North Bay again at risk of dangerous fire weather conditions denoted by red flag warning

Another spate of dangerous fire weather conditions arrived late Monday when a red flag warning took effect for the North Bay mountains, beginning a week of prolonged dry and windy weather that could prompt another round of PG&E power shut-offs.

The National Weather Service on Monday morning upgraded a fire weather watch issued Sunday to the red flag warning, meaning there’s a greater risk of dangerous wildfires from 11 p.m. until at least 8 a.m. Wednesday. After that, the threat of fire is expected to be downgraded to watch status again, from Wednesday night until Friday morning.

Winds were forecasted to gust to their strongest levels overnight Monday and Tuesday.

The greatest risk for fire is in the Mayacamas Mountains along the eastern Sonoma Valley and all the ranges encompassing Napa County, where vegetation is at record dryness, said Drew Peterson, a weather service meteorologist. There has been no measurable rainfall up to this point in wildfire season.

Elevations from 1,500 feet to ridge tops as high as 4,000 feet, such as on Mount St. Helena, where the Glass fire has been burning for more than three weeks, could experience wind gusts up to 40 mph, Peterson said. Sustained winds will blow from 10 mph to 25 mph.

“It’s a tinderbox up there,” Peterson said. “And as we know, a fire can start up in the hills and run down it. Just because the valleys are outside (the warning area) does not mean those communities ... should not be vigilant about what’s going on.”

The expected wind gusts Monday and Tuesday nights are below the 45 mph threshold PG&E uses to implement a preemptive power cut, but much of the North Bay is under a so-called watch for the potential of shutting off power later this week, utility spokeswoman Deanna Contreras said Monday.

An extended period of offshore winds and dry weather could last a week or more.

The heightened fire weather conditions could lead to a PG&E shut-off as early as Wednesday evening in parts of the Bay Area, including the North Bay, Contreras said. Pacific Gas and Electric Co. turned off power to about 1,700 customers in Sonoma County for almost two days last week, during a prolonged red flag warning that was extended twice before expiring Saturday morning.

The Sonoma-Lake-Napa Cal Fire unit expects to have 31 engines staffed throughout the duration of the red flag warning, Cal Fire spokesman Tyree Zander said. It’s the highest staffing levels the unit has had since about July, he said.

“As resources have returned from other fires, additional engines are now available within the unit,” Zander said.

Some of those units will continue to patrol the area burned by the Glass fire, which remained at 97% containment as of Monday, Zander said. Two remaining evacuation orders on the Sonoma County side of the blaze were lifted Monday, Cal Fire said.

The public is asked to avoid activities that could spark new fires during the red flag warning, Zander said. That includes mowing dry grass during peak temperatures and improperly disposing of cigarette butts and charcoals from grills.

Also, drivers should avoid pulling over to the side of the road into uncleared patches of land, where dry vegetation can make contact with a car’s hot exhaust or muffler, or letting chains drag on the ground while pulling trailers, Zander said.

“Help us by doing the right thing and remembering that one less spark is one less fire,” Zander said.

You can reach Staff Writer Yousef Baig at 707-521-5390 or yousef.baig@pressdemocrat.com. On Twitter @YousefBaig.You can reach Staff Writer Nashelly Chavez at 707-521-5203 or nashelly.chavez@pressdemocrat.com. On Twitter @nashellytweets.