A firefighter monitors the Kincade Fire as it burns through the area on Thursday in Geyserville, Calif. (Justin Sullivan/Getty Images)

Rapidly spreading wildfires have erupted amid “extremely critical” fire danger in parts of California, with conditions likely to escalate risks to Southern California, including the Los Angeles area, through Friday.

In Northern California, the Kincade Fire in Sonoma County, about 75 miles north of San Francisco, rapidly expanded in size early Thursday morning, torching 10,000 acres in just four hours. A red-flag warning is in effect for much of the San Francisco Bay area through 4 p.m. Thursday, as high offshore winds of up to 60 mph in some locations, combined with extremely dry air, create ideal conditions for rapidly spreading wildfires. The offshore winds in Northern California are forecast to slacken as the day goes on, potentially giving firefighters a window to make gains on that blaze and any others that erupt during the day.

However, relative humidity is not expected to recover much overnight, which could make wildfires more difficult to contain.

Tinderbox conditions

The wildfire threat in Southern California will ramp up throughout Thursday, with the National Weather Service forecast office in Los Angeles warning of “an environment ripe for large and dangerous fire growth, especially Thursday and Friday.” Forecasters are warning of “extreme fire behavior” for any blazes that erupt through Friday.

The NWS is predicting “isolated gusts to 75 mph below passes and canyons” with relative humidities “around 5 percent” in parts of Ventura and Los Angeles counties through Friday.

“This has all the ingredients of a dangerous fire weather scenario,” wrote the office, calling it “similar to or worse than the recent Oct. 10-11 event that produced the Saddleridge Fire.” They urged extreme caution, mentioning that actions as simple as “dragging towing chains” can create the sparks that metastasize into a wildfire.

The dry air is also allowing the ground to bake and temperatures to skyrocket. Los Angeles could hit 95 degrees Thursday, encouraging the evaporation of any remaining moisture in the plants, leading to more dried-out vegetation and littering the ground with fuel to nourish the next big blaze.

Even in San Francisco, the downsloping winds will lead to unusually hot conditions, with a head advisory in effect on Thursday. Heat advisories have also been issued in southern California, where coastal residents accustomed to moderating winds off the Pacific Ocean will suffer through temperatures in the upper 80s to mid-90s.

Ominously, forecasters and firefighters are eyeing a second round of “even stronger” offshore Santa Ana winds set to plague much of California this weekend, with “pockets of critical fire weather” likely per the National Weather Service.

The Kincade Fire

The Kincade Fire, which remains at zero percent containment, started just before 9:30 p.m. in Geyserville, with the cause still under investigation, according to local officials. It has quickly swallowed surrounding areas in flames, expanding at an average rate of a football field every two seconds — or 30 football fields each minute during a four-hour period early Thursday. Winds in the vicinity of the fire gusted as high as 76 mph, propelling the flames and spreading embers far ahead of the fire front

Evacuations have been ordered in parts of Sonoma County, including the community of Geyserville.

The fire is surging south, and has crossed Highway 128. Some of the smoke could cloud Bay Area skies on Thursday afternoon, or more likely on Friday. Aviation forecasters warned that smoke could reduce the visibility for planes operating in and out of San Francisco International Airport on Friday.

The Kincade Fire comes two years after the deadly Tubbs Fire devastated nearby Santa Rosa. At least 22 people died, and more than 5,600 homes and buildings were destroyed in that blaze, which occurred in similar weather conditions.

The Old Water Fire

Meanwhile, another fire is burning in Southern California, just north of San Bernardino. The Old Water Fire, which was burning in a primarily rural area Thursday morning, has charred 50 to 100 acres — but the San Bernardino County Fire District warns of the “potential for [large] growth as Santa Ana winds pick up.”

An “even worse” round this weekend

A surge of extremely dry air and offshore winds will overspread much of California beginning Saturday night and lasting through at least Monday. (WeatherBell.com)

Following a brief improvement late Friday into Saturday, a renewed threat of high fire danger is in the cards Saturday evening through Monday. The National Weather Service is referring to this as an “even stronger wind event,” with drier air, and the risk could encompass everywhere from the forests of the Sierra Nevada Mountains to the urban sprawl of Southern California.

Wind gusts in excess of 60 mph are possible in the higher terrain and foothills throughout much of Northern and Central California, with relative humidity dropping as low as 3 percent.

Preemptive blackouts and a changing climate

Pacific Gas & Electric employees work in the PG&E Emergency Operations Center in San Francisco earlier this month. (Jeff Chiu/AP)

Meanwhile, California’s electrical providers have instituted the second round of “public safety power shutoffs” in two weeks to reduce the risk of sparking a blaze when dangerous fire weather is present. Pacific Gas & Electric cut service to more than 182,000 customers, beginning Wednesday in the Sierra foothills and North Bay and early Thursday morning in San Mateo and Kern Counties. “For planning purposes, we suggest customers prepare for multiple-day outages,” PG&E wrote on its website. Southern California Edison, the state’s other major provider of electricity to more than 14 million people, has shut off power to 15,000 so far. Another 286,000 are “under [public safety power shutoff] consideration.”

Additional shutoffs may become warranted with the second event over the weekend.

California’s preemptive power cuts are a new and extreme way of adapting to an environment that scientists say is more conducive to large wildfires and longer fire seasons. This is largely due to a combination of climate change and land use shifts.

The ongoing wildfires come on the heels of the devastating 2017 and 2018 California fire seasons, which featured the largest, most destructive, and deadliest blazes on record. The Camp Fire, for example, occurred nearly one year ago, killing 88 and destroying much of the town of Paradise. An investigation concluded that the fire began from a spark generated by a Pacific Gas & Electric power line.

It’s part of a clear pattern toward larger, more frequent and destructive blazes. And, according to CalFire, “climate change is considered a key driver of this trend.” Population growth and the increase in homes and businesses located near lands that typically burn, known as the wildland-urban interface, are also escalating the risk of and damage from wildfires in the Golden State.

“Warmer spring and summer temperatures, reduced snowpack, and earlier spring snowmelt create longer and more intense dry seasons that increase moisture stress on vegetation and make forests more susceptible to severe wildfire,” the agency wrote. “The length of fire season is estimated to have increased by 75 days across the Sierras and seems to correspond with an increase in the extent of forest fires across the state.”

Partly because of its experience with wildfires, California has established the most ambitious climate policy targets in the country, but the consequences of global warming are already here, and increasingly obvious.

One of the most robust conclusions of climate change research is that wildfires are becoming increasingly frequent and severe in large parts of the American West as the climate warms, particularly in California. This is taking place as summers become hotter and drier and precipitation becomes more variable in the winter, with jarring shifts from drought to flood and back again becoming the norm.

For example, the National Climate Assessment, an authoritative report published by the Trump administration in 2017, showed that the cumulative forest area burned by wildfires in the Southwest between 1984 and 2015 doubled because of climate-change-related factors.

In an indication that an uptick in large wildfires is occurring in California, 15 of the top 20 largest wildfires in state history have occurred since the year 2000.

Computer model projections show huge increases in wildfire frequency and size in California, as well as other parts of the Southwest, if greenhouse gas emissions continue largely unabated.

Kim Bellware contributed to this report.