Comment on this story
comment
Wildfire season in the West is about to kick into high gear following a scorching and prolonged heat wave in the Pacific Northwest.
Forecasters are warning of a wildfire weather pattern starting this weekend that could bring heavy lightning and erratic winds to parts of California, Oregon and the Northern Rockies.
“There’s certainly concern any time there’s a heat wave followed by lightning, especially in the middle of summer in the western United States,” said Nick Nauslar, a fire meteorologist at the National Fire Agency Interagency . “We think we’ll also see ignitions and potentially a number of significant fires.”
In an ominous sign of conditions on the ground, a new wildfire, the McKinney Fire, is spreading rapidly near the California-Oregon border after an early bout of thunderstorms on Friday. It grew explosively Friday night and Saturday with extreme fire behavior, forming a high pyrocumulonimbus cloud or fire-generated thunderstorm. The radar detected lightning triggered by the storm.
Incredibly, the fire had already grown to 30,000 to 40,000 acres by Saturday afternoon, according to the Klamath National Forest.
Mandatory evacuation orders have been issued for a wide area around the fire, and two smaller fires are also burning nearby.
There is concern that the fire could continue to spread rapidly amid hot, dry conditions near an area with no recent fire history, meaning there is a large amount of fuel (dry and dead vegetation) that it could turn on.
The #McKinneyFire in far northern California is exhibiting exceptionally extreme and erratic fire behavior tonight, producing a nearly 50,000 foot (!!) pyrocumulonimbus plume as it rapidly spreads.
This is the upper echelon of extreme fire behavior at night. #CAwx #CAfire pic.twitter.com/kAdPQ8fsbA
— US StormWatch (@US_Stormwatch) July 30, 2022
The National Weather Service in Medford, Ore., issued a red flag warning for high fire danger for the area on Saturday, and on Saturday evening extended the warning until Sunday afternoon.
“Lightning and high fire danger will likely lead to new fires. Strong winds from storms could contribute to fire spread,” he wrote. “Despite the rain, initial attack resources could be overwhelmed and residual fires are possible.”
The region has been roasting for the past week under a heat dome, a ridge of high pressure in the upper atmosphere. The dome is forecast to weaken and move eastward over the weekend and into next week, allowing for a brief intrusion of moisture from the Southwest Monsoon. Meanwhile, an approaching trough, or a dip in the jet stream, will bring cooler winds and temperatures, and act as a trigger for more organized storms.
Under this configuration, storms can move so quickly that they will drop very little rain in a given location, increasing the chances of lightning igniting vegetation in the parched landscape.
“It’s a classic critical 1-2 fire with a preceding intense and prolonged heat wave followed by ridge break,” said Brent Wachter, a fire meteorologist at the Northern California Geographic Coordinating Center in Redding, Calif., in an email. “Breakdowns in a particularly impactful heat wave event often lead to large fires due to multiple lightning ignitions … with strong gusty wind gusts and/or an increasing straight-line wind.”
While California’s fire season so far has not been as extreme as the previous two years, that could change quickly, as happened after the August 2020 lightning strike in Northern California. That year resulted in a modern record of 4.3 million acres burned in the state.
Looking at a long-term severe or extreme drought, rising temperatures this week have left a swath of the West poised to burn, as shown in a map of the energy release component, a metric that indicates the flammability of the vegetation.
“Generally speaking, sites that experience ERC values above their local 95th percentile are increasingly likely to have an ignition that escapes initial firefighting efforts and becomes a large fire,” he said. John Abatzoglou, a climatologist at the University of California at Merced, said in an email. “Notably, this becomes an even greater problem when a large geographic area simultaneously experiences high fire potential and/or there are numerous large active fires that deplete existing firefighting resources.”
According to Abatzoglou, heat waves can increase the fire season, especially heat waves that are long in duration.
Heat has been building inland in California for the past few weeks and has likely contributed to the spread of the Oak Fire outside of Yosemite National Park. That fire grew explosively without much wind in the midst of dense, dry vegetation. The fire has destroyed 109 individual residential structures as of Saturday and is 52 percent contained.
“While June was a somewhat quiet month and we largely avoided the lingering heat, things have changed over the past 3 weeks,” Abatzoglou wrote, noting that Fresno, Calif., could experience its second longest streak of days over 100 degrees Fahrenheit. for next week
Today will be the 19th straight day of triple digit heat in Fresno and Bakersfield. That triple-digit heat streak will likely end early next week. #CAwx pic.twitter.com/uPpc7BlcPO
— NWS Hanford (@NWSHanford) July 29, 2022
Record highs for July 29 were set Friday across inland portions of Northern California and the Pacific Northwest, with temperatures ranging from 100 to 115 degrees. Some places have approached record highs, or the highest temperature on record for a month. Mount Shasta, Calif., soared to 106 degrees, just one degree off its all-time high, and Medford reached 114, also one degree off its all-time high.
A study recently published in the Journal of Climate, of which Abatzoglou is a co-author, found that large fires in North America are seven times more likely to start during persistent summer heat waves. Numerous studies have linked increasingly frequent and intense heat waves, as well as increased wildfire activity and burned area, to human-caused climate change.
Even with a cooling forecast next week, fire danger is expected to remain high in the state through August, and strong fall “offshore” winds could arrive as early as September.
“This will mean that the door will be open for ignitions to become problem fires,” Abatzoglou wrote. “Widespread dry lightning … as well as wind events are certainly things to watch out for as they have the potential to dramatically alter the course of the 2022 fire season should they materialize.”
Jason Samenow contributed to this report.