‘Snow-Eater’ Heat Wave Behind Big Sierra Melt Is a Look at Our Climate Future

The snowpack is melting so fast across the Sierra Nevada that ski resorts in the Tahoe area are farming snow to deepen the slush.

Meanwhile, state officials are worried the melting snowpack could lead to troubling drought and early wildfire conditions. Climate experts said the truncated winter and an early spring heat wave are exactly what they’ve predicted in a warming world. California has been baked all week with temperatures 20 to 30 degrees above normal for this time of year.

“The monthly record has already been completely smashed for South Lake Tahoe,” said Christopher Johnston, a meteorologist with the National Weather Service’s Reno office. The town set a new March record of 76 degrees on Wednesday, 5 degrees warmer than the previous record set in 2015.

Online, skiers and snowboarders have bemoaned their less-than-ideal trips down the Tahoe slopes. “It was like skiing on a slushee,” wrote one commenter on Reddit. “I’m putting a wrap on it for the season,” complained another. A third wrote what meteorologists have alluded to this week: “It’s summer already, bring your mountain bike.”

The lack of snow has caused ski resorts, including Palisades Tahoe, to close runs. Patrick Lacey, the resort’s public relations manager, said that it plans to keep operating through April and that 67% of its terrain remains open.

“Mid-morning is the best time to ski, and by afternoon it’s slushy,” he said.

Johnston said temperatures will cool by 5 to 10 degrees this weekend, but the ridge could rebuild early next week, bringing back the heat.

“We might flirt with record highs again next week,” Johnston said.

That’s bad news for California’s snowpack, which sits at 35% of the April 1 average and is quickly declining by more than a percentage point each day. Although that melt rate is cause for hand-wringing, state climatologist Michael Anderson said California’s reservoirs, where summer drinking and irrigation water is banked in manmade lakes, are generally in good condition.

Given the dismal snowpack numbers, it might seem surprising that California recorded above-average precipitation this winter, but warm winter temperatures meant that much of it fell as rain, even in the mountains.

Anderson said the season is “playing out pretty much as we expect in a warmer world.” He means human-caused climate change has altered the atmosphere enough that it’s bringing about fewer but “more punctuated” warm storms that don’t add to the snowpack and, in some cases, melt it prematurely.

“This year fits that bill,” Anderson said.

On the flip side, the heat wave is acting like a giant hair dryer blowing across the Sierra, rapidly melting snow. The northern part of the range is at 18% of the April 1 average, the central part is at 40%, and the southern part is at 57% of normal for this time of year.

Andrew Schwartz, director of the UC Berkeley Central Sierra Snow Lab, said melt rates are faster at his station northwest of Lake Tahoe.

“We’ve been losing about 8% to 13% of our snowpack per day, and that’s without the highest temperatures of this heat dome,” Schwartz said.

Schwartz characterizes this winter as ridiculously warm and said the Sierra Nevada is in the middle of “a warm snow drought.” The range saw two bigger storms this year, boosting the snowpack, but the several feet of snow that accumulated melted prematurely with rain and warmth.

“This year represents what climate change will be showing us in the decades to come,” Schwartz said. Over the next couple of decades, he expects an accelerated shift toward warmer rain-driven seasons that could peak in the 2050s, before “becoming more rain-dominated here in the High Sierra and the Central Sierra.”

Benjamin Hatchett, an earth system scientist at Colorado State University, has a term for these early-season stretches with hot days and warm nights: “snow-eater heat waves.”

He studies how they can initially lead to flooding and, later in the summer, result in problems with irrigation availability. These types of heat waves usually last up to five days and can double the melting rates.

“This heat wave is a textbook example of a snow-eater heat wave,” Hatchett said.

As human activities drive climate change, such heat waves are growing in scale and occurring earlier in the season, he found. “Without a long-term warming trend, these events were previously either unlikely or statistically impossible. We kind of unlock that possibility,” he said.

When the heat wave is over, and climate scientists study it, he’s almost certain they will find that anthropogenic warming played a big role in the warm-up.

“It’s an iconic event,” Hatchett said. “It’s something that we should expect, and when snow-eater heat waves happen, they’re going to be worse, and that increases the probability of all of these different negative outcomes.”

This year, the rapid snowmelt also means an increase in fire risk, as the forests have an extra month and a half of drying time across the range, Schwartz said.

“I think most of us anticipate kind of a rough fire year,” Schwartz said. “We’re going to have drier fuels for fires as we go into the summer.”

Schwartz also expects California’s drought map to light up in yellow, orange and red — representing dry soil, brush and trees — as spring turns into summer.

“Even if it’s a little bit of creep on that drought index map, it’s going to happen,” Schwartz said.

While reservoir levels are above average for this time of year, water experts such as Newsha Ajami, the founding director of the Risk Resilience Recovery Program at Stanford’s Doerr School of Sustainability, are considering alternative ways to capitalize on early runoff.

“Can we store some of the water we’ve released from the reservoirs that might not be needed right now in different formats, like groundwater basins?” Ajami said. “So then later, if the reservoir levels go down, we can tap into that water source.”

When Ajami considers this early-season heat wave and rapid snowmelt alongside the past 10 winters, which ranged from super wet to very dry, it shows that California cannot rely on an abundance of water.

“We don’t know what’s going to happen next year, and we need to manage the system better, as individuals and as communities,” Ajami said. “We actually do need to go back to the drawing board and think about all these pieces.”