Yosemite fire: Winds will be biggest challenge for firefighters

Winds will be the biggest challenge in the coming days for firefighters battling the rapidly growing Rim fire burning in and around Yosemite National Park.

The blaze, the largest wild fire burning in California, has scorched more than 133,000 acres over the past eight days and is 7% contained.

Ridge winds are expected to increase this afternoon and tonight, which could hamper containment efforts, said Kevin Durfee, a National Weather Service meteorologist in Hanford.

“It really looks like the weather is not going to be terribly cooperative in the next three days,” he said.

Winds could gust up to 30 mph in the area around the fire, and will remain strong Sunday and Monday, said Drew Peterson, a National Weather Service meteorologist in Sacramento.

Temperatures are expected to remain steady at normal to below normal, which means no excessive heat to dry out fuels, he said. Humidity will be about 20% to 25%, he said.

“It could be drier, much drier than it is. The main thing they’re going against is the winds,” Peterson said. “If they can make it until Tuesday, it looks like conditions will be better.”

Winds are expected to continue blowing from the south and southwest, so smoke should not be a problem where the bulk of Yosemite tourists are, Durfee said.

PHOTOS: Rim fire at Yosemite

More than 2,800 firefighters were battling the blaze, which was expected to grow due to “extremely dry fuels and inaccessible terrain,” according to an update from the U.S. Forest Service.

Firefighters are working to hold the fire east of the North Fork of the Tuolumne River, and crews have strengthened lines that are holding above the community of Pine Mountain Lake, the Forest Service said.

Crews are directly attacking some areas of the fire and will continue to do so as firefighters gain safe access. In areas with extremely rugged, inaccessible terrain, firefighters are creating control lines away from the active edge of the blaze. Air resources are also being used to slow the fire’s progress, the Forest Service said.

Aside from the rugged and hard-to-reach terrain, another difficulty is the blaze’s tendency to burn the tops of trees, creating a “crown fire” with long, intense flames that skip across forested land faster than a wildfire that creeps along near the ground.

Yosemite National Park remains open and is relatively smoke-free, according to the park website. The entrance from Highway 120 on the west side of the park, the Hodgdon Meadow campground and the Hetch Hetchy backpackers’ campground remained closed as of Sunday morning. All other campgrounds are open.

Popular areas in the park such as Yosemite Valley, Glacier Point, Wawona, Mariposa Grove, Crane Flat, White Wolf and Tuolumne Meadows were open Sunday.

The Black Oaks Casino Resort in Tuolumne County was advising visitors to stay away, according to its website.

The Rim fire threatened San Francisco’s power supply, damaging the Hetch Hetchy reservoir’s water and power system. The San Francisco Public Utilities Commission has been forced to shut down two of its three hydroelectric power stations near Hetch Hetchy, and Gov. Jerry Brown on Friday extended a state of emergency to include San Francisco because the reservoir is a major source of electricity and water for the city.

Firefighters were able to contain part of the fire near the reservoir and power plants Saturday, giving utility crews access to the stations to assess the damage, said Michael Carlin, a deputy general manager with the commission. The commission has purchased power on the open market and has seen only a slight dip in production as a result of the fire, Carlin said.

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Twitter: @Sam_Schaefer

Samantha.Schaefer@latimes.com