In an ominous forecast for the fire-ravaged region, the National Weather Service issued a fire weather watch for winds gusting up to 60 mph Friday night in the North Bay hills.
Winds of that magnitude would mirror the conditions that gave rise to the firestorm that roared late Sunday over the hills from Calistoga, bringing death and widespread destruction to Sonoma County.
“It would be catastrophic,” Cal Fire Capt. Richard Cordova said. “We would have no control over the fire.”
He said marginal containment of the largest blaze, the Tubbs fire, would be wiped out, noting the other wildfires in the region have little containment. “We would be starting from square one again.”
Cordova said Cal Fire’s own forecasts call for smaller gusts: up to 40 mph in the hills Friday night.
Weather service predictions for 50 mph gusts Wednesday never materialized.
Meanwhile, smoke from the North Bay fires fouled the air Thursday throughout the San Francisco Bay area, with unhealthy air levels recorded from Concord in Contra Costa County to Redwood City in San Mateo County.
“It was a bad air day for most of the area,” said Tom Flannigan, a spokesman for the Bay Area Air Quality Management District.
The district measures small particle pollution, typically associated with wood burning, at 17 locations and 13 recorded an “unhealthy” level of pollution Thursday, well above the federal health standard.
Napa had the worst score and was alone in touching the highest level, deemed “very unhealthy.”
Vallejo, San Rafael and San Pablo also had high counts of unhealthy air.
Sebastopol, where the air district’s only Sonoma County monitor is located, was in the moderate range most of the day and even recorded a “good” level in the late afternoon.
Air district officials said Sonoma County as a whole has had the dirtiest air ever recorded by the district since the wildfires erupted Sunday night.
The fire weather watch issued Thursday covers the period from 5 p.m. Friday to 11 p.m. Saturday, with warm, dry north winds of 25 to 35 mph in the hills Friday, growing stronger during the night with gusts approaching 60 mph, meteorologist Rick Canepa said.
The combination of wind, low humidity and bone-dry wildland fuel adds up to “critical fire weather conditions,” he said. “It’s extremely dangerous.”
Winds are expected to abate by Saturday afternoon to the 15 to 30 mph range in the North Bay hills and mountains, Canepa said.
Sunday, winds are forecast to be lighter still, he said.
Rain would be welcome, and there’s a possibility of light rain in the North Bay and around the Bay Area late next week, Canepa said.
Up to three-quarters of an inch of rain could fall Thursday and Friday, he said, acknowledging that more would be better.
“We need some good soaking rains” to quell the region’s fire risk, Canepa said.
You can reach Staff Writer Guy Kovner at 707-521-5457 or firstname.lastname@example.org. On Twitter @guykovner.