature was reported as 82 degrees shortly after dawn. The air was steamy, with humidity over 70 percent. And the morning sky over much of the Washington area was dark and still, as if with the pent-up gloom of weeks of heat and irritation.
About 7:15 am, the sky erupted in torrential thunderstorms that deluged parts of the area in the midst of the morning rush.
Streets flooded. Trees came crashing down. Power went out. Parts of the Metro system were hobbled, and traffic in some places crawled to a halt amid rivers of muddy water.
Rain -- an inch and a half in an hour -- was the main culprit. It was dumped by a 60-mile-long squall line that reached from just outside Baltimore to the District.
Flash floods across the area stranded motorists atop their cars. More than 100,000 people lost power, local utilities said, and Pepco said repairs could again take days.
At 9 p.m., about 63,000 people were without power. The vast majority were Pepco customers, about 49,300 of them in Montgomery, 6,800 in the District and 3,800 in Prince George's. Dominion Virginia Power reported about 2,600 customers without power in Northern Virginia, and BG&E had about 225 outages in Maryland's D.C. suburbs.
Among other things, the morning's hour-long deluge brought a tree down on a house in Chevy Chase, showering an infant in a crib with debris.
Robert Anderson and his wife, Betsy, ran upstairs to find Jaymes, their two 2-month-old son, in his crib covered with parts of the tree, the ceiling, and hunks of slate roofing, brick and insulation. "I just ran over and started throwing stuff off of him," Anderson said.
He rinsed Jaymes off in a sink, and the boy began to cry. "Okay," Anderson thought, "crying is probably a good sign." The baby suffered only minor scrapes.
The storm tore a 50-foot hole in the roof of large church in Camp Springs. And it blew down tents at the Montgomery County Fairgrounds, where a camel named Matt suffered a head injury when struck by downed tree limb.
Traffic lights were out across the region. And trees and limbs littered roadways, lawns and houses.
There were delays on Metro, as the Cleveland Park and Forest Glen stations were temporarily closed.
There were also delays at local airports, as aircraft had to wait out the passing squall lines. And roads were closed by high water and fallen debris across the area.
In Montgomery County, stranded motorists were described as taking to the roofs of their vehicles as muddy water inundated an area around Veirs Mill Road and Connecticut Avenue. Canal Road NW became a lake, witnesses said, as did Rhode Island Avenue in the District and Route 1 in Beltsville.
Shady Grove Adventist Hospital in Rockville had to reschedule surgeries after flooding in its waiting rooms and surgical services area, and United Medical Center in Southeast Washington had to rely on generators for most of the morning when the hospital lost power for several hours.
In Gaithersburg, rescue workers responded to a report of a tree that had fallen through the roof of an apartment building in the 500 block of Frederick Avenue.
Workers found that the tree had damaged a common stairway, so they used 24-foot ladders to rescue residents. No life-threatening injuries were reported, but two people were taken to a hospital. As the day went on, amid mounting heat and humidity and the still unstable atmosphere, the second wave of weather cooked up and spawned fast-moving storms that galloped across the area from north to south.
Forecasters said the "backdoor" cold front that slipped into the area from the northeast and stalled here was partly to blame for Thursday's unsettled atmosphere.
Friday was expected to be cloudy, with a chance of showers, but not so stormy, and Saturday, partly sunny and cooler.
Staff writers Lori Aratani, Mary Pat Flaherty, Hamil R. Harris, Dan Morse, Rick Rojas, Michael Rosenwald, Kevin Sieff and Ann Scott Tyson contributed to this report.