The Colorado Avalanche Information Center has published their full report on the backcountry avalanche that killed two skiers in the San Juan Mountains on February 25th.
We initially reported on the incident here.
Our thoughts and condolences are with the friends and family of the deceased.
Please read the full report by CAIC below:
The avalanche occurred on a below treeline northwest-facing slope near Vallecito Reservoir. It was unintentionally triggered by backcountry skiers. It was medium-sized relative to the path and produced enough destructive force to bury, injure, or kill a person. The avalanche broke below a firm melt-freeze crust in a layer of faceted snow grains and stepped down to the ground across the steepest portions of the slope (HS-ASu-R2-D2-O/G). The avalanche was 12 to 30 inches deep and about 200 feet wide at the crown face. It ran about 300 vertical feet through a burn scar, stumps, small aspens, and thick willows .
Backcountry Avalanche Forecast
The Colorado Avalanche Information Center’s (CAIC) forecast for the area around Vallecito Reservoir on Saturday, February 25, 2023, rated the avalanche danger at Considerable (Level 3 of 5) near and above treeline and Moderate (Level 2 of 5) below treeline. The primary problem was Wind Slab avalanches on all elevations on northwest through north to southeast-facing slopes. The likelihood was Likey, and the expected size was Small to Large (up to D2). The second problem was Persistent Slab avalanches near and above treeline on west through north to east-facing slopes. The likelihood was Possible, and the expected size was Large (D2). The third problem was Loose Wet avalanches at all elevations on east through south to west-facing slopes. The likelihood was Likely, and the expected avalanche size was Small to Large (up to D2). The summary statement read:
The most dangerous areas are wind-loaded slopes. Southwest winds drifted the new snow into thicker slabs on northerly and easterly-facing slopes. Strong and erratic winds built dangerous drifts lower in the terrain than usual, and on wide open slopes below treeline. Avalanches in the new snow could break into weaker snow layers three to four feet deep on slopes facing west through north to east. Avoid areas where you see evidence of recent wind drifting such as fresh cornices, rounded pillows of snow, or a hard, sculpted snow surface. If you experience cracking or collapsing, retreat to slopes around 30 degrees that are sheltered from the wind.
With a plethora of fresh snow on sunny slopes, Saturday’s warm-up may trigger a shed cycle of the new snow from east through south to west-facing slopes during the day. Traveling on steeper slopes with about 8 inches of wet snow increases your chance to trigger a loose avalanche. Move to less steep slopes if you sink past your shins into wet snow or see fresh rollerball activity.
The Vallecito SNOTEL site is 8.5 miles north-northeast of the accident site at 10,880 feet. The site recorded continuous snow from October 23, 2022. The snow was early and deep for the time of year. Total snow water equivalent (SWE) remained above the 30-year reference period median through most of November, then dropped to 69% of the median in late December. January was unusually snowy as a series of storms increased snowpack depth. By the month’s end, the total SWE was 139% of median. Between February 14 and 25, storms added 25 inches to the total snowpack depth. On February 25, the total SWE was 144% of the 30-year reference period.
The Big Bear Park RAWS station is about 12 miles northwest of the accident site at 10,341 feet. Maximum air temperatures were above freezing February 10 through 12, with total solar radiation consistent with clear skies. Between February 12 and 25, wind speeds were between 5 and 15 mph, with gusts to 56 mph on the 22nd. Winds were mainly from the southwest, but the period included days with northerly and easterly winds. On February 25, winds were gusting to 28 mph from the southeast, and the maximum air temperature was 35 F.
The snowpack in the southern San Juan Mountains was shallow and almost entirely composed of faceted crystals before it was buried by January snowfall. During dry weather in late January and early February, faceted crystals developed at the snowpack surface. At the avalanche site, investigators found a thin crust that likely formed during the warm days in mid-February above these faceted grains.
Snowfall in mid-February and strong to extreme southwesterly winds led to several avalanche cycles in the southern San Juan Mountains. The CAIC issued Avalanche Warnings for the forecast zone including Vallecito Reservoir on February 15 and 16 and again on February 22 through 24. Snow drifted into locations lower in the terrain than usual and onto open slopes below the treeline through this period.
Events Leading to the Avalanche
Skiers 1 and 2 met around 7:00 AM for a morning of backcountry skiing near Vallecito Reservoir. Skier 1 told his spouse “we will be returning by noon.”
There were no witnesses to the avalanche.
Skier 1’s spouse reported the two skiers overdue on the evening of February 25. La Plata County Search and Rescue (LPCSAR) began to mobilize at 9:18 PM. La Plata County Sheriff’s deputies located the skier’s car at a trailhead on CR501A just north of Vallecito Dam. Cell phone forensics and maps the skiers reviewed before leaving suggested they intended to ski south of the reservoir.
A Flight for Life helicopter began searching the area south of the dam around 11:30 PM. The flight crew used night vision goggles and spotlights. They found an avalanche and could see ski tracks going into the area, but not exiting the debris. The crew detected intermittent avalanche transceiver signals from the air.
A team from LPCSAR followed the skier’s tracks to the avalanche. Searchers saw a single ski near the toe of the avalanche debris. They conducted an avalanche transceiver search and located Skier 1 at 3:36 AM. Skier 1 was buried under about four feet of debris. Skier 2 was buried directly below. Upper Pine Fire Protection District personnel recovered the skier’s bodies on February 26, 2023.
Multiple agencies were involved in the search and recovery, including the La Plata County Sheriff’s Office, La Plata County Search and Rescue, Flight for Life Lifeguard 5, and Upper Pine Fire Protection District.
All of the fatal avalanche accidents we investigate are tragic events. We do our best to describe each one to help the people involved and the community as a whole better understand them. We offer these comments in the hope that it will help people avoid future avalanche accidents.
There were no witnesses to the avalanche, so everything we know about the event comes from looking at the skier’s tracks and equipment. At the site, we found ski tracks consistent with ascending but not descending. Both skiers had climbing skins on their skis when the avalanche caught them. They both carried avalanche transceivers, shovels, and probe poles. They both wore avalanche airbag packs. The trigger on each pack was still zipped inside the shoulder strap and neither had deployed their airbag. The skiers were buried together below the steepest portion of the slope.
Backcountry travelers often manage their exposure to an avalanche hazards by carefully choosing the terrain they travel through. There is always a chance of getting caught in an avalanche any time you are on or under a snow-covered slope that is steeper than 30 degrees, so spending less time in this kind of area reduces your chance of getting caught in an avalanche. Ascending a ski run often takes much longer than descending. So one common approach is to climb through low-angle terrain, even when planning to descend a steeper slope. It appears that Skiers 1 and 2 were ascending a steep portion of the slope (around 40 degrees), which put them in avalanche terrain for an extended period.
Another way to reduce the chance of getting killed in an avalanche is to carry rescue equipment. Avalanche transceivers make you searchable, so other people can find you if you’re buried in an avalanche. Airbag packs can keep you on the surface of avalanche debris. Both may help you survive an avalanche if you misjudge the hazard and get caught.
Skiers 1 and 2 were very experienced backcountry tourers. They carried all the right avalanche rescue equipment. However, the triggers on their avalanche airbag packs were not at the ready so they could not deploy their airbags to keep them on top of the debris. It also appears that they were traveling very close to each other, so when the avalanche released they were both caught and buried. Even though they had all the right gear, since they were both buried, there was no one around to effect a rescue.
This begs the question, why did this happen to two experienced and well-equipped backcountry travelers? Unfortunately, we will never know the details of their decision-making, however from the evidence we collected we can speculate that they did not think they were in a dangerous area. If they had, they probably would have approached the situation differently. They probably would have chosen a different route and they would have had their airbags ready to deploy.
We don’t know anything about these skiers’ thought processes or about any assessment they made of the snowpack or avalanche danger. We did not find evidence of any recent snowpits in the area. The upper layer of the snowpack was generally supportable, but we occasionally broke through as we traveled – which is an indication of a stronger layer over weaker snow. Without knowing what the skiers observed, we cannot completely understand the decisions they made.