LOS ANGELES _ A wildfire in the Santa Clarita Valley area has scorched more than 11,000 acres, prompting new evacuations Saturday afternoon for hundreds of homes in the area, authorities said.
The evacuation order was issued about 3:15 p.m. for residents in Sand Canyon, extending from Robinson's Ranch Golf Course up to Bear Divide, according to the Los Angeles County Fire Department. All residents in Placerita Canyon, from the Nature Center to Sand Canyon, have also been ordered to evacuate.
At least 1,500 homes are threatened, fire officials said.
The Sand fire, which was reported about 2 p.m. Friday, is 10 percent contained, the Los Angeles County Fire Department said Saturday.
The fire has largely burned in areas without many homes, but winds were expected to shift Saturday afternoon from the northwest to the southwest, which could drive the blaze closer to the Sand Canyon neighborhood in Santa Clarita, John Tripp, a Los Angeles County Fire Department deputy chief, warned at a noon news conference.
"Those residents have to be watching the weather, watching the media, and have to be ready to evacuate," Tripp said.
The fire's rapid growth has been fueled by "excessive heat, low humidity, extreme dry fuels that have not burned for several decades, and very rugged terrain," said Los Angeles County Supervisor Michael Antonovich, who represents the area and attended the news conference.
Fanned by gusts of up to 40 mph, the fire burned more than 2,000 acres overnight.
Weather officials warned that Saturday would mark the peak of a regional heat wave. Forecasters say temperatures in the eastern Santa Clarita Valley area _ where the fire is raging _ are expected to reach up to 106 degrees. Red-flag warnings remain in effect for much of the region until midnight.
As of Saturday morning, the blaze was "significantly larger," said Richard Lincon, a public information officer for the Los Angeles County Fire Department.
"There's a great possibility that the fire will increase in size," he said.
The strong winds and high temperatures had driven the flames into new pockets of the mountainous area Saturday, Lincon said. Steep hillsides and deep ravines have prevented fire crews from heading into some areas to dig lines that could keep the fire from spreading further.
"Probably five years ago, based on our fire behavior, if we had a similar fire, we would have probably caught this fire at the ridge," L.A. County fire chief Daryl Osby said. "Because this is the fifth year of an ongoing drought ... this fire has increased to 11,000 acres just overnight."
Meanwhile, a cloud of smoke blanketed much of the Los Angeles region Saturday morning, prompting the South Coast Air Quality Management District to issue a smoke advisory for much of the county that will remain in effect until midnight Sunday.
People are advised to avoid vigorous outdoor activity, and children, older adults and those with respiratory or heart disease should remain indoors. Residents also are being asked to keep their windows and doors closed or seek alternative shelter.
Wildfires increase the particulate matter in the air, and the increased concentration of those particles can cause irritation to the eyes, nose and throat, said Jo Kay Ghosh, SCAQMD's health effects officer. People with asthma could experience wheezing and an increased risk of attacks. The poor air quality could also affect lung functions and people's ability to take deep breaths.
Ash is a relatively large particle, but the fine, invisible particles are most dangerous because people can breathe them into their lungs, Ghosh said. Handkerchiefs and masks are likely to stop ash, but not the finer particles, she added.
If the air quality is "making you uncomfortable, do whatever you can do to remove yourself," Ghosh said. "At the end of the day, people need to use their judgment. ... For people who are sensitive, I certainly would encourage them to be more careful."
For example, Ghosh said, she lives in the Glendale-La Crescenta area, but decided to run errands Saturday despite getting blanketed in ash. However she said she also told her children, "let's not play outside today, let's play inside."
The Los Angeles County Department of Public Health has extended a heat alert through the weekend. It will remain in place throughout Saturday for the Los Angeles basin and the San Gabriel Valley and continue through Sunday in hotter regions of the county, including Pomona and the San Fernando, Antelope and Santa Clarita valleys.
"When temperatures are high, even a few hours of exertion may cause severe dehydration, heat cramps, heat exhaustion and heat stroke," said Jeffrey Gunzenhauser, L.A. County's interim health officer. "Extreme heat such as this is not just an inconvenience, it can be dangerous and even deadly."
The fast-growing Sand fire, which originated on the eastern edge of the Santa Clarita Valley next to the 14 Freeway at Soledad Canyon Road, spread southeast into the northern flanks of the Angeles National Forest, a terrain of steep arroyos and dry chaparral.
Robbie Munroe, a meteorologist with the National Weather Service in Oxnard, said winds Saturday will be weaker than they were Friday night _ gusts of only 25 mph compared with 40 mph _ but still "gusty enough to cause problems" for firefighters.
Conditions remain very dry, with only 5 percent to 10 percent relative humidity in the area where the blaze is burning, Munroe said. The combination of low humidity, high temperatures and significant winds creates conditions that make fires more dangerous _ more likely to spread quickly and more erratic, Munroe said.
"The heat and the dry air, for this time of year, aren't that unusual," he said Saturday. "If there's anything that's unusual with this event, it's the extent of the gusty north winds. And anytime we do have red-flag warnings out, we expect critical fire conditions."
Relief is on its way, though.
Forecasters expect "pretty significant cooling for coastal and valley areas" Sunday, Munroe said _ as much as a 10-degree drop in temperatures _ as the high pressure baking the region begins to weaken. The cool-down is expected to begin Saturday evening and continue overnight, though Munroe cautioned that some inland valleys could feel just as hot because humidity there is expected to increase.
On Friday, the fire forced Metrolink to stop its trains running between the Antelope and the San Fernando valleys. The California Highway Patrol partially closed north- and southbound lanes of the freeway for about an hour, and by twilight, the plume of smoke had drifted across the Los Angeles basin into Orange County, with ash falling as far east as Pasadena.
One firefighter suffered a minor injury fighting the fire, but no civilians have been hurt, Lincon said.
Officials have set up an evacuation center at Golden Valley High School in Santa Clarita; Wayside Jack Bones Equestrian Center and Hansen Dam in Sylmar are receiving large animals, fire officials said.
