Autumn arrives on North Coast with hot, dry weather in store, low reservoirs

Sun-baked mud is cracking along the bare margins of Lake Mendocino, the reservoir near Ukiah that helps sustain river flows for imperiled fish and supply water to 600,000 people in Sonoma and Marin counties.

The shoreline is about 100 yards out, leaving the boat ramp near Coyote Valley Dam high and dry. No people were in or on the water Monday, and geese were feasting on whatever the lake bed gave up.

As autumn begins Tuesday, the reservoir, a longtime destination for campers, boaters, swimmers and anglers, has receded considerably from its nearly 2,000-acre expanse as an overheated, arid, fiery and smoky summer gives way to another season of the very same torments.

A heat wave is in store for the weekend, along with north winds that could reload the air with harmful smoke from wildfires, some likely to continue burning until rain puts them out. And no significant precipitation is expected through the end of October.

Add to the list of woes the fact that a sudden, heavy downpour, rather than answering prayers to Mother Nature, could trigger debris flows, mudslides and flash floods over hundreds of thousands of wildfire-denuded acres on the North Coast.

Sonoma County Supervisor Lynda Hopkins, whose west county district was ravaged by the Walbridge fire this month and last, lamented the autumn of 2020 in no way resembles the seasonal respite, with cool breezes and falling leaves, she enjoyed in her youth.

“I think about what fall meant to me as a child,” she said. “Hot apple cider, pumpkin patches, going back to school. These days it means red flag warnings and smoke in the skies.”

“Right now we’re sort of stuck in limbo,” Hopkins said. “It still feels like summer outside.”

On Monday more than 19,000 firefighters were on the front lines battling 27 major blazes statewide, including the giant August Complex eating through Mendocino National Forest. At about 850,000 acres, its scale nearly matches the entire expanse of Sonoma County.

Statewide, about 8,000 wildfires have consumed more than 3.6 million acres this year, and the assault by lightning fires that erupted in mid-August accounted for the loss of more than 6,400 structures and 26 lives.

“Do not let your guard down,” Daniel Berlant, Cal Fire assistant deputy director, warned Monday.

High temperatures, along with a chance of north winds in the latter half of the week, will increase the potential for “critical fire weather,” he said. September and October have delivered some of California’s worst wildfires, he noted.

Cal Fire records show six of the state’s 20 largest fires, measured by acreage, have occurred in those two months, along with 11 of the 20 most destructive and 10 of the 20 most deadly conflagrations, with the Tubbs fire of 2017 on the latter two lists for destroying 5,636 structures and causing 22 deaths.

“We’re not out of the woods yet,” Cal Fire Division Chief Ben Nicholls said Monday, noting a flare-up within the Walbridge fire containment line over the weekend and the prospect of triple-digit temperatures into next week.

A thick band of fog is set to keep the coast cool midweek, with measurable drizzle of up to 0.05 inches.

“It’s nothing that you would clearly change your plans over,” meteorologist Brayden Murdock said.

But the ensuing heat wave will bring temperatures in the mid- to upper-90s in Santa Rosa on Saturday and Sunday, combined with possibly gusty offshore winds that would create fire weather conditions, the agency said.

There is no significant precipitation in the offing, Murdock said.

Accuweather, a private weather service that does long-range forecasting, called for rain on three days in Santa Rosa in late October, totaling about two-thirds of an inch.

“It’s not much but it’s a start,” meteorologist Jake Sojda said, calling it a “pretty good rain event” for that time of year.

The North Bay’s mountains could get an inch or more of rain, he said. But again, that is weeks away.

Consistently heavy rains typically don’t start in the area until mid- to late-November, Sojda said, noting it would be ideal to have them fall intermittently.

Prolonged heavy rain brings the risk of mudslides and flooding as water “tends to flow easily” off fire-scarred lands, he said.

Sonoma Water officials are scrambling to protect the region’s water supply from that prospect as the 55,000-acre Walbridge fire burned to the edge of about 4.5 miles of shoreline at Lake Sonoma, the largest reservoir in the Russian River system and main source of drinking water for 600,000 North Bay residents.

Lake Sonoma currently holds about 75% of its targeted capacity, while Lake Mendocino, older and shallower, is at 63% of targeted capacity.

Lake Mendocino sits close to the level it was at on the same date in the drought years of 2013 and 2015.

Far larger Lake Sonoma is virtually even with its level in 2015. Both reservoirs are holding considerably more water than they had on this date in 2014, also a drought year.

Without knowing how much rain will fall this winter, the water agency “will continue to operate under a worse case scenario and ensure every drop of water is used appropriately,” said Brad Sherwood, a Sonoma Water spokesman.

Sonoma County’s wine grape harvest started about 10 days early and will end at a similar point in the second or third week of October, said Karissa Kruse, president of Sonoma County Winegrowers.

Most of the pinot noir and chardonnay grapes have been picked, along with about half of the late-ripening varietals, such as cabernet and merlot, she said.

The persistent smoke has thrown “a curveball” into the harvest, Kruse said, raising the specter of smoke taint and leaving some growers uncertain as to whether to “pick it or leave it” without knowing how the wines might turn out.

Meanwhile, two-thirds of California was classified as being in moderate to extreme drought, according to the U.S. Drought Monitor’s report last week, up from 54% the previous week.

Nearly the entire North Bay and North Coast, including all of Sonoma, Lake, Napa and Mendocino counties, was in severe drought last week, two steps below the worst rating.

And the state was by no means alone in suffering from the heat, according to the federal government’s latest monthly global climate report.

The three-month season from June through August was the Northern Hemisphere’s hottest meteorological summer on record, surpassing both 2019 and 2016 which were previously tied for hottest, the report said.

The period, which also marks the Southern Hemisphere’s winter, was Earth’s third warmest in the 141-year record at 1.66 degrees Fahrenheit above the 20th-century average, said the report from National Centers for Environmental Information.

You can reach Staff Writer Guy Kovner at 707-521-5457 or guy.kovner@pressdemocrat.com. On Twitter @guykovner.