Red flag fire warnings, high winds in LA County forecast

High winds will be picking up across most of the Southland Tuesday evening, building overnight to levels high enough to prompt a red flag warning of critical fire danger that will be in effect throughout the day Wednesday.

A high wind warning is set to take effect at 7 p.m. Tuesday and remain in force until 7 p.m. Wednesday in the Los Angeles County Mountains, Santa Clarita Valley, San Fernando Valley, Santa Monica Mountains and the Malibu coast.

Gusts of up to 65 mph could pound mountain and some valley areas, according to the National Weather Service. Isolated gusts of up to 75 mph are possible in the western Santa Monica Mountains, forecasters said.

A less severe wind advisory will be in effect from 10 p.m. Tuesday until 7 p.m. Wednesday in the San Gabriel Valley. Forecasters said foothill areas could see winds of 20 to 30 mph, with gusts up to 50 mph.

High wind warnings will also be in effect through Wednesday night in Orange County inland areas, Santa Ana Mountains. A wind advisory will be in effect for Orange County coastal areas.

“Damaging winds will blow down large objects such as trees and power lines,” the weather service warned. “Power outages are expected. Travel will be difficult, especially for high profile vehicles.”

“People should avoid being outside in forested areas and around trees and branches,” the agency added. “If possible, remain in the lower levels of your home during the windstorm, and avoid windows.”

The windy conditions, combined with anticipated low humidity, prompted the NWS to issue a red flag warning that will impact most of western Los Angeles County from 7 a.m. to 7 p.m. Wednesday.

“Strong high pressure building into the Great Basin will likely support the first strong Santa Ana event of the season tonight (Tuesday) into Wednesday focused across western Los Angeles County into much of Ventura County,” according to the NWS. “The wind-prone coastal and valley areas will likely see peak gusts in the 40 to 60 mph range, and the Los Angeles County mountains will likely see gusts of 55 to 75 mph. Relative humidity will likely remain above critical values through tonight, with minimums of 15% to 25%. Additional drying is expected Wednesday morning into the afternoon with minimums as low as 6% to 12%. Gusty and potentially damaging winds combined with very low humidity will likely support at least 6 hours of critical fire weather across much of Los Angeles and Ventura Counties.”

Besides the LA County Mountains, areas covered by the red flag warning include the Santa Clarita and San Fernando valleys, the Malibu coast and the Santa Monica Mountains. The red flags also extend to much of Ventura County.

Colder conditions will also bring low relative humidity numbers — in the 8% to 18% ranges to the LA County Mountains — that can be more conducive to fire conditions, the NWS said.

“If fire ignition occurs there could be rapid spread of wildfire that would lead to a threat to life and property,” according to the weather service.

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