The National Weather Service in Phoenix has issued a * Flash Flood Warning for... Riverside County in southern California... San Bernardino County in southern California... * Until 730 PM PDT. * At 324 PM PDT, Doppler radar indicated thunderstorms producing heavy rain across the warned area. Flash flooding is ongoing or expected to begin shortly. HAZARD...Life threatening flash flooding. Thunderstorms producing flash flooding. SOURCE...Doppler radar. IMPACT...Life threatening flash flooding of creeks and streams, hiking trails, dirt roads, highways, streets and underpasses. * Primary locations that will experience flash flooding include... Joshua Tree National Park.