Flash floods sent water flowing into roads Thursday, triggering mudslides that forced the closure of a portion of Interstate 5 in the Tehachapi Mountains, a highway known locally as "the grapevine." California Highway Patrol said Friday night that I-5 had reopened after a cleanup.
On Friday afternoon, the northbound portion of the highway was reopened after street sweepers scoured mud from the road, the California Department of Transportation said on Twitter.
The southbound lanes, however, were still caked with mud, with clogged drains, on Friday afternoon, Caltrans said.
Some motorists fled on Thursday, while others sat trapped in cars and called 911 for help, according to Lisa Williams of the Los Angeles County Emergency Management.
Cars sat submerged in mud with their roofs barely visible. Hail the size of golf balls tumbled from the sky.
Nick Zernick became stuck on the mountainous highway known as "the grapevine" and saw a mudflow race down the road and envelope stalled vehicles, including his own. He posted videos on his Instagram account.
His seven-hour trip from San Francisco to Dana Point became a 20-hour journey because of the mudslide, said Zernick, an Orange County marketing consultant and real estate agent.
The experience was "super scary at first (be)cause it kept coming and we were next to some heavy rocks.... Some cars got really messed up by huge boulders," Zernick said.
Hail sizes were extraordinary.
"It's possible that someone could have lived in SoCal all of their lives and never have seen this size hail," said Joe Sirard, a meteorologist with the National Weather Service.
"If this area does see hail, it is the size of a dime," Sirard said. "Definitely no bigger than a quarter."
While rain is common in winter, the amount that fell is rare for October, he said.
Between 4 to 6 inches of rain fell in parts of Kern and Los Angeles counties, prompting floods that led to nearly a half dozen water rescues.
"The area is hilly along with canyons ... so the mud was created by the runoff ... and the debris flowing downhill," he said.
It's unclear how many people are stuck on highways.
Firefighters are trying to account for people stuck in vehicles and searching for those who may need help getting to a safe area, said Humberto Agurcia, a spokesman for the Los Angeles County Fire Department.
Searches are focused on the Lake Hughes vicinity and surrounding areas.
The Lake Hughes area is mostly rural and it's unclear if there are people stuck in homes. Rescuers said most calls for help have come from trapped drivers.
There have been no reports of injuries so far, authorities said.