Severe storms with a history of damaging winds and a confirmed tornado sighting moved through Maryland on Thursday afternoon, potentially the second outbreak of tornadoes in four days for the state.
The Storm Prediction Center meanwhile confirmed that morning storms that blew through the region could be classified as a "low-end derecho".
Local emergency officials confirmed a tornado on the ground near Olney in Montgomery County about 4 p.m., and minutes later near Columbia, according to the weather service. The sighting prompted tornado warnings eastward toward southern Howard County, northern Anne Arundel County and eastern Baltimore County.
The storms brought down trees and may have included at least one tornado, causing thousands of power outages. More than 12,000 Baltimore Gas and Electric Co. customers were without power as of about 5:15 p.m., mostly in Anne Arundel and Prince George's counties, with 15,000 outages restored throughout the day.
They also caused widespread flooding. A flash flood warning was in effect for Baltimore and southern Baltimore and Anne Arundel counties until 7:15 p.m.
The Bay Bridge closed in both directions as the storm passed.
Storms earlier Thursday downed trees and dropped up to ping-pong-ball-sized hail in northern counties earlier Thursday morning. The National Weather Service received report of a waterspout on the Chesapeake Bay, near Annapolis and the Bay Bridge, about 9:43 a.m. Trees were reported downed across Frederick, Carroll, Baltimore and Harford counties.
Baltimore-Washington International Thurgood Marshall Airport held inbound flights for a period Thursday morning due to thunderstorms. About 50 flights were affected as of about 10 a.m. More than 60 arriving flights have been delayed and a handful have been canceled. About 57 departing flights had been delayed by the weather here and at destinations.
Maryland Transit Authority officials said they called in extra personnel and supervisors to ensure the continuity of our service and emergency equipment and back-up generators have been tested.
Baltimore City and the Maryland Emergency Management Agency activated emergency command centers. MEMA was coordinating with emergency responders around the state to prepare.
Behind the storms, heat and humidity are expected to clear out. Skies are forecast to gradually clear Friday, with clear skies Saturday and partly cloudy skies Sunday.
High temperatures are forecast around 80 degrees Friday and Saturday and the mid-80s Sunday. Lows could fall to the lower to mid-60s.
Baltimore Sun reporters Kevin Rector and Candy Thomson contributed to this report.