...SEVERE THUNDERSTORMS POSSIBLE THIS AFTERNOON AND EVENING... A cold front approaching the region will interact with an unstable airmass to result in showers and thunderstorms. Some of these thunderstorms may become severe, especially between 2 PM this afternoon and 9 PM this evening. The main threats with these storms will be: * Damaging wind gusts * Heavy rainfall and flash flooding * Frequent lightning Take time today to review your severe weather action plan. Have a way to receive alerts from the National Weather Service, and be ready to seek safe shelter should storms approach your neighborhood or a warning is issued. By the National Weather Service, Sterling, Va.