Saturday Update: Dense smoke advisory extended

A respite in the smoke on Friday evening continued through the night before it started to climb again this morning.

A light west wind pushed the smoke back, so that by 7 p.m. it back down to an air quality index of 40, the lowest it has been since smoke first started pouring into the Valley on the afternoon of Aug. 22. It continued in the good to moderate range through the night, until this morning at about 6 a.m., when the monitor located at Ranchos Aspen Park showed the index climbed to 110, unhealthy for some groups.

The National Weather Service extended a dense smoke advisory through 8 p.m. tonight. Visibility is expected to drop down to a mile at times, though there may be some clearing later this morning into early afternoon.

The smoke is coming from the Rim fire burning west of Yosemite, which was up to 219,277 acres this morning, up from 201,894 acres on Friday morning.

A change in the wind direction that cleared most smoke from Carson Valley last night drove it into Yosemite Valley where web cams show the pall cast over the park.

Active burning prompted the expansion of a mandatory evacuation in Mariposa County.

Nearly 5,000 firefighters are working to bring the giant blaze to heel, but torching and crowning in the heavy timber are combining with winds to drive it north, east and south into the Sierra’s rugged terrain.

Nearly a dozen homes have burned in the fire, which has claimed 111 structures, mostly outbuildings. The California Department of Forestry reports 5,000 structures are threatened, including 4,500 homes. Mandatory evacuations were expanded on Friday night as the fire spotted across Old Yosemite Road. Highway 120 at the Yosemite National Park boundary west to Buck Meadows has been evacuated.

Firefighters have a line around 35 percent of the fire, but it continues to grow southeast into Yosemite National Park and northwest. Full containment of the fire isn’t expected until Sept. 20, but portions could continue to smolder until the rainy season arrives.