Home Fire News Thousands evacuated as Oak Fire burns nearly 12,000 acres near Yosemite

Thousands evacuated as Oak Fire burns nearly 12,000 acres near Yosemite


Annie Vainshtein

San Francisco Chronicle

Firefighters battled an “explosive” fire that broke out west of Yosemite in Mariposa County on Friday afternoon and had torched 11,900 acres as of Saturday evening. Officials said tough conditions, including high heat, low humidity and bone-dry fuels, were driving the brisk growth of the Oak Fire, ballooned in 24 hours to become the state’s largest fire this season. Extreme drought conditions, increased winds and hot temperatures fueled the growth and caused spot fires to leap ahead of the main blaze, creating “explosive fire behavior” that is “challenging firefighters,” officials said.

The fire was 0% contained as of Saturday evening, officials said. Road closures and evacuation orders covering 6,000 people were in place for a wide area east and south of the fire, but no injuries or human fatalities had been reported. Thick smoke filled the air near the blaze, reached Yosemite Valley and crept toward Lake Tahoe, but hadn’t reached the Bay Area.

The cause of the blaze was still under investigation, according to Cal Fire.

Nearly 2,700 structures were threatened and at least 10 had been destroyed already, Cal Fire said Saturday. By Saturday evening, 2,093 personnel were on the scene, a dramatic increase from only around 400 Saturday morning.

“The good news is we got a lot of resources in to fight the fire,” said Amy Masi, a spokesperson with the Sierra National Forest. “The containment is at zero percent, but because we have all these people arriving, we are going to be able to put them in the most advantageous place to fight the fire and in the coming days, will see the containment increase.”

On Saturday, Gov. Gavin Newsom proclaimed a state of emergency for Mariposa County due to the blaze and California secured a Fire Management Assistance Grant from the Federal Emergency Management Agency to get the necessary firefighting resources.

The fire grew significantly in the northern section, moving further into Sierra National Forest. On the west side of the fire, crews were able to keep the fire west of Highway 140. The south side of the fire saw minimal growth.

Just before 5 p.m., the Mariposa County Sheriff’s office issued a new advisory, warning people to be ready to leave at short notice, in the Ponderosa Basin Subdivision to the fire’s east.

The prognosis for fighting the flames Saturday and Sunday was mixed. Temperatures were expected to reach the mid-90s through the weekend and no rainfall was expected, according to the National Weather Service. Relative humidity levels were also worrisome, forecast to hit single digits at times during the weekend and to hover below 15% overall, said Felix Castro, a spokesperson for the weather service’s office in Hanford ( Kings County).

Fortunately, winds were expected to be “light and bearable,” Castro said, with speeds forecast to reach 10 mph or less through the weekend.

The fire began at around 2 p.m. Friday in a sparsely populated forest area near Midpines, a town about 10 miles north of Mariposa, 35 miles northeast of Merced and 23 miles southwest of Yosemite. The fire was spreading in all directions on Friday but officials said Saturday morning it was generally trending toward the southeast.

Within hours of its start, the blaze grew to thousands of acres. Firefighters said flames were spotting anywhere up to 2 miles ahead of the fire and torching groups of trees.

“The fire moved fast, moved hot, with very big flame lengths,” said Daniel Patterson, public information officer for the Sierra National Forest. “It’s showing some pretty aggressive behavior.”

Evacuation centers were established at the Mariposa Elementary School, located at 5044 Jones St., and at the Sierra Foothill Charter School, at 4952 School House Road in Catheys Valley. Large animals were set to be transported to the Mariposa Fair Grounds.

Fire officials are hosting a community town hall at 7 p.m. on Sunday at the Mariposa County High School gymnasium.

The extreme fire conditions even generated a pyrocumulus cloud — or a fire cloud — that could be seen as far north as Reno and as far west as Contra Costa County.

The plume reached higher than 20,000 feet into the sky.

The phenomenon occurs during large wildfires in extremely hot and dry conditions. Air is rapidly sucked into the fire and upward, triggering a vertical smoke plume of ash and soot.

The harrowing plumes could be seen on satellite and hundreds of miles away, in the Bay Area.

Firefighters said Saturday morning that there was no concern the Oak Fire could merge with the Washburn Fire, a smaller blaze that broke out July 7 in the southern part of Yosemite National Park and displaced residents of the nearby town of Wawona.

That fire had burned more than 4,856 acres and was 79% contained by Saturday evening.

Aside from Washburn, California’s usual summer fire season had been eerily quiet until now.

San Francisco Chronicle staff writer Jill Tucker contributed to this report.


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