"We have no choice but do to this," Santa Barbara Sheriff Bill Brown said. "It's not worth risking lives to avoid evacuation."
Because of the burn scars from recent fires in the area, flash flooding and significant debris flows remain a major concern. The National Weather Service in Los Angeles has issued a flash flood watch for these areas across Southern California until late Thursday night.
The amount of rain and the intensity are enough to cause flooding even without the impact of the recent fires. "We could experience localized flooding and road closures, which are not isolated to the burn areas. The threat of rock falls, mudslides and debris flow is high," said Rob Lewin, director of the Santa Barbara County Office of Emergency Management.
A large and powerful storm system across the eastern Pacific Ocean is expected to bring periods of moderate to heavy rain to portions of southwest California as early as Tuesday afternoon, continuing through late Thursday or early Friday.
The National Weather Service predicts rainfall rates between half to three-quarters of an inch per hour, with rain totals of 5 to 10 inches in the foothills and mountains. This total is significantly more than during the January 9 debris flow, when there was 3 to 6 inches across the region.
The mandatory evacuation in Santa Barbara County is effective at noon Tuesday for burn areas near the Thomas, Sherpa and Whittier fires. Those located in the Alamo burn area are in a recommended evacuation warning area.
Mandatory and voluntary evacuations will also take effect at noon Tuesday in Ventura County.