A flash flood watch was in effect for parts of Los Angeles County Monday, stretching through this evening, the National Weather Service said.
The watch affected the L.A. County Mountains, excluding the Santa Monica Range; the San Gabriel Valley; and the Antelope Valley.’
The NWS said areas likely to be impacted included Lancaster, El Monte, East Los Angeles, Topatopa Peak, Reyes Peak, West Covina, Alhambra, Falling Springs, Pasadena, Pomona, Palmdale and Whittier.
Scattered showers and thunderstorms — some capable of producing heavy downpours, with rainfall rates up to an inch per hour — are possible, the NWS said.
Locations most susceptible to flash flooding include those in and below recent burn areas, including the Bobcat, Dam, Ranch2, and Lake burn areas. Shallow mud and debris flows capable of producing localized damage are possible in and below these burn areas, the weather service said.
A flash flood watch means that conditions may develop that lead to flash flooding. The NWS advised residents of affected areas to remain alert and follow directions of emergency preparedness officials.
More information from the usgs on debris flows and their impacts can be found at landslides.usgs.gov/research/wildfire/.