Thunderstorms that roared to the edge of Baltimore dropped more than 5 inches of rain in some areas yesterday, and evening lightning strikes knocked out radar and blasted holes in a runway at the Baltimore-Washington International Airport.
Flights were held up for hours and additional delays are expected this morning.
Howard County took a major hit and Anne Arundel County was belted even harder, with storms snarling traffic and knocking out power to more than 12,000 homes there.
Across Baltimore Gas and Electric Co.'s Central Maryland system, more than 20,000 customers were blacked out for varying lengths of time - and repair work was expected to continue into this morning, a spokesman said.
The on-again, off-again downpours were localized for much of the day in areas east and southeast of BWI. By late afternoon, Riviera Beach had recorded more than 5 inches of rain.
Storms also delayed the start of last night's Orioles game.
Planes at the airport were grounded and arriving flights were diverted elsewhere at 6:24 p.m., said BWI spokeswoman Harriett Sagel.
A lightning strike left two holes in Runway 1028, she said, and crews worked more than 30 minutes to patch them.
Ten minutes after that strike, lightning knocked out radar.
"It was a direct hit to the radar system," Sagel said.
Departures were delayed for nearly two hours, and arrivals slightly longer, she said, but thousands of passengers had to add hours - and perhaps an overnight stay - to their trips.
More delays were expected this morning, she said.
In a portion of Howard County, as much as 3 inches of rain fell in little more than an hour, the National Weather Service said - a deluge that caused the Patapsco River to overflow its banks, temporarily closing a stretch of U.S. 1 just south of the Baltimore County border.
Anne Arundel had episodes of flooding as well.
A storm-water management pond at Fort Smallwood Road and Edwin Raynor Boulevard in Riviera Beach overflowed at 3:45 p.m., the same time the National Weather Service's first flash-flood warning for the area expired.
A storm drain connected to the pond dumped seed, straw and sediment into the yards of three residences along Fort Smallwood and Rock Hill roads.
Forecasters tracking the storm agreed that the weather patterns were unusual.
Weather service forecaster Jim DeCarufel said the clouds hovered over the Riviera Beach area while little or no rain fell on much of Baltimore.
"The fact that it's just sitting there, and there's copious rainfall in a particular area, is a little bit strange," he said.