After Palisades Tahoe avalanche, how to stay safe on the slopes

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Nothing can draw eager crowds to the mountains like fresh powder, but in the wake of a deadly avalanche this week at Palisades Tahoe, new snow should be a sign to skiers, snowboarders and hikers to be more aware, experts said.

The avalanche Wednesday killed one skier and injured a resort guest. They were the first avalanche-related death and injury of the 2023-24 season in the U.S., according to the Colorado Avalanche Information Center. (One day later, an avalanche in the Idaho backcountry left one man dead and two injured, authorities said.)

Avalanches are rarely a danger within ski resort boundaries, where workers reduce the risk through stability testing and the use of explosives or artillery to trigger avalanches when the slopes are empty. But where there’s one avalanche, experts said, more are likely to follow, so visitors should exercise caution.

The three-day holiday weekend — and the promise of several more inches of snow from a storm on the way — is likely to draw heavy crowds to the mountains. Palisades Tahoe reopened Thursday, and the KT-22 chairlift, where this week’s avalanche occurred, was back in operation Friday.

If you plan on heading out, here are some tips. They are most relevant for backcountry trekking, but skiers should also keep them in mind.

“The thing is, this is Mother Nature,” said Tim Keating, founder of SWS Mountain Guides, a company that provides skiing guides and certified avalanche training. “Avalanches are an art, not a science.”

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Avalanche warning signs

Individually, each of these five red flags doesn’t usually mean there is avalanche danger, Keating said. But when observed in multiples, the risk has increased, and discretion is called for.

Rapid snowfall: There’s no scientific formula, but Caleb Burns, co-owner of SWS Mountain Guides, suggests that any significant snowfall in a short amount of time can be a red flag.

“If we’re looking at 10 inches in a day, 20 inches in a day — that’s a lot,” he said.

Diagram shows recently fallen snow can add extra weight on the snowpack, causing it to weaken and break off.

Signs of recent avalanches: Burns referred to avalanches as a “herd species.”

“If you see signs of an avalanche, there are probably more to come,” he said.

They may not be obvious to an untrained eye, but an old avalanche can look like “a still photo of a waterfall” or a mudslide that’s been painted white, he said.

Diagram shows signs of debris at the bottom of a slope can indicate a recent avalanche.

Strong winds: These can move and shift snow easily, Burns said, and pile up a thicker layer of weak snow in areas.

Diagram shows winds can blow snow to already overloaded snowpacks, creating unstable conditions.

“Whumpfing”: This is the sound that can be heard when snow begins to collapse, showing cracks next to snowshoes or skis.

The sound is made when air escapes through the snow because of the crack, Burns said. It’s common to see small cracks when you’re walking or treading new snow, “but if a crack runs 10 feet away from you, that’s not normal,” he said. “It’s a sign of instability. The snowpack is not happy, and something is going on.”

Diagram: Weight from people and machines adds pressure to the lower snow layer, causing the snow above it to drop and slide.

Rapid warming: Sunny skies after a storm that dumps several inches of snow can be welcome but could also be concerning, Burns said.

Rapid, significant warming after a cold start can make snow less stable.

“If you go in the morning and you have your layers [of clothing], and then midday you’re down to a T-shirt, then the snowpack is changing,” he said.

Diagram shows a rise in temperature may cause the snow to melt into water and weigh down the snowpack, making it unstable.

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What causes an avalanche?

Snow falls in layers, and avalanches occur when a layer is triggered and slides down steep terrain. Usually, this involves a weak layer — loose, often new snow that doesn’t stick together — and a strong layer that has been packed, sticking together.

“[The weak layer] is there, just waiting, and then a trigger can happen,” said Keating, who has 40 years of experience with avalanches. “It can be a skier, a snowmobiler — a variety of reasons can cause that layer to collapse.”

According to the National Weather Service, 90% of avalanches that lead to deaths and injuries are caused by the victims or their companions.

It’s unclear what caused Wednesday’s deadly avalanche, but experts believe a particularly dry winter in the western U.S. has increased hazards.

This week marked the first time since 1992 that the first avalanche death of a winter came after Jan. 1, said Simon Trautman, director of the National Avalanche Center.

“That points to to how dry it’s been to a large area,” Trautman said. “What happens is any snow on the ground becomes very week and is a [poor] surface for new snow to fall on.”

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This weekend’s forecast

On Friday, the Sierra Avalanche Center issued a backcountry avalanche watch from Saturday morning to Sunday morning in the central Sierra Nevada, between Highway 49 and Highway 4, including the greater Lake Tahoe area.

“New snowfall combined with gale-force winds will load already problematic weak layers buried in the snowpack and may result in widespread avalanche activity in the mountains,” the National Weather Service said. “Traveling in, near or below backcountry avalanche terrain is not recommended.”

During that time, areas at an elevation between 7,000 and 8,000 feet are expected to see up to 14 inches of snow, and higher areas could see as much as 24 inches, according to a winter storm warning issued by the National Weather Service.

The Sierra Avalanche Center maintains a daily avalanche forecast, which uses a five-point scale of risk from “low” to “extreme.” Friday was expected to carry “considerable” risk, the third point on the scale, and Saturday’s forecast is at the fourth point, “high.”

However, experts warn that the highest rating is not always the most dangerous.

“The most difficult rating to deal with is when it’s moderate, because that’s when you have to make your own decisions and look for the red flags,” Keating said. “When it’s high, you just stay away.”

Historically, most deaths have occurred when the risk level was considerable, according to the National Avalanche Center.

“That’s where people get caught,” Burns said. “It’s not an easy decision.”

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Equipment to carry

A few basic pieces of equipment — a shovel, probe and transceiver — could be helpful for people headed out to the snow, Keating said. They can be optional for those who are staying within a resort and in routes that are mitigated for avalanche safety but are a must for those headed to backcountry areas.

A transceiver can help pinpoint a person’s location under the snow after an avalanche, Keating said. A probe — a long, metal rod — can also be vital in determining the location and depth of someone buried in snow. The shovel is used to dig out.

After Wednesday’s avalanche at Palisades Tahoe, ski patrolers and resort guests used probes to find and rescue a snowboarder who was buried.

There have been 244 avalanche fatalities in the U.S. since the winter of 2013, according to the Colorado Avalanche Information Center. The majority involved people who were skiing, snowboarding and touring in backcountry areas or incidents in what is called “sidecountry,” when someone wanders beyond resort property into adjacent terrain.

Six skiers and snowboarders have died in avalanches on open resort runs over the past 10 years; three of these deaths occurred in a single 2020 incident at an Idaho resort.