An extreme heat event and strong winds are sending fire danger soaring yet again across nearly the entire state of California, from the north to the Mexican border. Any fires that start Friday could spread rapidly out of control, particularly in the San Francisco Bay area and Southern California.

The state is still dealing with the effects of its worst wildfire season on record, with more than 4.1 million acres burned, more than twice the previous record set in 2018. It’s also grappling with the dilemma of how best to carry out preemptive power cuts in fire-prone areas, which has proved to be an effective way of reducing ignitions.

Short- to medium-term forecasts are foreboding, as computer models signal the possibility of similar fire weather outbreaks in the next two weeks.

One additional strong wind event may occur in Northern California midweek next week, for example, although the intensity of that episode is currently unclear.

Red flag warnings are in effect Friday through late morning local time in Northern California, where strong land to sea winds, known as El Diablo winds, plus dry air are causing fire danger to spike. In the Bay Area, though, red flag warnings will continue through 6 p.m. local time, including in the North Bay valleys and mountains, East Bay valleys and mountains, as well as the Santa Cruz mountains.

This region includes some areas hit hard in the past two months by swift and deadly wildfires, some of which traveled 25 miles in one day.

Many of the state’s recent destructive blazes are still burning, so the high winds threaten to reverse some of the progress firefighters have made in recent weeks. In addition, any new fires that start would grow rapidly and exhibit extreme fire behavior, the National Weather Service warns.

Heat advisories are in effect Friday for the entire San Francisco Bay area all the way to the southern border with Mexico for potentially record-breaking heat. Temperatures in the Bay Area, for example, are predicted to reach the 90s on Friday, 15 to 25 degrees above average, with inland areas reaching the 100s.

Cooler and somewhat more humid air is expected to move into Northern California late this weekend into early next week, temporarily reducing wildfire risks, but wildfires will remain a major concern until winter rain and snow move in from the Pacific.

On that point, the Weather Service is not optimistic. In a technical forecast discussion, meteorologists at the agency’s San Francisco office stated early Friday: “Still no rain in sight.”

Preemptive power shut-offs

In response to this spike in fire risk, which has featured 60-to-70-mph El Diablo winds blowing dry air across the Sierras, and slightly lesser winds clocked in the North and East Bay along with Napa and Sonoma, Pacific Gas and Electric moved ahead with power cuts to a total of about 53,000 customers in 24 counties from Wednesday night into Thursday.

The proactive power cuts have been criticized, but some experts say that with the state facing the ravages of climate change along with decades of forest management policies that have allowed fuels to build up, they’re needed to prevent blazes.

“We have had a historic fire season this year, and it has been extremely challenging for many,” Scott Strenfel, PG&E’s lead meteorologist, said in a video update Tuesday. “We are now and continue to be in the peak of fire season until the rain and snow returns.”

Some of the deadliest wildfires in recent history have been traced to downed or faulty power equipment, including the 2018 Camp Fire in Paradise — the deadliest on record in the state, which was traced to a PG&E transmission line.

In late October 2019, PG&E cut power to nearly 1 million customers to avoid having their equipment spark wildfires during extreme winds.

“The power shut-offs last year prevented what would have been large-scale conflagrations,” said Michael Wara, director of the Climate and Energy Policy Program at Stanford University. “The system damage that was observed after these October shut-offs demonstrated that they were the right thing to do and people are alive today because the power was shut off.”

Climate change has raised the stakes of any kind of ignition, with fires moving farther and faster and burning with higher intensity as increasing temperatures dry out the landscape.

Now utilities and the public are stuck in a Catch-22: cut off electricity to prevent another catastrophic wildfire and leave large swaths of the population in the dark, potentially without access to lifesaving warnings and services during an emergency; or keep the power on and risk sparking a conflagration.

With the help of in-house meteorologists, utilities are working to narrow the scope of this year’s shut-offs, called Public Safety Power Shutoffs (PSPS). But those plans might be foiled with fire danger running much higher in 2020 than in 2019, amid another dry and possibly very windy October.

Fire weather will ultimately dictate shut-offs

With much-needed rain bypassing the state, California finds itself in the most intense part of its fire season, when dry offshore winds strengthen and become more frequent.

“It is imperative that we de-energize for safety when high fire risk conditions are present and forecasted high winds begin to materialize,” Chris Arends, meteorology program manager at San Diego Gas and Electric, said in an email.

San Diego Gas and Electric pioneered the use of power shut-offs after its equipment was found to have caused devastating fires in October 2007, and is considered a leader in its efforts to reduce electrical ignitions while trying to avoid widespread power outages.

A recent study found that last year’s broad and disruptive shut-offs imposed by PG&E were more sweeping than would have been warranted when strictly applying the company’s weather criteria for turning off power.

To reduce the footprint of power loss this year, PG&E has expanded its weather station network and is employing a new, higher resolution weather model for more precise forecasts. It has also been working to “sectionalize” the grid by adding switches so that smaller areas can be turned off.

“This is all toward the goal of reducing the impact of Public Safety Power Shutoffs and only de-energizing areas that are at highest risk,” said Scott Strenfel, PG&E’s meteorologist, in an interview.

So far, that goal has held. In addition to the 53,000 customers who lost power this week, fewer than 70,000 lost power during the fire weather in late September.

However, with drier fuels and the likelihood of a stronger wind event than has occurred so far, it’s possible a more expansive power shut-off will still take place this year.

“Yes, the shut-offs are more targeted this year,” he said. “However, that doesn’t mean we couldn’t have a bigger, stronger event than last year or drier fuel moisture.”

A long road ahead

There are ways out of the wildfire-powerline entanglement, but most are expensive, labor-intensive and have a very long time horizon. For example, utilities are working to bolster power lines against electrical failure. But PG&E’s territory contains 10,000 to 30,000 miles of lines in need of upgrade.

Wara said one priority would be to fix the state’s aging transmission system. PG&E’s old and poorly maintained transmission towers were the culprit in both the Camp Fire and the 2019 Kincade Fire, which forced mass evacuations in Sonoma County.

Unlike local distribution lines, these towers form the backbone of the electrical grid and connect different regions. De-energizing them can affect millions of customers, including those in urban areas such as San Francisco.

“Transmission lines transport a large amount of power, and if several such lines are turned off you can really start to see large-scale power shut-offs,” said Line Roald, an assistant professor of electrical and computer engineering at the University of Wisconsin at Madison.

According to Roald, impacts to communities should be a fundamental part of the equation when deciding when and where to de-energize. She and her colleagues are studying whether wildfire risk reduction can be achieved without widespread disruptions in service, which are “absolutely non-ideal and not how we want things to be,” she said.

In the meantime, power shut-offs will continue, even though rural and poorer communities such as those in the Sierra foothills are bearing the brunt of their repeated impacts.

“I think we need to be realistic about power shut-offs being part of the solution set,” Wara said.

“Fire season is not going to get better — it’s going to get worse.”