100MPH Gusts Expected In 'Most Destructive' Windstorm In A Decade

LOS ANGELES, CA — The windstorm blowing into Southern California is expected to be the strongest to batter the region in more than a decade, creating extreme fire risk even as portions of the region are blanketed in drizzle and snow.

The extreme weather prompted power shutoff warnings, school and road closures and has firefighters and residents on edge. One of the most powerful Santa Ana events in more than 10 years, the windstorm also comes amid one of the driest years on record, making Southern California a tinderbox. The region is experiencing the driest start to the rainy season on record.

Wind gusts in the afternoon Tuesday are expected to reach 80 mph with isolated gusts in mountains, canyons and foothills topping 100 mph, according to the National Weather Service. Gusts that powerful can down power lines, jackknife big rigs, trailers, and motorhomes, and turn spot fires into raging wildfires. Strong offshore gusts will also bring dangerous conditions off the coasts of Orange and Los Angeles counties, including Catalina Island, and potential delays and turbulence could arise at local airports.

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Even as red flag warnings took effect at 4 a.m. Tuesday, the California Highway Patrol responded to reports of a series of brush fires near freeway homeless encampments from the I-10 in Los Angeles and the Ventura (101) Freeway to the Santa Ana Riverbed in the Inland Empire.

The San Bernardino Mountains started the day Tuesday with a dusting of snow, and inland communities saw light drizzle even as small brush fires broke out, reflecting just how bone-dry vegetation has been this season.

Public safety power shutoffs are being considered for nearly 500,000 customers across the region, according to Southern California Edison’s website.

SEE ALSO: These Areas Are At Risk Of SoCal Public Safety Power Shutoffs

The upcoming winds will act as an “atmospheric blow-dryer” for vegetation, bringing a long period of fire risk that could extend into the more populated lower hills and valleys, according to Daniel Swain, a climate scientist with the University of California, Los Angeles and the National Center for Atmospheric Research.

“We really haven't seen a season as dry as this one follow a season as wet as the previous one,” Swain said during a Monday livestream. “All of that extra abundant growth of grass and vegetation followed immediately by a wind event of this magnitude while it's still so incredibly dry," elevates the risk.

Red flag warnings of critical fire danger took effect at 4 a.m. Tuesday and remain in place until 6 p.m. Thursday for the Malibu coast, the Santa Monica Mountains Recreational Area, the San Gabriel Valley, the San Fernando Valley, Calabasas, the Santa Clarita Valley, the San Gabriel Mountains, and the Golden State (5) and Antelope Valley (14) freeway corridors.

"Residents across Southern California are urged to remain vigilant and monitor the latest forecasts," the National Weather Service advised. "There is high confidence in strong offshore winds with the potential to be the strongest wind event of the season, especially for the Southland valleys. Trees, large tree branches, and power lines may be downed by the wind ... Residents living the near the foothills and mountains are advised to review the `Ready, Set, Go!' fire plan. Most residents should be in the `Set' stage and being prepared to go in the event of the fire evacuation."

At noon Tuesday, the warning will extend to include Los Angeles County beaches, the Palos Verdes Hills, Catalina Island and the inland Los Angeles County coast, stretching into downtown Los Angeles.

The red flag warning will be in place from 10 a.m. Tuesday to 6 p.m. Wednesday in the Antelope Valley and Antelope Valley foothills.

The warnings will be upgraded to "particularly dangerous situation" red flag warnings -- noting extremely critical wildfire conditions -- from noon Tuesday to 4 p.m. Wednesday for L.A. County beaches, the coastal area stretching into downtown, the Malibu Coast, the Santa Monica Mountains Recreational Area, the San Fernando Valley, San Gabriel Valley, San Gabriel Mountains and the Antelope Valley (14) Freeway corridor.

The Santa Monica-Malibu Unified School District announced it was closing all Malibu schools Tuesday due to dangerous weather conditions but that Santa Monica schools remained open.

In Orange County, a red flag warning will be in place from 1 p.m. Tuesday through 6 p.m. Thursday for the Santa Ana Mountains and inland parts of the county, including a "particularly dangerous situation" from 7 a.m. to 1 p.m. Wednesday. Orange County coastal areas will be under a red flag warning from 4 p.m. Tuesday to 6 p.m. Wednesday.

"A very strong, widespread, and destructive north to northeast windstorm will bring Extremely Critical fire weather conditions to many areas of Los Angeles and eastern Ventura counties Tuesday afternoon into early Wednesday afternoon," according to the NWS. "This is a PARTICULARLY DANGEROUS SITUATION (PDS) Red Flag Warning event in many areas, with the combination of very strong upper level wind support, tightening offshore pressure gradients and moderate cold air advection.

"The strongest winds with this event are expected to be Tuesday afternoon into early Wednesday afternoon when widespread damaging wind gusts of 50 to 80 mph are likely," forecasters said. "The San Gabriel mountains, Santa Susana mountains, and foothills of the San Gabriel/San Fernando Valleys will likely see areas of destructive wind gusts between 80 and 100 mph. ... The strong winds will likely result in widespread downed trees/power lines, as well as widespread power outages."

Forecasters said the event "will likely be the most destructive windstorm seen since 2011 windstorm that did extensive damage to Pasadena and nearby foothills of the San Gabriel Valley. Any communities along Highway 118 and 210 corridors will be at highest risk for comparable wind damage."

Forecasters warned particularly of the possibility of "breaking mountain waves."

"These occur when very strong winds aloft intercept mountain tops at nearly perpendicular angles which will happen with these events," according to the NWS. "These short lived and very difficult to predict events can cause considerable local damage wherever they occur. The most likely areas for this phenomena are the eastern San Fernando Valley and the northern San Gabriel Valley."

Humidity levels are also expected to drop, most notably on Wednesday, creating dry conditions that could amplify the fire danger.

Forecasters said that despite the Santa Ana winds, temperatures across the region could actually fall by 5 to 10 degrees on Tuesday due to the amount of cold air accompanying the system. But the temperatures will bounce back on Wednesday, recovering those 5 to 10 degrees.

Due to the elevated fire danger, Caltrans will close Topanga Canyon Boulevard between Mulholland Drive and Pacific Coast Highway from 10 a.m. Tuesday through 6 p.m. Friday. Only residents and local business traffic will be permitted into the canyon during the closure.

According to the Los Angeles Unified School District, Topanga Elementary Charter School, which is located just off Topanga Canyon Boulevard, will be closed on Tuesday, and all students were instructed to report instead to Woodland Hills Academy at 20800 Burbank Blvd.

Fire departments across the area are expected to pre-position resources so they can quickly respond if brush fires erupt. Officials with Cal Fire said the agency was moving resources from Northern California to Southern California, including 45 engines and six hand crews that will be stationed in the region, including Los Angeles and Orange counties.

Cal Fire Chief Joe Tyler reminded residents that 95% of wildfires are human-caused, and he urged vigilance.

"As we experienced in Ventura County in November with the Mountain Fire and again in December with the Franklin Fire in Malibu, wildfire is a year- round threat," Tyler said in a statement. "Please be vigilant and don't be the cause of the next wildfire in your community."

NWS officials warned residents to be prepared for the possibility of downed trees and power poles and hazardous driving conditions, particularly for big rigs and other high-profile vehicles. The winds could also result in air travel delays and turbulence. Forecasters also advised residents to stay away from windows and trees once the winds start, park cars away from trees, and to prepare for possible power outages by charging all electronic devices ahead of time and ensure generators are prepared.

As is standard during high-fire-danger conditions. Southern California Edison customers in some areas could have their power turned off under the utility's Public Safety Power Shutoffs program. The program is designed to de- energize power lines that could potentially be damaged and spark a wildfire during red flag conditions. According to SCE's website, more than 70,000 customers in Los Angeles County and more than 9,400 in Orange County are under consideration for power shutoffs during the upcoming wind event.

Updated information about power cuts is available at https://www.sce.com/outage-center/outage-information/psps.

The city of Los Angeles will impose red flag parking restrictions at 8 a.m. Tuesday, continuing until further notice, likely for the duration of the wind event. The restrictions are designed to keep streets clear for emergency vehicles that may need to quickly access developing wildfires, and to ensure open roadways for residents who may need to evacuate.

The South Coast Air Quality Management District, meanwhile, issued a windblown dust advisory that will be in effect from 10 a.m. Tuesday until 6 p.m. Wednesday, noting that the strong winds could lead to unhealthy air quality in areas of Los Angeles, Orange and Riverside counties.

City News Service and the Associated Press contributed to this report.