SAN DIEGO COUNTY MOUNTAINS-SAN BERNARDINO COUNTY MOUNTAINS-RIVERSIDE COUNTY MOUNTAINS-APPLE AND LUCERNE VALLEYS-COACHELLA VALLEY-SAN DIEGO COUNTY DESERTS- A monsoon air mass will remain in place across southern California today with scattered thunderstorms, mainly over the mountains, deserts, and Inland Valleys through this evening.
Monday afternoon and early evening, an unstable and still very moist atmosphere will produce slow-moving thunderstorms and heavy showers over the mountains and deserts. Thus, the flash flooding threat will remain high through early Monday evening, especially in recent burn areas.
The flash flood guidance values are three tenths of an inch of rainfall in 30 minutes for the new burn areas. Any thunderstorms in the burn areas could produce this amount of rainfall.
A flash flood watch means that conditions may develop that lead to flash flooding. Flash flooding is a very dangerous situation.
You should monitor later forecasts and be prepared to take action should flash flood warnings be issued.