Authorities in California are bracing themselves for a prolongued heat wave this week that could amplify the risks of a wildfire and intensify fires already burning in the southern and central portions of the state.
The warming trend is forecast to bake almost all of inland California over the next week, dialing up the heat on what's already been a fiery summer in the state's southern half, and raising the risks up north after a relatively quiet start to the season.
“This week will definitely bring those elevated fire weather conditions," said Adam Roser, a meteorologist at the National Weather Service in San Diego. In Southern California, "the vegetation is still very dry. ... [and] these are definitely some of the hotter temperatures we've seen so far this summer."
Southern California's hottest days are expected to be Wednesday through Friday, when much of the interior is under heat advisories as temperatures are forecast to range from the upper 90s to the triple digits across many valleys and deserts. Palm Springs could reach up to 118 on Thursday while downtown Los Angeles could hit 90.
Weather service officials warn that there will be an increased risk for heat sickness and fires to start and grow out of control.
Read more: California is on pace for its worst wildfire year in recent memory, and SoCal is mostly to blame
Already, much of inland Southern California is under a wildfire smoke advisory from three large fires burning in the region: the Gifford fire in Santa Barbara and San Luis Obispo counties — now California's largest blaze of the year at 82,000 acres, the Rosa fire in Riverside County and the Gold fire in San Bernardino County.
Inland Northern California will see temperatures climb by this weekend, when highs are forecast to reach into the triple digits across many areas. Parts of the Sacramento Valley could reach 107, while areas of the state's northwest corner could see highs of 105 to 113. In the San Francisco Bay Area away from the coast, highs could reach into upper 90s.
Although the fire threat there remained unseasonably low for much of July, the weather service warned that vegetation has started to dry out and will continue to do so as temperatures rise.
"The warming trend we’re forecast to have will only compound our concerns," said Matt Mahle, a Bay Area meteorologist at the weather service who pointed out that the region has seen several small fires over the last week.
But luckily, strong winds aren't forecast to mix with this heat wave, which could result in a deadly wildfire recipe.
Still the scenario this week has the potential for dangerous conditions, with a easy-to-burn vegetation, high temperatures and low humidity. Officials say those conditions can help foster fires that can create their own winds.
That phenomena, known as a plume-dominated fire, has already been spotted several times by crews fighting the Gifford fire, where massive smoke plumes have shot hundreds of feet in the air, then collapsed on itself, creating localized wind gusts.
The Gifford fire, burning mostly in the Los Padres National Forest along mountains in the Central Coast, was only 7% contained as of Tuesday morning, with a major stretch of State Route 166, east of Santa Maria, still closed, according to the latest update from the U.S. Forest Service. More than 500 homes in nearby rural communities have been evacuated, officials said, while almost 900 structures remain threatened as the fire continues to grow.
Crews there have been battling the flames in 90-degree heat since last week, but are bracing for temperatures near 100 through Friday, which will only create more challenging conditions and increase fire behavior, said Santa Barbara County Fire Capt. Scott Safechuck.
And then for the firefighters, they’re exerting themselves in extreme temperatures," Safechuck said.
Crews are also still battling two smaller fires in inland Southern California, both of which ignited Monday. The Rosa fire in the Santa Rosa Mountains in Riverside County appeared to be holding at 1,2000 acres as of Tuesday morning, though evacuation orders there remained in place. In the San Bernardino County mountains, the Gold fire burned through 348 acres Monday, and remained at that size Tuesday morning, despite officials reporting challenging conditions, including short-range spot fires and rugged terrain. Neither the Rosa fire nor the Gold fire had any containment as of Tuesday morning.
Read more: Southern California on alert for severe wildfires after dry winter
These active fires only add to an exceptionally busy fire year thus far, which is looking like it could be California's worst year in recent memory. Southern and Central California have driven that active start to the year, recording several major fires already, including Los Angeles' unprecedented January firestorm. But officials say there's still a lot of time for things to change, as late summer and early fall are often the busiest time.
This week's heat wave is only expected to exacerbate those challenges.
“These are definitely some of the hotter temperatures we’ve seen so far this summer,” Roser said, the weather service meteorologist. "This might be one of the longer [heat waves] this year."
A widespread heat advisory has been issued for much of San Diego, Orange, San Bernardino and Riverside Counties from Wednesday through Friday, with highs expected in the Inland Empire up to 105. San Diego County's valleys could see temperatures peak around 102, while inland Orange County, the Santa Ana mountains and the San Bernardino mountains will reach into the 90s.
An extreme heat warning will be in effect Wednesday through Friday for the Coachella Valley, the San Gorgonio Pass near Banning, the San Diego County deserts and into California's southeastern deserts, with highs expected to reach from 106 to 118.
"An extreme heat warning means that a period of very hot temperatures, even by local standards, will occur. Actions should be taken to lessen the impact of the extreme heat," the warning said. "Anyone overcome by heat should be moved to a cool and shaded location. Heat stroke is an emergency!"
The weather service's heat risk map warns of widespread moderate risk across Southern California Thursday, with major risk across the low desert. The coast will be largely spared. Much of inland Northern California will see moderate heat risk by Saturday.
In the L.A. area, officials are expecting triple digit temperatures in the hottest valleys and high deserts on Thursday and Friday, including Santa Clarita and Lancaster, while highs are forecast to reach into the 90s in Sherman Oaks and Pasadena.
Bryan Lewis, a weather service meteorologist in Oxnard, said that Southern California could come close to reaching its hottest day this year on Thursday, when the heat wave is expected to peak in the Southland.
Temperatures should slightly fall by the weekend, but remain several degrees above average for days, possibly through next Wednesday, Lewis said.
This story originally appeared in Los Angeles Times.
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