Santa Ana winds bring dangerous fire conditions, trigger red flag warnings in South California

Red flag warnings are in place for Southern California due to Santa Ana winds that will bring gusts up to 65 mph and “extremely rare and dangerous” fire weather conditions.

Red flag warnings are in place Monday from 10 a.m. through Wednesday 6 p.m. local time for the San Gabriel Mountains, Santa Monica Mountains, Santa Clarita Valley, Ventura County coasts and valleys and western San Fernando Valley, the National Weather Service office in Los Angeles said.

Meanwhile, a "particularly dangerous situation" red flag warning is also in place from 10 p.m. Monday through 2 p.m. Tuesday in those same areas due to Santa Ana winds, low humidity and extremely dry vegetation. The warning impacts Los Angeles and Ventura counties.

This rarely issued warning means there's a high risk of "extreme fire behavior and very rapid growth."

Santa Ana winds occur when air from a region of high pressure over dry desert flows westward toward low pressure areas off the California coast, and are more common from September through May. Under the PDS red flag warning, damaging wind gusts of 60 to 80 mph will be likely along with single digit humidities across windier mountains and foothills.

Along most wind-prone coastal and valley areas in Los Angeles and Ventura counties, gusts of 40 to 65 mph are forecast. 

Santa Ana winds are forecast to increase late Monday morning into the afternoon and peak Monday night into Tuesday, the NWS said.

Offshore winds will diminish a bit by Wednesday. It’s expected be a long duration red flag event due to the “strong likelihood of widespread single digit humidities,” the Sunday evening advisory said.

With the threat of damaging wind gusts, there will be an increased risk for downed trees and power lines as well as power outages. 

Forecasters warned to expect hazardous driving conditions and travel delays, particularly on Tuesday morning.

Some of the highest wind areas will likely be the San Gabriel Mountains, Santa Susana Mountains, western Santa Monica Mountains into Malibu, Ventura County valleys, and western San Fernando Valley, particularly the Highway 118/210 corridors from Porter Ranch to San Fernando.Forecasters warned that there's potential for new fire ignitions to have "very rapid fire spread" and "extreme fire behavior," including long range spotting.

"As a result, there is the increasing threat for fire weather conditions to rival other historical fires in recent times including the Mountain and Thomas Fires," the weather service warned.

Southern California Edison, a utility company, warned on its website that there may be public safety power shut-offs “to protect communities.”