Heat, moisture trigger thunderstorms and hail

Intense heat seared much of Southern California for a fourth day Thursday as subtropical moisture triggered thunderstorms that caused torrents of water to push mud and softball-sized rocks across roadways and block one of the state's main north-south arteries.

As inland areas baked under triple-digit temperatures, firefighters from Menifee in Riverside County to Tehachapi in Kern County responded to multiple small brush fires, officials said. Thunderstorms also dropped hail in San Jacinto and Menifee.

But the worst of the weather struck along U.S 395 in Inyo County.

A strong afternoon thunderstorm barreled through the area, causing a 4-foot wall of mud to block both lanes of the highway near the Coso Junction area, about 130 miles north of Los Angeles, according to witnesses and the California Highway Patrol.

“It just rained and rained. It just came down hard,” said Jerry Swab, who works at the Coso Junction Ranch Store, where stranded motorists were waiting Thursday afternoon for crews to clear the highway. The closure backed up traffic on the highway for several miles.

The powerful downpours also caused havoc on California 190 southwest of Owens Lake, where mud and softball-sized rocks were strewn across the roadway for about a mile, the CHP said. The agency said that motorists stopped to help clear some of the debris.

In Riverside County, firefighters responded to three small brush fires in Borel and Menifee. One of the blazes, fanned by erratic winds, burned 11 acres before it was knocked down by 55 firefighters who were aided by two copters and four air tankers, the Riverside County Fire Department said.

A blaze near Tehachapi scorched 55 acres and briefly threatened homes near Tucker and Highline roads before it was brought under control by about 30 firefighters, the Kern County Fire Department said.

--Robert J. Lopez

Photo: As thunderclouds build in the background, Don Spencer angles for Bass at Irvine Lake in Orange County. Credit: Allen J. Schaben  / Los Angeles Times