The smoke spread across metropolitan Los Angeles to the coast and was visible from space in Weather Service satellite photos. The South Coast Air Quality Management District issued a smoke advisory and urged residents to avoid unnecessary outdoor activities in areas directly impacted by the smoke.
Jennifer Riedel, 43, anxiously watched as the orange-hued plume descended on her neighborhood in Azusa.
"I woke up from the rattling windows from the helicopters overhead, and I heard the police over the P.A., but I couldn't hear what they were saying," Riedel said. "I'm hearing from neighbors that we're evacuating, but I'm waiting for a knock on the door."
Riedel said her husband left for work early and she was getting her children, ages 5 and 7, ready to evacuate.
"They're a little nervous, but I'm keeping calm for them," she said. "I've been loading the car up with important papers and getting the kids dressed. We'll just take some essentials and get going if we have to."
The last catastrophic fire in the San Gabriel Mountains broke out in 2009 and burned for months. The flames blackened 250 square miles, killed two firefighters and destroyed 209 structures, including 89 homes.
About 70 miles to the northwest, a fire has burned at least one acre of tinder-dry chaparral near Pyramid Lake, said Los Angeles County Fire inspector Tony Akins. As many as 115 firefighters battled the flames and water-dropping helicopters were diverted from the fire in Glendora. The blaze started just after 11 a.m. east of Interstate 5 and involved a mobile home, which didn't appear occupied, Akins said. The cause was under investigation.
California is in a historically dry era and winter has brought no relief.
Red flag warnings for critical fire weather conditions were posted from Santa Barbara County south through Los Angeles to the U.S.-Mexico border, along the spine of the Sierra Nevada, and in areas east and north of San Francisco Bay.
Fires that struck windy areas of the state earlier in the week were quickly quashed by large deployments of firefighters, aircraft and other equipment before the flames could be stoked by gusts into major conflagrations.
Large parts of Southern California below mountain passes, canyons and foothills have been buffeted all week by the region's notorious Santa Ana winds.
Spawned by surface high pressure over the interior of the West, the Santa Anas form as the cold air flows toward Southern California, then speeds up and warms as it descends in a rush toward the coast. Some of the most extreme gusts reported by the National Weather Service topped 70 mph.
These offshore winds also raise temperatures to summerlike levels. Many areas have enjoyed temperatures well into the 80s.
California is also under the influence of a persistent upper-level ridge of high pressure anchored off its north coast that has also kept the region generally warm, dry and clear.
Associated Press Writer Christopher Weber contributed from Los Angeles.
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