Flash flood watch in effect as monsoonal thunderstorms hit parts of the Southland

Forecasters are predicting a chance of monsoonal showers and thunderstorms in areas of Southern California on Sunday night, with heavy rain having fallen already in the San Bernardino Mountains and the high desert.

Areas just south of Big Bear got 1.3 inches of rainfall Sunday, and there were downpours in the eastern Antelope Valley, meteorologists said. A flash flood watch was in effect until 10 p.m. Sunday in Los Angeles and Ventura county mountains, as well as the Santa Clarita and Antelope valleys.

“This is our monsoon season,” said Dan Gregoria, a meteorologist with the National Weather Service in San Diego. “But moisture levels are really high right now for this region.”

Some scattered showers — but fewer than on Sunday — will probably continue through at least Monday, especially in the mountains and deserts, according to the National Weather Service.

In Yucaipa, 10 miles east of San Bernardino, flooding and debris flows shut down Highway 38 near Angelus Oaks early Sunday morning, said California Highway Patrol Officer Jacob Grieda.

More than 20 cars were stuck in the mud overnight, and drivers were assisted by officers and CalTrans officials. That part of Highway 38 is expected to remain closed through at least Monday morning, Grieda said.

Hot and muggy weather is forecast to persist throughout the week in the Southland, with highs in the mid-80s closer to the coast and into the 90s for inland areas.