Santa Barbara County authorities ordered mandatory evacuations Monday for residents below fire-ravaged mountains ahead of a "fast-approaching" storm that could cause flooding and mudflows.
"Those hills are filled with silt, with rocks, with boulders, there's plenty more up there that could come down," Sheriff Bill Brown told reporters Monday, adding that conditions may be more precarious than in January, before deadly mudslides swept through Montecito. "Don't be fooled into thinking that this can't happen again."
Residents who live in areas at "extreme risk" for debris flows near the Thomas, Sherpa and Whittier burn areas were ordered to leave by 8 p.m.
Authorities recommended that those in "high risk" areas leave also, as they face the risk of flooding or being cut off from services and utilities. People with limited mobility or large animals should consider leaving immediately, officials said.
County officials created an interactive map so residents can determine the level of risk to their neighborhoods.
Authorities will go door-to-door to notify residents of the order, but they will not be able to alert everyone in person.
"It is very important that you spread the word about this evacuation — tell your family members, tell your friends, tell your neighbors," Brown said. "Please do not wait for someone to come to your door."
A voluntary evacuation order was issued in Ventura County for residents of Matilija Canyon and North Fork.
Rain will begin to fall Monday evening, but the heaviest downpour is expected in Santa Barbara and western Ventura counties Tuesday from 7 a.m. to 1 p.m., said Kathy Hoxsie, a meteorologist with the National Weather Service.
That's when the region could see rainfall rates that exceed half an inch per hour, an amount that could trigger debris flows. A slight chance of a thunderstorm means some areas could see seven-tenths of an inch of rain an hour.
"The problem with all of these storms is they're somewhat like a shotgun blast — you can't predict with complete accuracy where they're going to hit most intensely," Brown said.
Even so, Tuesday's storm is expected to be more powerful than the March 2 storm that triggered widespread evacuations, but caused little damage, he said.
"This one, the weather service had much greater concern," Brown said.
An evacuation center was opened at the Goleta Valley Community Center at 5679 Hollister Ave.
The storm will dump heavy rain from eastern Ventura County to downtown Los Angeles beginning at about 11 a.m., officials said.
Montecito is still recovering from devastating mudflows that swept away homes and killed 21 people.
8:55 p.m.: This article was updated with statements from a news conference.