Update, 5:30 p.m. Monday
The Santa Barbara County Sheriff’s Office has issued a mandatory evacuation order for individuals below last year's wildfire burn areas, effective at noon Tuesday.
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With possibly “the most powerful storm of the season since the Jan. 9 debris flow” approaching Santa Barbara County, emergency officials have issued a pre-evacuation advisory for communities below recent wildfire burn areas.
“The National Weather Service forecast indicates there is the potential for a prolonged period of moderate to heavy rainfall with this system, with highest rainfall intensities expected to occur sometime between late Tuesday night … through early Thursday,” according to the advisory issued on Saturday by Santa Barbara County’s Office of Emergency Management.
“During this time, rainfall rates will likely exceed U.S. Geological Survey thresholds, and bring the threat of significant flash flooding and debris flows in recent burn areas.”
“Impact areas need to prepare for the possibility of an evacuation for Tuesday through Thursday,” according to the county’s advisory.
The latest forecast indicated rainfall rates are likely to be in the range of 0.5 to 0.75 inches per hour, officials said.
Communities potentially affected by the storm are below the Thomas, Whittier, Sherpa and Alamo fire burn areas.
“Based on today’s forecast from the National Weather Service, this is the most powerful storm of the season since the Jan. 9 debris flow,” said Rob Lewin, county emergency management director. Mudslides on Jan. 9 killed 21 people in Montecito.
A large upper-level low-pressure system off the coast is expected to merge with a second low-pressure system Tuesday night and Wednesday, according to the National Weather Service in Oxnard.
Forecast models agree that “there will likely be plenty of rain over Southern California between Tuesday night and late Thursday night,” the NWS said in its forecast discussion.
“During the heaviest rains, it will be possible to see 3-hour rainfall up to 1 to 2 inches in some areas,” the NWS said.
According to the NWS, SLO County will see its heaviest rain Tuesday night.
There will also be the potential for widespread urban and small stream flooding throughout the region, and rockslides in the susceptible areas.