The National Weather Service in Sterling Virginia has issued a * Severe Thunderstorm Warning for... Northeastern Washington County in north central Maryland... Northwestern Frederick County in north central Maryland... * Until 415 PM EDT. * At 331 PM EDT, a severe thunderstorm was located near Boonsboro, or 7 miles south of Municipal Stadium, moving east at 20 mph. HAZARD...60 mph wind gusts. SOURCE...Radar indicated. IMPACT...Damaging winds will cause some trees and large branches to fall. This could injure those outdoors, as well as damage homes and vehicles. Roadways may become blocked by downed trees. Localized power outages are possible. Unsecured light objects may become projectiles. * Locations impacted include... Frederick, Hagerstown, Thurmont, Ballenger Creek, Robinwood, Walkersville, Boonsboro, Smithsburg, Mount Aetna, Mount Lena, San Mar, Clover Hill, Discovery-Spring Garden, Wolfsville, Saint James, Linganore-Bartonsville, Myersville, Cavetown, Keedysville and Woodsboro. PRECAUTIONARY/PREPAREDNESS ACTIONS... Large hail and damaging winds and continuous cloud to ground lightning is occurring with this storm. Move indoors immediately. Lightning is one of nature`s leading killers. Remember, if you can hear thunder, you are close enough to be struck by lightning. By The National Weather Service, Sterling, Va.