The National Weather Service tornado warning for Howard County, Md., has been extended to 8:30 p.m.
The warning now includes Baltimore County and city. The warning expired for Carroll and Montgomery counties at 7:45 p.m.
At 7:37 p.m., radar indicated strong rotation in a severe thunderstorm 11 miles northwest of Columbia and moving east at 25 mph.
The warning is in effect until 7:45 p.m. People in the area should take cover. If there is no underground shelter, find an interior room on the lowest floor. Mobile homes and vehicles should be abandoned and windows should be avoided.
A severe thunderstorm warning for the same areas is in effect until 8:30 p.m. At 7:46 p.m. radar indicated a severe thunderstorm eight miles west of Ellicott City and moving east at 25 mph. Penny-size hail and wind gust up to 60 mph can be expected.
People should stay indoors and away from windows until the storm passes.