Seeing smoke in the Southern California mountains? It may be a prescribed burn

Upland, CA - U.S. Forest Service firefighters in the Angeles National Forest burn piles of forest debris below Mt. Baldy on Wednesday morning, Nov. 29, 2023. Controlled burns are part of the service's forest management practices. (Luis Sinco / Los Angeles Times)
A prescribed burn caused this charred vegetation in Angeles National Forest last year. Smoke may be visible this week if conditions are right for a prescribed burn. (Luis Sinco / Los Angeles Times)

L.A. and San Bernardino county foothill communities may soon see smoke from a controlled fire in the Angeles National Forest, officials said.

Firefighters are waiting for the right conditions to converge to ignite the Tanbark prescribed fire in the mountains above Glendora, San Dimas and La Verne, which could happen as soon as this week, the U.S. Forest Service said. The burn did not begin today, and the Forest Service said it would check conditions again Thursday.

They will intentionally apply flames to a landscape that's been carefully prepared, with brush cut back in strategic areas and piled to help manage the fire's speed and intensity, said Dana Dierkes, public affairs officer with the Forest Service.

"This effort will allow the fire to burn up to 500 acres by backing slowly downhill into part of the San Dimas Experimental Forest and into the adjacent area," Dierkes wrote in an email.

The area is surrounded by a line of bare soil, and the fire's perimeter will be staffed with firefighters who will make sure it remains within the planned boundaries until it's declared to be out, she added.

The burn is to maintain an existing system of roadside fuel breaks — strips of land where vegetation has been completely or partly removed — to help firefighters fight wildfires, Dierkes said. Another goal is to reduce the amount of burnable plant material in the area to lower the risk of wildfire spreading from the forest into nearby communities, or vice versa, she said.

Once the burn gets underway, smoke is expected to be visible inside the San Gabriel Mountains National Monument portion of the Angeles National Forest, and may linger for a few days, officials said. Smoke may also be seen in Monrovia, West Covina, Glendora, La Verne, San Dimas, Claremont, Upland, Mount Baldy, Rancho Cucamonga, Ontario, Pomona, Chino and Diamond Bar, according to the Forest Service.

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The operation comes as California has sought to step up prescribed burns in the state, with a goal of setting fire to 400,000 acres a year by 2025. Experts say that encouraging low-intensity fires that consume potential wildfire fuel when conditions are favorable can help mitigate catastrophic fires that burn out of control when the weather is hot and dry.

Other purposes of controlled burns can include killing invasive plants, helping other plants grow and controlling insect populations. Some Indigenous groups, who pioneered the idea, also burn to achieve a variety of ceremonial and cultural objectives.

Before a burn gets underway, officials must verify that specific weather and air quality conditions are in place to ensure the fire will achieve its objectives and will not spread too quickly, escape control or expose nearby communities to an unacceptable level of smoke.

Firefighters had initially hoped to start the Tanbark prescribed fire Monday, but environmental conditions were not satisfactory, the Forest Service said. Officials said they would assess conditions on a daily basis to decide when the burn can begin.

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This story originally appeared in Los Angeles Times.