That means weather conditions are are favorable for the spread of fires.
...RED FLAG WARNING IN EFFECT FROM NOON TO 6 PM EST FRIDAY FOR GUSTY WINDS AND LOW HUMIDITIES FOR NORTHERN MARYLAND...NORTHERN VIRGINIA AND EASTERN WEST VIRGINIA... The National Weather Service in Baltimore MD/Washington has issued a Red Flag Warning for gusty winds and low humidities, which is in effect from noon to 6 PM EST Friday. * TIMING...From noon to 6 PM EST Friday. * WINDS...West 10 to 15 mph with gusts up to 30 mph. * RELATIVE HUMIDITY...As low as 24 percent. * IMPACTS...The combination of dry conditions, low humidity, and strong gusty winds may result in favorable conditions for the rapid spread of fires. * FUEL MOISTURE...Less than 10 percent. PRECAUTIONARY/PREPAREDNESS ACTIONS... A Red Flag Warning means that critical fire weather conditions are either occurring now, or will shortly. A combination of strong winds, low relative humidity, and warm temperatures can contribute to extreme fire behavior. The Red Flag warning covers Frederick, Carroll and Washington Counties; parts of Montgomery and Howard Counties; Loudon County, Virginia; and Jefferson and Berkely Counties in West Virginia.
By The National Weather Service, Sterling, Va.