By Alex Dobuzinskis
LOS ANGELES (Reuters) - Road crews cleaned up on Friday after mudslides that swept parts of Southern California and left a major highway closed for a second day, as forecasters warned of possible thunderstorms that could trigger additional flash floods going into the weekend.
Heavy rains on Thursday sent tons of mud streaming onto Interstate 5 along the Grapevine mountain pass about 50 miles north of Los Angeles, shutting down the region's main north-south highway, California Department of Transportation (Caltrans) officials said.
The interstate segment remained closed on Friday morning as crews swept the road surface of mud and other debris while clearing drainage culverts along the highway, Caltrans spokeswoman Lauren Wonder said.
Authorities hoped to reopen the Grapevine section later in the day, once geologists had a chance to survey a key hillside in the area to check its stability, she said.
"Anytime you've got a major interstate closed it's a big deal. That's a big truck route," Wonder said. "We're working as fast as possible."
On Thursday, trucks and cars stranded on the highway by mud had to be towed off the interstate, she said.
The Leona Valley, about 20 miles north of Los Angeles, saw the greatest downpours on Thursday, with 3.58 inches of rain falling - most of that in a 30-minute period - and golf ball-sized hail thrown into the mix, said National Weather Service meteorologist Robbie Munroe.
Elsewhere in Southern California several roads were washed out and there were reports of motorists having to be rescued from torrential flooding in northern Los Angeles County, he said.
Also on Thursday, two dozen people were forced to take shelter in an elementary school from flash flooding in an area 14 miles west of the high desert town of Lancaster, Munroe said.
A flash flood watch remained posted through Friday evening, advising of storm conditions that could unleash flash flooding in several mountain areas and in northern Los Angeles County's Antelope Valley, which bore the brunt of flooding on Thursday.
There was a slight chance of thunderstorms returning to the region on Saturday and Sunday, Munroe said.
(Reporting by Alex Dobuzinskis; Editing by Steve Gorman and Mohammad Zargham)