(CNN) -- Emergency officials in Orange County braced Saturday for a major storm expected to strike overnight in canyons near Los Angeles, while the bodies of three avalanche victims were discovered in mountains north of the city.
Preparations were in place for what could become the worst disaster since the October 2007 Santiago Fire, Orange County Fire Authority Mike Blawn told CNN.
That blaze scorched more than 27,000 acres and destroyed more than a dozen homes.
Voluntary evacuation orders were set early -- at noon "to allow people to take advantage of the daylight," Blawn said.
OCFA will have four urban search-and-rescue teams staffed throughout the storm, including a team positioned at the entrance to Santiago Canyon, he said.
A team of swift-water rescue experts has been added to the force, he said.
Based on forecasts from the National Weather Service, officials were preparing for up to eight inches of rain over nine hours on the southwest-facing slopes of Santiago, Modjeska, Williams, Harding and Silverado Canyons, Blawn said.
Santiago Canyon is the area's main canyon, while Modjeska, Williams, Harding, and Silverado Canyons are offshoots of Santiago.
Mudslides and shifting ground are a concern as is flash flooding from rain and mountain runoff, he said.
Blawn said officials from OCFA, the sheriff's department, Orange County Resources and Development Department and Orange County Emergency Service have worked together for months to prepare for such events.
A mandatory evacuation order was in place for large animals in Santiago Canyon. Such orders typically coincide with voluntary evacuation orders.
An OCFA bulldozer is on call in Yorba Linda, on the other end of Santiago Canyon from where the urban search-and-rescue team is positioned, Blawn said.
OCFA also has a helicopter on standby for possible aerial search and rescue missions from dawn to dusk on Sunday.
Three OCFA Incident Management Teams are on call should a major response be needed.
Meanwhile, the bodies of three men missing since Friday were discovered in an avalanche site in Los Angeles County, a sheriff's spokesman said Saturday.
But another person -- who had also been reported missing -- walked off the mountain near the Mountain High Ski Resort in Wrightwood, California, after spending the night in the forest, Los Angeles Sheriff's Department Deputy Luis Castro said.
He was examined at a hospital and released.
All four had been missing since Friday afternoon, Castro said. The three victims -- one in his 20s, one in his 30s and one in his 60s -- were guests at the resort who had strayed from the 290 acres of resort property, said John McColly, a spokesman.
"They were out of bounds in canyons neighboring the resort," he said. "Everything in bounds is safe and groomed and protected." The deaths occurred in three separate avalanches, he said. E-mail to a friend