Driving Rain, Squalling Commuters : Storm: More than 4 inches fall in the latest outburst, causing mudslides, flooded streets and widespread traffic jams. And it isn’t over yet.

A driving storm dumped more than 4 inches of rain in Orange County on Thursday, causing mudslides, slick pavement and flooded streets that resulted in traffic nightmares for commuters.

Up on Santiago Peak, the county’s highest mountaintop at 5,687 feet, 4.65 inches of rain fell during a 24-hour period from early Wednesday to Thursday morning, said William Reiter, county public works operations manager.

“It’s the most we’ve had on the peak in any one rainstorm since the drought began,” said Reiter, whose division kept the county’s storm-watch center open all day Thursday “as a precaution.”

The storm also spawned the county’s first tornado since 1977, damaging more than 50 homes in Irvine. One man was injured there when a eucalyptus tree fell on his car. Irvine police said he had only minor injuries.

The Santa Ana River was a foot deep, the highest in recent years, and slides closed traffic in Carbon Canyon in Brea, Silverado Canyon and along Ortega Highway. Crews were out sandbagging for local flooding and handling the slides, but county flood control officials reported no major problems.

“We weathered the day reasonably well,” Reiter said. “Our crews have been unplugging drains, and watching the Santa Ana River which only has minimal flow. We had no major erosion or slides.”

But officials closed Ortega Highway in both directions from La Pata Avenue to Lake Elsinore about 8 p.m. until further notice due to mudslides and flash floods.

The rain hindered a repair crew dispatched to a ruptured 6-inch water main in Santa Ana that caused the road to cave in and created a 15-by-20-foot hole on 1st Street during morning rush-hour traffic.

With the rain coming down in sheets, “we can’t pour the blacktop on right now until we have a break in the rain,” a repair crew supervisor said. One lane was closed.

A third, less-intense storm is expected to arrive this morning and linger through the weekend, bringing intermittent showers, said Stephen Burback, a meteorologist with WeatherData Inc., which provides forecasts for The Times.

Rain may be heavy at times this morning with a chance of thundershowers, ending later in the day, Burback said. It is expected to be partly cloudy through Saturday, with highs today in the upper 50s to low 60s, rising to the low- to mid-60s on Saturday.

“You can expect about an inch to an inch and a half more of rainfall in the coastal areas and from 2 to 3 inches in the mountains,” he said.

“It’s going to be pretty much continuous,” Burback said. “I don’t see any real clearing, or dry period, until Tuesday.”

Rough seas, thunderstorms and strong south-to-southwest winds of 15 to 25 knots are also expected from Point Conception to the Mexican border.

Thursday’s high winds and driving rain caused problems throughout the county, especially in coastal areas.

Storm-driven surf and a high tide combined to pitch water over the seawall at the west jetty in Dana Point, leading the Sheriff’s Department to order beach walkways closed to pedestrians.

In Newport Harbor, the Sheriff’s Harbor Patrol spent Wednesday night and Thursday morning reattaching lines to private pleasure boats blown out of their moorings. Two small boats--a 20-foot skipjack and a 14-foot sailboat--had taken on water from cracked hulls and were sinking, Olson said.

“When it starts to blow out there in Newport Beach, it really raises a lot of problems and havoc. Those docks really take a beating,” said Sheriff’s Lt. Richard Olson.

On the roads, the California Highway Patrol reported 68 weather-related accidents--15 with injuries--before 2 p.m. The CHP reported 20 cars stalled on Orange County freeways

Lanes were closed due to flooding on a number of freeways throughout the county. The Costa Mesa Freeway was flooded from the Santa Ana Freeway interchange just north of 17th Street in Santa Ana, the Riverside Freeway was reported flooded in several locations in Anaheim, including Imperial Highway near Kraemer Boulevard and Euclid Avenue, and the Santa Ana Freeway was flooded at the Laguna Freeway.

Thunderstorms and strong winds also wreaked havoc with crops in the county, said Nancy Jimenez, executive director of the Orange County Farm Bureau. Jimenez said the rain heavily damaged outdoor bedding plants at wholesale nurseries and 100 acres of strawberries.

Near Brea, eastbound Carbon Canyon Road was closed east of Valencia Avenue after a series of mudslides that started about midnight, said Brea Police Lt. Chester Panique. A section of the road was closed at 2:15 a.m. on Thursday, he said.

In Huntington Beach, the storm caused scores of power failures over the past two days, city officials said. They also reported a rash of flooded streets and several calls from anxious residents concerned about rising drainage channels.

Jack Ellis, maintenance supervisor in the city’s Public Works Department, said Thursday that despite some residents’ worries, drainage channels are flowing smoothly and no flooding is expected from them. He said that some drainage outlets, notably the Wintersburg Channel in northwest Huntington Beach, had some backup early Thursday because of high tides.

Ellis said the power outages contributed to flooding Wednesday night and early Thursday on some streets in the city. The loss of power in some parts of the city kept electric water pumps from operating, he said.

The rainfall at the Los Angeles Civic Center was 2.44 inches in the 24-hour period that ended at 4:30 p.m. Thursday.

Runoff from the heavy rain caused a 2-million-gallon overflow of partially treated sewage in Ballona Creek, which empties into the Pacific Ocean at Marina del Rey, forcing the closure of beaches all along the Los Angeles coastline.

City officials estimated that up to 15 billion gallons of polluted water from sewers and storm drains had entered Santa Monica Bay, an unusually large amount, even in a major storm. They attributed that to the long dry spell, which caused storm drains to fill with toxic chemicals and organic pollutants.

In Ventura County, 5 to 8 inches of rain fell in the mountains north of Ojai, with 2 to 4 inches recorded in most other areas. The single day of rain was the county’s heaviest since 2.84 inches fell in the city of Ventura on Valentine’s Day, 1986, officials said.

Heavy snow was reported in the Southland mountains as low as 5,500 feet. The Big Bear area in the San Bernardino Mountains had more than 6 inches on the ground. Similar amounts were reported in the San Gabriel Mountains with more expected from the new storm.

In San Diego, the storm ripped away a nylon canopy above the new San Diego Convention Center, cut off power to more than 39,000 homes, sent rocks sliding onto highways, brought hail to some areas and spawned a waterspout over the ocean.

Times staff writer Bill Billiter contributed to this report.

A STRANGE TWIST: Tornado’s touchdown in Irvine leaves 50 homes damaged. A1

Storm’s Rainfall Figures* Total number of inches of rain that have fallen since the storm began on Wednesday. Fullerton: 3.19 inches Yorba Linda: 3.43 inches Cypress: 3.03 inches Huntington Beach: 2.56 inches Anaheim: 3.31 inches Santa Ana: 2.99 inches San Juan Capistrano: 3.27 inches Silverado Fire Station: 4.02 inches *As of 9 p.m. Thursday* Source: WeatherData Inc.