‘Extreme wildfire threat’ forecast for Northern California this summer
Historically dry conditions and temperatures predicted to be above normal this summer mean Northern California residents once again face the threat of extreme wildfires like those that have occurred with increasing regularity over the past several years, according to AccuWeather, a leading U.S. meteorological service.
The ominous forecast, though not surprising, brings into sharper view what historic drought and climate change have clarified for residents in recent weeks: catastrophic wildfires amid extremes in weather — already a regular part of life now for denizens of the American West — are likely to return in the coming months, and likely earlier in the season and extend over a longer period of time than usual.
The danger is exacerbated this year by two successive years of rainfall so low in Northern California their combined total is barely commensurate with a normal year, leaving forests and brush tinder dry, said David Samuhel, senior meteorologist for AccuWeather.
“The forests are drying. They’re turning more brown. There was hardly any new growth over the course of the rainy season, just because it was extremely dry,” Samuhel said, citing findings by the Wildfire Interdisciplinary Research Center at San Jose State University. “That’s one thing we’re really concerned about is just how dry the forests are.”
In addition, inland temperatures are expected to be several degrees above normal for much of the summer across much of the west, contributing to extreme fire behavior, he said.
Already, fuel conditions are what they normally would be in late June or early July, said Cal Fire Division Chief Ben Nicholls, who heads up state firefighting efforts in Sonoma County.
“What we’ve learned is that we’re one wind event away from a catastrophic fire, so every year has the potential to be a devastating year. But as we come into fire season 2021, we’re near or above record conditions for our energy release component,” Nicholls said, referring to a composite index that reflects the moisture content of live and dead fuels and their potential fire intensity. “We shouldn’t have the conditions we’re having until later in the summer, so the conditions we’re having now just prolong the threat.”
Those assessments join the steadily worsening outlook that has taken shape in the past few weeks, since March rains failed to put any significant dent in the now two-year rain deficit.
The state now stands at the brink of its long arid season, with reservoirs at historic lows for this time of year, low snow pack levels and moisture levels so low it has stunted spring growth in brush and trees. Seasonal fuel moisture levels in plants have been on a downward slide now for the last five years.
“That means those plants are going to be more flammable in the fall,” said Craig Clements, director of the San Jose State Wildfire Interdisciplinary Research Center.
There key “wild cards” that will dictate how bad a season it could be, particularly the degree and number of wind events and the presence of lightning, Samuhel said.
Last year’s wildfire season was the worst in California on record, with more than 4.2 million acres burned, more than 10,000 structures damaged or destroyed, and at least 31 fatalities. It was largely set off by an August lightning siege that ignited hundreds of fires around Northern and Central California in the wake of a multi-day, triple-digit heatwave, followed by period of high winds.
Those infernos included the 363,220-acre LNU Lightning Complex that burned across large portions of the North Bay, including Sonoma and Napa counties, and the million-acre-plus August Complex in Mendocino, Lake and three other counties — the largest wildfire in California history
The last time that kind of dry lightning storm hit was in June 2008, when the fuels were moister and the fires did less damage, Clements said. Those fires still burned 1.2 million acres in California, including nearly 55,000 acres in Mendocino County.
“If we miss out on lightning events (this year) “that’s going to be key,” Samuhel said.
He nonetheless forecast 9.5 million acres of land would burn across the western United States, about 140% of the 10-year average, with “above average wildfire activity” across California, but especially in Northern and Central California.
“High risk areas like Northern California are likely to take the brunt of these effects,” he said.
Nicholls said that a statewide surge that allowed 1,399 seasonal firefighters to come on duty a few weeks earlier than usual put four additional engines on standby in Sonoma County as of April 26.