Forecasters Expect Slow Start to U.S. Wildfire Season – GWC Mag

After a wet winter, forecasters predict a slow start to the 2024 wildfire season in much of the United States. The Great Basin and Southwest may see elevated activity starting this summer. However, a likely midsummer shift in the El Niño–Southern Oscillation (ENSO), a global climate pattern marked by changes in Pacific Ocean temperatures, adds significant uncertainty to the forecast.

That outlook is a 4-month forecast produced monthly by the National Interagency Fire Center (NIFC), a group of wildland fire experts from eight federal agencies that supports and coordinates wildland fire resources across the country. The report focuses on the occurrence of significant fires—usually, those that require an NIFC management team to be dispatched—compared to the average number of such fires per year since 2000. The outlook helps fire managers determine where to allocate resources.

A Damp Start

The outlook is made using long-term forecasts from NOAA’s Climate Prediction Center, current precipitation and drought conditions, and an assessment of the types and moisture conditions of fuels (such as grasses, brush, and timber) available in different regions.

Wildfire season typically peaks in late winter and early spring in the Great Plains, in spring in the Upper Midwest and Southeast, and in summer and fall in California and the West. The April NIFC outlook forecasts out to July and thus covers much of the spring and summer fire seasons.

The most recent outlook is the “best-case scenario for California’s wildfire season.”

Across much of the United States this year, the fuels that would typically start wildfires are wet and, in some places, under snow.

In California, for example, an above-average snowpack and early spring storms will keep the state below average fire potential through July. It’s the “best-case scenario for California’s wildfire season,” said Craig Clements, a wildfire meteorologist at San José State University.

The Southwest will also have a slower start to the season after recent rainstorms soaked vegetation. 

After a mostly snow free and warm winter, the Upper Midwest is experiencing above-normal fire risk in April, making the area one of high concern to NIFC staff this spring, said Jim Wallmann, a meteorologist at NIFC and an author of the outlook. This year, Minnesota fire managers have already responded to 165 fires, and 342 wildfires have burned in Wisconsin. Wetter weather in April and May will likely decrease fire risk in the region, according to the outlook.

Midsummer Risks

The outlook is slightly more pessimistic for the summer, Wallmann said, especially for the Southwest and the Great Basin. He expects wetter fuels to dry out quickly in those regions, leading to an above-average risk of significant fires in southeast Arizona, southern New Mexico, southern Idaho, northeast Nevada, and northwest Utah starting in late May and continuing through July.

That’s similar to last year, when parts of the Great Basin had some of the highest fire risk in the country in July and August. The Hayden and Elkhorn fires in Idaho, for example, burned about 50,000 acres (20,234 hectares), and a fire in Utah’s Fishlake National Forest burned more than 7,000 acres (2,833 hectares).

Forecasters also predict an above-average potential for significant fires in Hawaii starting in May because of drought conditions. Last year, comparable conditions, combined with high winds, contributed to the devastating fire in Lahaina on the island of Maui.

The rest of the country will likely see average fire potential from mid-May through July, except for parts of California, which will still have below-average fire potential after the wet winter.

One drawback of a wetter start to the wildfire season is that fire managers have been limited in their ability to carry out prescribed burns, particularly in the Southeast, California, and higher elevations in the Southwest, said Steve Larrabee, a fire analyst at NIFC and an author of the outlook.

Prescribed burns consume wildfire fuels in a controlled manner, but wet fuel does not catch easily. Burn opportunities have been limited to burning piles of brush, branches, and trees rather than burning over large areas, he said.

Without prescribed burns, the risk of significant fires can increase, though disruptions to fuel management programs over just 1 year don’t typically escalate fire risk noticeably, Larrabee said.

La Niña Uncertainty

The further out the forecast is, the more uncertainty there is: Any singular weather event this spring, such as a strong heat wave, intense lightning, or a widespread wind storm, could quickly escalate fire activity nationally. A few days of wet weather, on the other hand, can completely reset a region to springlike fire conditions, Larrabee said. Some of those events, he said, can be “pretty difficult to predict.”

One large source of uncertainty is ENSO: Scientists expect the current El Niño pattern to weaken and transition to a La Niña pattern by midsummer. Global weather patterns such as El Niño and La Niña heavily affect wildfire season in the United States, he said.

“We’re just going to have to see exactly how this plays out.”

Midsummer rapid transitions to La Niña in past years have led to a cooler, wetter summer in many parts of the country. NIFC staff anticipate that a similar change will happen this summer, potentially lowering fire potential. But “every transition is different,” Wallmann said.

For example, a rapid transition to La Niña could also create dry summer conditions in Southern California, the Southwest, and the Great Plains, according to the outlook. La Niña could also cause a later start to typical fall precipitation in California, which could allow summer fires to persist longer than usual, Clements said. But, he said, it’s still too early to make confident predictions for late summer and fall.

“We’re just going to have to see exactly how this plays out,” Wallmann said.

—Grace van Deelen (@GVD__), Staff Writer

Citation: van Deelen, G. (2024), Forecasters expect slow start to U.S. wildfire season, Eos, 105, https://doi.org/10.1029/2024EO240165. Published on 11 April 2024.

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