How the Fatal GS Bowl Avalanche at Palisades Tahoe, CA, Happened and Why it Could Happen Again

On January 10, 2024, around 9:30 a.m., a massive avalanche occurred in the GS Bowl off the KT-22 chairlift at Palisades Tahoe, California. A search of the debris pile, estimated at 10 feet deep in some places, was conducted by over 100 people, including ski patrollers, resort employees, and members of the public. This tragic accident resulted in one fatality and three other injuries. While ski patrollers work incredibly hard to mitigate the risks of inbound avalanches, the risk can never be completely eliminated due to the nature of avalanches.

An avalanche forecast from the Sierra Avalanche Center that day showed that the danger was ‘Considerable’ at the time of the accident. The main problem was identified as a persistent weak layer caused by facets near the ground and buried surface hoar 1-2 feet down in the snowpack. Facets and surface hoar are types of ice crystals characterized by straight edges and sharp corners. These types of crystals are concerning to find in the snowpack because they are so weak relative to other types of snow crystals. Ski areas do a lot of work before the ski season and throughout the season to ensure these crystal types never form inbounds because of the enormous avalanche problems they can bring.

In addition to the facets and surface hoar, winds were gusting near 100 miles per hour at ridgetops, adding a significant snow load to the weakened snowpack. Palisades reported receiving 17 inches a few days earlier on January 7 and three inches on January 10, the day of the avalanche. This new snowfall added a considerable load to the weak layers present deeper in the snowpack, increasing the likelihood of an avalanche. SnowBrains contacted Executive Director of the Sierra Avalanche Center David Reichel via email about the GS Bowl avalanche, but he declined to comment.

Inbounds avalanches are exceedingly rare. The National Ski Area Association estimates a rate of less than one death per 60 million skier visits, with only a handful of accidents in the last ten years. Non-fatal inbounds avalanches occur at a much higher rate, but ski areas do not report them with any regularity. The extremely low fatality rate shows how hard avalanche mitigation teams work to reduce this inherent risk of skiing. For context, the overall fatality rate at ski areas is estimated at a little less than one death per million skier visits, more than 60 times higher than the fatality rate from inbounds avalanches alone.

GS Bowl is located skiers right of the KT-22 chairlift and is a north-facing slope. The avalanche occurred on the first day KT-22 opened for the season. As one of the most famous chairlifts in the country, Palisades Tahoe had been working hard to get KT-22 open and the public was eagerly awaiting the first runs of the season on this chair. Because very few people had skied the terrain in this area, probably just a few laps by snow safety teams, the snowpack resembled the backcountry snowpack as opposed to a more typical densely compacted inbounds snowpack. Based on observations and forecasts from the Sierra Avalanche Center, this means that there was very likely buried surface hoar present in the snowpack on many of the runs off the KT-22 chairlift, including GS Bowl. This weak layer likely caused the hard slab avalanche that resulted in multiple burials and one fatality. SnowBrains provided Palisades Tahoe with our analysis and conclusions about the likely presence of facets or buried surface hoars, but the resort declined to comment specifically on whether their snow safety teams identified these crystal types in GS Bowl before or after the incident.

The San Francisco Chronicle reported that Palisades had conducted avalanche mitigation with explosives on KT-22 on January 7 and 9 but not on the morning of January 10. Patrick Lacey, Public Relations Manager at Palisades Tahoe, told SnowBrains, “Our patrol team used explosives for avalanche mitigation on the Sunday and Tuesday preceding the opening of KT-22. However, On Wednesday, January 10th, they did not use any charges. Instead, they conducted a thorough assessment of the terrain, as is customary each morning, to ensure it was safe to open. Typically, we avoid using explosives when snowfall is minimal. Regardless of conditions, our team consistently performs daily evaluations of the slopes.”

Simply put, avalanches are caused by snow on the ground starting to move. Avalanches usually occur on slopes steeper than 30 degrees, a slope angle found on many double black diamond runs. Loose avalanches or sluffs, well known to many steep skiers, do not have any cohesion to them and look like snow tumbling over itself in a cascade down the slope. Slab avalanches, on the other hand, are a consolidated chunk of the snowpack that begins to move down the slope. These slab avalanches are mostly caused by the failure of a weak layer somewhere in the snowpack. The failure of this weak layer, or the trigger, can be caused by a number of sources, including the added weight of a skier, new snow, or warming temperatures. Once this layer has fractured, given a sufficiently steep slope, all of the snow above that layer will start to move downhill. Common weak layers include interfaces between old snow and freshly fallen snow, interfaces between old snow and wind-drifted snow that form wind slab avalanches, and certain weaker snow crystal types.

Palisades Tahoe has one of the country’s most extensive avalanche mitigation programs. “There are hundreds of avalanche paths at Palisades Tahoe,” Will Paden, former Ski Patrol Director for Palisades Tahoe, said. “[The resort] likely has more avalanche-prone terrain than any other ski area in the country. Our Ski Patrols … use more explosives than any other ski area in the country.” Modern ski patrols, of which Palisades Tahoe is certainly at the forefront, have a few different ways of tackling the avalanche problem. On the forecasting side, these include remote weather stations and daily observations of what is happening in the snowpack all over the mountain. On the mitigation side, the two main techniques are explosives and ski cutting.

Many skiers are familiar with hearing explosive blasts associated with avalanche mitigation at ski resorts. These explosives can include one, two, or four-pound hand charges, military surplus howitzers, Gazex exploders, which use oxygen and propane, and many other technologies. The idea is to create a shockwave in the snowpack that causes a propagating fracture in a weak layer, leading to avalanche release. Most of the time, explosives are more effective when they are detonated above the snow surface rather than on the surface or even buried beneath it. This is because an ‘air blast’ creates a wider spreading shockwave. Snow is actually quite good at dampening the shockwaves created by explosions on or under the surface.

The use of explosives for avalanche control in the United States dates back to February 1939. Douglass Wadsworth, the first snow ranger for the Forest Service, attempted to release an avalanche on Mt. Superior, Utah, during a large storm cycle in Little Cottonwood Canyon. Though his attempt at artificial release failed, a huge avalanche occurred in the same area the next day, burying Highway 210 under 14 feet of snow and cutting off access to Little Cottonwood Canyon and the town of Alta. From the start, using explosives in avalanche mitigation was not a sure thing.

From then on, a great deal of research went into figuring out how best to deliver an explosive blast to a potential starting zone with sufficient effectiveness and maximum safety for the avalanche technician. For much of the late 20th century, howitzers were a popular option for ski resorts and highways. Palisades Tahoe was an early adopter of using artillery at the ski area. There were even some tests done near Glacier National Park in the winter of 1960 using the sonic boom of an F-106 Delta Dart jet flying at Mach 1.2 at low altitude to try and remotely trigger avalanches. Though a few howitzers are still in operation, most ski areas rely on hand charges for their explosive mitigation work.

Jerrod Findlay, a former ski patroller at Park City Mountain Resort in Utah, described the mixture of science and art that makes modern-day avalanche mitigation.

“It’s tricky right? Sometimes you’ll go out there, put your shot in the standard place, and it clears out everything as you would expect…other times you’ll go in and maybe throw some shots or do some ski cuts and it didn’t really do much, but you feel like there was something in there. Sometimes you can just feel it in your skis that maybe there’s a weak layer there, or based on the forecast you thought there was going to be something there. So then you go back and do another lap and maybe try putting shots or ski cuts in different placements.”

Findlay said that The Canyons, now part of Park City Mountain Resort, has around 140 known slide paths, and during large storm cycles, up to 22 teams would be working starting from sunrise. The day would begin at 3 or 4 a.m. when the snow safety teams would show up and start looking at weather data and avalanche forecasts. Shortly thereafter, the ‘bomb donkeys’ would show up and start assembling the explosive charges or ‘shots,’ depending on how many the snow safety team anticipated needing for the day’s problem. The rest of the patrol would arrive around 5:30 a.m. and set off on their assigned avalanche control routes shortly before sunrise.

Along with an early start to the day, patrollers commonly have an early start to the season. Many ski areas bring staff in for the season as soon as snow is on the ground. “We go up to the known slide paths and just work back and forth breaking up that early season snow,” Findlay said. This boot packing or ski packing is an attempt to prevent persistent weak layers like facets from forming inbounds. Most resorts try to get avalanche terrain open to the public as early as possible in the season. No matter how much preseason compaction work or mitigation work ski patrols can do, the public can put “hundreds to thousands of tracks in a day…they’re breaking up those weak layers, they’re compacting the snowpack, they’re anchoring the snow to the bed surface.”

After a lot of this compaction work is done, most of the usual avalanche mitigation work for the rest of the season deals with new snow brought either by storms or wind. Those types of problems are more readily mitigated with explosives and ski cuts. However, the opening of new terrain is often the most dangerous time for inbounds avalanches. Nearly half of the inbounds avalanches that have happened in the last twenty years have been within 24 hours of the terrain opening to the public, according to a recent study published in the International Snow Science Workshop Proceedings.

The study’s authors concluded that the most likely explanation for why inbound avalanches occur is that mitigation measures, like explosives, do not always affect the right part of the slope. They pointed out, “Since a great deal of spatial variability in slab and weak layer properties exists in avalanche starting zones, finding trigger zones is challenging.” Once the terrain is open, the public has ample opportunity to explore all of the possible trigger zones. Findlay agreed, saying: “In a lot of ways, you’re fighting an invisible monster. Sometimes the 101st set of tracks is really unlucky.”

Findlay shared a story from his experience as a patroller, showing just how sensitive these trigger points can be.

“We were up at the top of this bowl in the spring, but we didn’t have any shots with us. There’s a bush right at the top of the bowl. We’re out kind of far on the edge because we don’t really expect anything to happen. My route leader is stomping around saying ‘nothing really seems to be going on here’ and she jumps up and down a few times. I’m three feet beside her near this bush and I say ‘Yeah I think you’re right’ and I jumped and tore out the whole bowl right beneath my skis. It took out this bowl that was 500 feet wide maybe and two feet deep. That was not what we were expecting at all.”

One of the biggest challenges avalanche mitigation programs run into is that there is no way they can hit every possible trigger point on a slope with shots or cuts. Sometimes, the right trigger point can linger for days or weeks on an unstable slope, as demonstrated in an inbounds avalanche at Big Sky Resort, Montana, in 2007. On December 26, 2007, skiers triggered a large avalanche in Liberty Bowl at Big Sky Resort, Montana. According to a case study, the avalanche was an estimated 250 feet wide, broke two to three feet deep, and ran down the slope for over 1,000 feet, resulting in a debris pile up to 13 feet deep in some places. Luckily, no one was caught in this avalanche. The snowpack conditions and mitigation work leading up to the Liberty Bowl avalanche demonstrate just how uncertain avalanche mitigation work can be.

Liberty Bowl opened to the public on December 15, 2007, and had light moguls throughout the bowl. Since opening, Liberty Bowl received a little over a foot and a half of new snow, and explosives had been used the previous two days leading up to the avalanche. Scott Savage, the author of the case study, estimated that 2,000 people had skied Liberty Bowl since it opened, 350 had skied the bowl since the last snowfall, and 150 people had skied the bowl on the day it slid. After the slide, ski patrollers found explosive craters in the bed surface, indicating that the shots they had placed penetrated all the way to the weak layer but had not initiated a fracture. The hypothesis laid out in the study was that all of the ski compaction happened to the new snow but failed to reach the layer of facets buried deeper in the snowpack.

Armed with explosives, experience, and sophisticated knowledge of snow science and weather, avalanche mitigation teams across the country work daily to reduce the risk of inbound avalanches. Without the countless bombs and ski cuts, we could never hope to ski the steep technical terrain we all associate with inbounds skiing. This joy of steep and deep powder skiing comes with a lurking danger. The hard work of ski patrols throughout the season can never completely eliminate the risk of inbounds avalanches because of their fickle nature.

The GS Bowl avalanche at Palisades Tahoe represents another such tragedy that resulted from the inherent risk of skiing. The first day of any new terrain, especially the legendary terrain serviced by KT-22, is usually a day of high stoke and good vibes. The GS Bowl avalanche adds another solemn example of how sometimes the first day on new terrain can be among the most dangerous. It is also a reminder of the severity of the work that avalanche technicians face daily.