Downpour pounds Southland

An out-of-season storm lashed Southern California with thunderous squalls Saturday and wreaked havoc across the region, trapping cars in mud, sending so much polluted water to the coast that officials warned people not to go into the ocean, and contributing, officials suspect, to traffic accidents that killed at least five people.

Small floods formed sporadically throughout the day, including one in Costa Mesa that forced a woman to scramble atop her van while she waited for help.

The rare storm, the product of a low-pressure system known as an “orphan,” moved out of the area Saturday night. According to the National Weather Service, more typical weather for the season is expected today, with temperatures in the 70s and clear skies in sharp contrast to the chaos that erupted at times on Saturday.

In perhaps the most dramatic incident, mud, ash and debris swept down hillsides near the west end of Griffith Park, overflowing a clogged drainage basin, oozing across Forest Lawn Drive and trapping 14 vehicles.

Most vehicles were parked and unoccupied at the time, though several drivers got stuck while stopped at red lights. Witnesses described a frenzied scene, with lava-like goop seeping down the hills and victims -- including several people still in their yoga gear after being rousted from an exercise class -- racing to their cars to try to escape.

The muck eventually covered two sections of Forest Lawn Drive, a heavily used route between the lower San Fernando Valley and Hollywood. There were no injuries. It took five hours to free all of the cars, and the road was still closed to non-local traffic at nightfall, as front-end loaders scraped away debris.

Another group of drivers was temporarily trapped by the debris in a nearby parking garage. The mud also seeped into the first floor of three Oakwood Garden apartment buildings.

Authorities linked the slide to a March fire that consumed 160 acres above the Warner Bros. Studio and Forest Lawn cemetery and filled the drainage basins below with foliage, ash and other debris. Heavy rainfall then pushed the debris over the edge of the basin into the roadway.

Mark Skully, one of the trapped motorists, was headed to his Sunland home to meet his wife and had stopped at a light when mud and other debris swept across the road beneath his pickup and left him stuck.

“A mudslide,” he said, after a tow truck pulled him out, “will really screw up your plans.”

The storm, meanwhile, sent water containing animal droppings, oil, fertilizer, pesticides and the like cascading through storm drains. As a result, the Los Angeles County Department of Public Health warned the public to avoid ocean water until Tuesday evening.

The pollutants could cause bacteria levels to rise significantly near drains, creeks and rivers. Ingesting bacteria by going into the ocean could cause diarrhea, fever and stomachache.

“You could get sick,” said Eric Edwards, chief of the department’s water quality program. “We’re not saying you will. But you could.”

It takes about three days for “everything to return to normal,” Edwards said.

Officials were investigating the storm’s role in at least three fatal traffic accidents.

Late Friday night, as the heavy rain began, a 52-year-old San Jose woman was killed in the Santa Susana Pass northwest of Chatsworth. The woman was riding in a Ford that was headed west on Highway 118 when the driver struck a BMW that had previously crashed and was partially blocking the road. When a third car struck the Ford, the woman was ejected and killed.

The woman, who was not identified, was not wearing her seat belt, according to a CHP report.

About 8 a.m. Saturday, a 37-year-old man died after losing control of a white moving truck in heavy rain on Interstate 15 in Mira Loma. The truck crashed into the center divider and flipped onto its side, ejecting the man, who was not wearing a seat belt.

Three hours later, a 22-year-old woman, a 15-year-old girl and a baby boy were fatally injured and a 26-year-old man critically injured when two vehicles collided head-on in the rain on Highway 330, a winding mountain road in San Bernardino County.

The four were traveling in a Subaru when the car crossed into oncoming traffic as the driver tried to negotiate a curve, striking a Chevrolet. The four men in the Chevrolet suffered minor injuries.

Officials closed the highway between San Bernardino and Running Springs for about five hours.

The storm generated the Southland’s first significant rainfall since April.

According to the National Weather Service, half an inch to an inch of rain fell on most of Los Angeles and eastern Ventura counties since late Friday. Downtown Los Angeles and Santa Monica had received about half an inch, Burbank an inch and Pasadena an inch and a half by Saturday evening.

Several measuring stations, including those at the Los Angeles, Burbank and Santa Barbara airports, recorded record rainfall for this time of year.

The bursts of rain caused sporadic flooding throughout the region.

About 5:30 a.m. Saturday, several vehicles got stuck in floodwater on the 110 Freeway just north of the 91 Freeway, forcing the temporary closure of four southbound lanes.

Perhaps the worst flooding was reported in Orange County, where more than an inch of rain fell in some areas.

In Costa Mesa, a woman had to be rescued early Saturday from atop her van in about 5 feet of water. She had attempted to drive through a flooded stretch of road near West 17th Street and Pomona Avenue.

“When we got there, the water had risen to the window level and she was standing on top,” said Costa Mesa Police Lt. Dale Birney. “She could have been in danger if she’d tried to stay in the van.”

A firefighter waded through the water and helped the woman to safety.

In Anaheim, the Angels’ regionally televised baseball game against the Seattle Mariners was delayed for nearly an hour by a short but powerful downpour. The rain came about half an hour before the scheduled 12:55 p.m. start and sent fans scurrying up the aisles for cover.

The downpour appeared to catch the grounds crew by surprise and drenched the uncovered infield. Not that the crew has had much practice covering the field; the delay was believed to be the first at Angels Stadium since opening day 1998. There hasn’t been a rainout there since June 16, 1995.

The storm also caused scattered power outages.

About 30,000 Los Angeles Department of Water and Power customers were without power at the peak of the storm.

Nearly 5,000 were still without power as of 9:30 p.m. Saturday.

About 1,000 Southern California Edison customers were without power at 8:30 p.m., mostly in Lynwood, Gardena, Torrance, South Gate, Manhattan Beach, Rancho Palos Verdes, La Mirada, Ontario, Upland, Twentynine Palms and Pearblossom, said spokeswoman Mashi Nyssen. Customers are asked to call SCE at (800) 611-1911 or police or fire authorities if they encounter downed power lines.

In some parts of Los Angeles County, the storm was not as bad as feared.

On South Lake Avenue in Pasadena, the rain had little effect aside from soaked sidewalks and streets lined with raindrop-speckled cars.

Cafe staffs put out tables Saturday morning with paper tablecloths, and the sun was already peering through the clouds as people ventured out for exercise or a morning caffeine fix.

“I’m always amazed at how people here make such a big deal about the tiniest amount of rain,” said Michael Harpster, a 64-year-old native New Yorker who was reading a newspaper outside a Starbucks. “I start hearing my friends ask: ‘How am I going to drive?’ Or: ‘Do I really need an umbrella?’ ”

Harpster, who has lived in Pasadena for five years, said he stayed in his apartment Friday night, when the worst of the storm hit his area.

“I’m happy the rain came, as it’s needed,” he said. “But I’m happier now that it’s gone.”

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scott.gold@latimes.com

ron.lin@latimes.com

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Times staff writer David Haldane contributed to this report.