Despite dire warnings, air quality in Carson Valley improved measurably hitting moderate levels during most of the day, even getting into the green category this afternoon.
The Nevada Department of Environmental Protection’s air monitor at Ranchos Aspen Park showed an air quality index of 20 at 1 p.m. down from a high of 155 at 8 a.m., which put the quality in the unhealthy range.
Residents on either side of the Valley could see the mountains on the opposite side, a vast improvement over the worst levels of smoke experienced on Aug 22 and 25.
A dense smoke advisory for Carson Valley was canceled this afternoon, but is still in effect for southern Douglas County, Alpine and Mono counties, where visibility will be less than a mile through 5 p.m. Sunday.
A shift in the wind from the predominant southwesterly direction to southeast starting about 8 p.m. Friday is responsible for pushing the smoke out of the Valley. According to the weather station at the Fish Springs Volunteer Fire Department, the wind was blowing steadily out of the west to northwest.
A shift in the wind back to the southwest could again bring smoke into the Valley.
By 7 p.m. Friday the smoke quality was 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.
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.