Five minutes after a storm swept through Loudoun County last Wednesday, more than 4,000 residents lost electrical power.
At 3 p.m., two small tornadoes moved across the north side of Leesburg, their paths a quarter mile apart and with wind estimates of 70 miles per hour, rated as F-0 storms. Within 10 minutes, the tornadoes blew out of the county and across the Potomac River into Montgomery County and to the west side of Germantown, fading out by 3:25 p.m.
The tornadoes and associated rain showers moving across the Washington, D.C. area that afternoon resulted from a cool air system clashing with warm humid air. The unseasonably high temperatures during the weekend and on Monday and Tuesday averaged in the 80s, 20 degrees higher than the average for the time of the year.
"Whenever you have two air masses that strongly different, you’re always likely to have turbulent weather," said Howard Silverman, meteorologist for the National Weather Service.
The storm, which continued into Thursday, damaged power lines and equipment operated by Dominion Virginia Power, leaving 4,200 customers without power by 3:15 p.m. in Sterling, Leesburg, Aldie, Middleburg, Upperville and Paris. Dominion returned power to most of the customers by 11 p.m. that day and to another 100 customers on Thursday afternoon. The storm hit the Dry Mill Road area in Leesburg the heaviest, breaking a 50-foot utility pole and 18 cross arms and mangling some of the wiring.
"We generally will have outages when there is inclement weather that involves high winds or lightning," said Le-ha Anderson, manager for media and community relations for Dominion.
In addition, the tornadoes damaged trees, peeled off home siding and tore off shingles from homes, Silverman said. "By in large, the damage caused by an F-O storm is on the minor side," he said.