The National Weather Service in San Diego has issued a flash flood warning for east central San Diego County until 6:30 p.m.At 3:35 p.m. NWS doppler radar indicated persistent thunderstorms and heavy showers over Shelter Valley, Agua Caliente Springs, and Canebrake which will likely produce flash flooding.Locations in the warning include but are not limited to Ocotillo Wells, San Felipe Creek, Vallecito Wash, Fish Creek, Harper Canyon Wash, and Highway 78.Earlier, a thunderstorm northeast of Borrego Springs prompted the National Weather Service to issue a flash flood warning for the area Wednesday, as a flash flood watch remained in effect for other mountain and desert areas.The flash flood warning for northeastern San Diego County including Borrego Springs was set to remain in effect until 4 p.m., according to the NWS.Doppler radar indicated the storm about five miles northeast of Borrego Springs was capable of producing considerable runoff in nearby rural areas in northeastern San Diego County, such as Coyote Creek the warning stated. Flowing waters could run over state Routes 78 and 22 and heavy rains could impact the San Felipe Creek as the storm moves east, the NWS stated.Between 12:45 and 1:45 p.m., rainfall gauges in Borrego Springs recorded 0.42 inches of precipitation.Other mountain and desert areas were under a flash flood watch until 6 p.m., according to the NWS.A flash flood watch means conditions are favorable for thunderstorms that could produce enough runoff to cause flash flooding, according to NWS forecaster Mike Watkins.The unstable weather should move easterly Wednesday afternoon, according to the NWS. Runoff from downpours may turn dry washes, creeks, small streams into raging torrents, especially along desert slopes and valley floors, forecasters said.Rock and mud slides are possible near steep terrain and in recently burned areas, according to the NWS.Rainfall gauges recorded about a quarter-inch of precipitation near Ramona an in Oak Grove between 8 a.m. and 2 p.m., and 0.18 inches fell in Anza.Watkins said mountain and desert residents should keep abreast of conditions and stay away from fast-running water."There's a saying we have, 'turn around, don't drown,'" Watkins said. "In other words, if you see a lot of water across the road, turn around. Don't drive through fast-flowing water."Rainfall gauges recorded about a quarter-inch of precipitation in Oak Grove and near Ramona between 6 a.m. and noon, and 0.09 inches fell in Palomar.