California ‘weather whiplash’ fuels uncertainty in coming fire season
When Jonathan O’Brien sees the rolling green hills of Southern California, the grasses lush from this winter’s heavy rains, he can’t help but feel uneasy.
“Even if it’s not this year or next year, sooner or later we absolutely will go into a drought period again, and all this vegetation that has grown will eventually suffer — that’s just the cycle we face,” said the National Interagency Fire Center meteorologist. “When that happens, it’s all but inevitable we will see a severe fire season or two.”
This summer, however, O’Brien and other forecasters project that portions of the state could get a break. The storms of the past couple of months have left behind a deep mountain snowpack that is expected to act as a buffer against massive wildfires like those that twice burned from one side of the Sierra Nevada to the other in 2021. At lower elevations, the outlook is uncertain. Those grassy hills could burn sooner rather than later.
“Overall, we think it’s going to be a less-active-than-normal year, led by that less active component at higher elevations,” said O’Brien, who works for the NIFC’s Predictive Services in Riverside. “But the big wild card for this season is going to be the grass fire activity at lower elevations and whether we get the winds later on toward June and July to start pushing any fires around as these grasses start to dry out.”
Any lull in the fire season would just be temporary, experts say. Climate change is supercharging California’s natural climate variability, making wet spells wetter and causing dry spells to run hotter and longer. At the same time, the prohibition of Indigenous cultural burns and the effects of industrial logging and aggressive fire suppression have made much of the state’s forests more flammable.
“We definitely do see bad fire years getting worse. And there’s some evidence to suggest we will see more of this weather whiplash in the future, where we have a very wet year followed by a very dry year and we see these extreme swings from one to the other,” said Kristina Dahl, principal climate scientist at the Union of Concerned Scientists. “So it’s important to remember that those wet years don’t necessarily inoculate us from wildfires.”
This year’s exceptionally wet and snowy winter is expected to influence wildfires in several ways.
Higher elevations, especially areas above 7,000 to 8,000 feet, will remain covered in snow until much later than normal, which is expected to decrease fire activity by keeping the soils moist and vegetation green, O’Brien said.
But this year’s heavy snow and wind also brought down trees and branches, which could add to the flammability of forests under the right weather conditions, said fire meteorologist Brent Wachter with Predictive Services Northern California Operations.
“What the snow crush and the blow-downs have done is rearrange the fuel bed to make it easier for fire to transfer from the surface to canopy fuels,” he said. “And we’re still sizing that up, still figuring out how much is happening out there. Some of it is still under snow, so we don’t fully know the extent of this rearrangement.”
All that precipitation has also fueled new plant growth, or “green-up.” In lower elevations, these grasses and small shrubs and plants will cure out, or die, by the heart of the dry summer season, when temperatures are persistently hotter. That’s when they can become fuel for a wildfire.
This curing is expected to take place later than usual this year because the moisture levels in the plants are above normal, so they will take longer to dry out, O’Brien said.
In Northern California, forecasters are calling for below-normal significant large fire potential in the Sacramento Valley foothills and lower elevations of the Bay Area until June, and in most other areas until August.