Red flag warning puts fire crews on alert in Sonoma County this weekend

With a red flag warning in effect this weekend, portending another round of dangerous fire conditions, authorities have an important fact to share for North Bay residents bracing for hot, dry and windy weather: More than 90% of wildfires are caused by people.

“We ask that everyone remains vigilant in their fire safety out there ... If the public does their part, hopefully we’ll get through this with no new fires,” said Cal Fire Division Chief Ben Nicholls, calling out the statistic.

The risks were driven home Thursday when a landscaping crew sparked a brush fire around noon near Larkfield, in the 2017 Tubbs fire scar. Helicopters, air tankers and ground crews kept the flames to 12 acres and no structures were damaged.

But fire resources are stretched thin statewide, with 25 major fires still burning and 17,400 firefighters on the front lines.

The red flag alert, issued by the National Weather Service, recognizes the critical conditions expected this weekend, including strong offshore winds, low relative humidity and warm temperatures, all of which can contribute to extreme fire behavior. The alert will be in effect from 9 p.m. Saturday to 8 a.m. Monday.

The hot, dry, windy conditions can reignite or feed hidden hot spots in fires that are otherwise under control, like the Walbridge fire in northwest Sonoma County.

Containment on the Walbridge remained this week at 98%, with no growth beyond its existing 55,209-acre footprint. Fire officials are keeping an eye on any smoking embers within the perimeter.

“We have a pickup with a pump and small water tank attached to it patrolling the fire every day,” Nicholls said. “They’re finding three to five smokes per day to extinguish.”

Winds this weekend could complicate that effort. But Nicholls said Cal Fire’s equipment and resources are ready to go and they’re working with local agencies as well.

“To try to have the best initial attack capacity on hand, we’re increasing the firefighter number on the fire engines we do have,” from three to four per engine, he said.

As of Friday, Pacific Gas & Electric has no plans to cut off electricity due to fire danger in Sonoma and Mendocino counties, the utility said.

Nearby Napa and Lake counties were added to a list late Friday of 15 counties where transmission lines could be temporarily powered down if weather conditions deemed it necessary, however.

That was up from three counties ― Butte, Plumas and Yuba― warned earlier Friday afternoon of potential power shutoffs over the weekend.

Roughly 97,000 customers could be affected by the shut-off statewide, 181 of them from Napa County and another 55 from Lake County, near Middletown, PG&E spokeswoman Deanna Contreras said.

Nicholls said overstretched fire agencies were on high alert with the latest red flag warning.

“That gives us pause,” he said. “We do have still the 25 fires that are burning across the state. Ultimately, we don’t have the resources we’d have normally.”

Statewide, 1,900 fire engines are committed to those fires, unavailable for other work.

“That means locally for us, we have open (unstaffed) fire stations. In Sonoma County one of the nine fire stations is open because of the drawdown across the state,” Nicholls said.

The area under biggest threat from weather-fire danger will be the hills of northeast Sonoma County and Napa County above 1,000 feet, with the strongest winds near Mount St. Helena and also at Mount Tamalpais in Marin County.

Any fires that develop could spread rapidly.

Offshore winds from the north and northeast should gust as high as 35 to 50 mph Saturday night, said weather service meteorologist Roger Gass.

Those winds will be whipping amid above-average temperatures in the upper 80s to mid-90s on Saturday, increasing to the mid-90s up to 103 in the hottest areas of Sonoma County on Sunday and Monday, he said.

Winds will ease during the daylight hours, but another burst of offshore winds will develop Sunday night into Monday morning.

Humidity is anticipated to range from 30% to 45% Saturday evening but will drop overnight as offshore winds develop, hitting 10% to 25% Sunday into early Monday, with no humidity recovery Sunday night, the weather service said.

By Sunday night, the persistent drying offshore winds will reach the Sonoma Coast, including the Walbridge fire area.

A strike team that will add backup is coming in from Pine Grove Camp, adding another 24 to 30 personnel. That team will be positioned in the Fairfield area for any new fires in the Sonoma-Lake-Napa Cal Fire unit.

“The good news is, we have all of our normal, day-to-day initial attack ready,” Nicholls said.

That includes two air tankers, a helicopter and six bulldozers.

“And we have had conversations with the August Complex (in Mendocino County),” he said “and the resources we currently have working on Walbridge to make resources available for any new starts.”

Staff Writer Nashelly Chavez contributed to this story. You can reach Staff Writer Lori A. Carter at 707-521-5470 or lori.carter@pressdemocrat.com. On Twitter @loriacarter.