Flood advisories issued for San Gabriel, Ventura County mountains due to heavy downpour

Forecasters have issued flood advisories for the San Gabriel and Ventura County Mountains, where excessive rainfall is expected.

The flood advisory for the San Gabriel Mountains will be in effect until 4:30 p.m. Sunday. There, "strong thunderstorms are developing, producing hourly rain rates of 1 inch," said the National Weather Service in a Tweet issued through its LA-area office.

"These rates will generate flooding of mountain roadways and low-lying areas," the NWS added. Residents in the area are advised to move away from recently burned areas.

Forecasters warn that the rain will likely trigger shallow mud and debris flows, minor rock falls, and flooding capable of localized damage, especially near burn scars and steep terrain. 

Elsewhere, thunderstorms were also recorded southeast of Acton in LA County and over Lockwood Valley in Ventura County around 1 p.m. Sunday. 

As a result, the NWS has also issued a flood advisory for the Ventura County mountains until 5 p.m., where flooding caused by excessive rainfall is expected. 

The NWS said in another Tweet that the storms will likely contain "heavy downpours with localized flash flooding, strong wind gusts, small hail, and dangerous lightning that could trigger grass fires."