Firefighters brace for unpredictable conditions at Glass Fire

As a red flag warning in the North Bay mountains got underway Thursday afternoon -- promising dangerously high temperatures, low humidity and higher winds -- officials managing the fight against the Glass Fire in Napa and Sonoma counties said they are bracing for what is predictable: uncertainty.

"It's unpredictable with what type of wind patterns," said Cal Fire Incident Commander Billy See. "There's an old saying, 'Where the wind blows that's where the fire's going to go,' and that's pretty much how we're going to watch this for right now, and plan for, and be aggressive with our tactical decisions on the ground."

The red flag warning is set to last to 6 a.m. Saturday.

On Thursday afternoon, the fire "was impinging on" Calistoga, said Cal Fire Operations Chief Mark Brunton, and firefighters were preparing defenses against points where the blaze might advance toward the city from.

"It's not into city limits by any stretch at this point, but it is something we are closely watching, monitoring and taking action on," Brunton said.

He said the fire was also "impinging on Angwin," the hilltop community southeast of Calistoga.

The fire was also pushing toward Oakville, a hamlet south of St. Helena and south of the Robert Mondavi winery, Brunton said.

In Sonoma County, Brunton said, he had a "50/50 confidence that lines cut above Kenwood and Glen Ellen would hold but there is a "potential threat" to those communities, which are roughly half between Santa Rosa and the town of Sonoma. 

Brunton said that further northwest, Kenwood, a 5,000-resident retirement community, and Santa Rosa -- which were most seriously threatened Sunday night -- "are looking very favorable and good."

In Santa Rosa, 12,925 residents remain under evacuation orders, while another 22,631 are in an evacuation warning zone, Santa Rosa Police Chief Ray Navarro said. Current evacuation figures for unincorporated areas of Sonoma County, and for Napa County, were not immediately available.

The Glass Fire had burned 56,781 acres as of Thursday morning. The fire has destroyed at least 36 single-family homes in Sonoma County, along the eastern edge of Santa Rosa, and 107 homes in Napa County, according to Cal Fire. Officials said those numbers were likely to grow.