CAIC: Colorado Avalanche Information Center

2019/12/08 - Colorado - Diamond Peaks, west of Cameron Pass

Published 2019/12/19 by Mike Cooperstein - Forecaster, CAIC


Avalanche Details

  • Location: Diamond Peaks, west of Cameron Pass
  • State: Colorado
  • Date: 2019/12/08
  • Time: 1:15 PM (Estimated)
  • Summary Description: 1 backcountry skier, caught, buried, and killed
  • Primary Activity: Backcountry Tourer
  • Primary Travel Mode: Ski
  • Location Setting: Backcountry

Number

  • Caught: 1
  • Partially Buried, Non-Critical: 0
  • Partially Buried, Critical: 0
  • Fully Buried: 1
  • Injured: 0
  • Killed: 1

Avalanche

  • Type: HS
  • Trigger: AS - Skier
  • Trigger (subcode): u - An unintentional release
  • Size - Relative to Path: R2
  • Size - Destructive Force: D2
  • Sliding Surface: O - Within Old Snow

Site

  • Slope Aspect: NE
  • Site Elevation: 11420 ft
  • Slope Angle: 36 °
  • Slope Characteristic: Sparse Trees,Gully/Couloir

Avalanche Comments

This was a hard-slab avalanche unintentionally triggered by a backcountry skier. The avalanche was small relative to the path, and large enough to bury, injure, or kill a person. The avalanche broke in a layer of faceted snow above a crust (HS-ASu-R2D2-O). The skier triggered the avalanche approximately midway through her descent near the center of a steep wind-loaded gully. The avalanche started on a northeast-facing slope at around 11,200 feet. It broke above the skier and although she managed to stay on her skis, she was swept down the gully and buried on a flat bench in the runout zone. The avalanche was a mix of hard wind slabs and soft storm slabs that broke on persistent weak layers. It broke about 300 feet wide and ran about 420 vertical feet. The avalanche debris was composed of hard snow and small blocks and was over 200 centimeters deep (about 7 feet) in some places. The debris pile was 375 feet wide at the toe and spread across two gullies separated by a small cliff band and sparse trees.

Backcountry Avalanche Forecast

The Backcountry Avalanche Forecast for the Front Range zone rated the avalanche danger as Moderate (Level 2) near and above treeline and Low (Level 1) below treeline. The forecast listed Persistent Slab avalanches as the primary problem on north through northeast to east-facing aspects near and above treeline. The likelihood of triggering was possible and size small to large. The Front Range Summary on December 8 read:

The most dangerous areas are previously wind-loaded slopes. In these spots you can trigger avalanches large enough to bury you. Look for signs of previous wind drifting like a hard snow surface or smooth, rounded pillows of snow. The drifted areas may be along gully walls or downwind of terrain features mid-slope. Cornices are an indication of wind direction, and that snow has drifted onto the slopes below. Use the indications to steer well around drifted spots on steep slopes.

Snowfall increases in the late afternoon and overnight. You may trigger shallow avalanches in the new snow where you find more that about a foot of freshly drifted snow.

Weather Summary

On December 8, skies were obscured with low cloud ceilings. Although weather stations only recorded one inch of new snow, other parties touring in the area reported periods of moderate snowfall throughout the morning, and rescuers reported periods of two inch per hour snowfall during the time of the rescue. Southwesterly winds averaged 13 miles per hour with gusts to 35. The visibility was less than a quarter of a mile.

Snowpack Summary

Snow that fell in late October turned into weak, faceted crystals at the ground, particularly on northerly and easterly-facing slopes near and above treeline. There was only about a foot of total depth  at the Joe Wright SNOTEL (10,120 feet) and the CAIC Cameron Pass weather station (10,574 feet) on November 20, 2019. Both stations are less than a mile and a half from the accident site. Brief periods of snow mixed with periods of sun left the snow depth at around two feet at the beginning of December. From December 1 to December 8, 2019, the area around Cameron Pass picked up about five inches of new snow. Southwesterly winds drifted snow from December 5 through December 8.

The slope where the accident occurred had variable snowpack depths and contained multiple weak layers. The avalanche broke across two gully features connected by a broad rib with sparse trees. The avalanche broke to the ground in areas with a thin snowpack like the rib or higher on the slope where wind-blown snow did not collect. Investigators estimated a snowpack depth of about four feet in the gully features. In the gullies, the bed surface was a hard crust on top of a thin layer of depth hoar. The avalanche likely failed in a layer of faceted snow just above the crust.

Events Leading to the Avalanche

Two backcountry skiers left Fort Collins on the morning of December 8 with the intention of skiing the lower angle trees below the southern Diamond Peaks. They checked the CAIC forecast the night before the accident and again before driving up State Highway 14 to Cameron Pass. The pair discussed the Moderate danger (Level 2 of 5) and felt that they had enough backcountry skills to travel at that danger in an area they had been over a dozen times prior. This was their first backcountry trip of the season and they planned to “take it easy”. 

Accident Summary

The pair arrived at the Cameron Pass parking lot around 11:30 AM. They ascended the normal skin track that winds up the runout of an avalanche path. They were feeling better than expected when they reached treeline at about 10,800 feet. They discussed going higher on Diamond Peaks, a change of their initial plans. They felt that the snow cover was thin and “that there was hardly any snowpack up there, just enough to ski.” They decided to climb to the southern summit of Diamond Peaks, assess snow conditions, and ski down a run commonly called the South Diamond Face.

They ascended the standard skin track up low-angle terrain between the Diamond Peaks. They headed south along the ridge toward the South Diamond Face. They dug a snow pit near the top of the run. They found a six to eight inch thick layer of “granular crystals” which they identified as a weak layer, under another six to eight inches of hard-packed snow. Discussing the snowpack, they felt the lack of snow depth would keep any potential avalanches small. They decided to continue.

They quickly dug another snow pit at the top of the proposed descent route and found a very similar snowpack. They had another discussion and decided that although there was some risk they were going to descend the face. They planned their descent and identified a safer location to regroup.

Skier 1 descended to the skier’s right side of the face. He stopped below a rocky area with shallow snow cover. He called Skier 2 over to his location. They decided that Skier 2 would ski the next section first and they would regroup past the runout zone.

Skier 2 skied to skier’s left into the gully. She was about 150 feet below Skier 1 when she triggered the avalanche. Skier 2 managed to stay upright on her skis. Skier 1 noted that the avalanche did not look very deep, maybe only up to the top of her boots. Skier 1 kept an eye on his partner as long as he could, but visibility was poor and she disappeared out of sight.

Rescue Summary

Skier 1 descended the avalanche path once the snow stopped. He was about three quarters of the way down the avalanche before he could see the toe. He expected to see his partner standing up in shallow debris. He did not see her.

Skier 1 knew that he was above Skier 2’s last seen location, so he turned his beacon to search. It took Skier 1 a minute to gather himself and focus on the search. He initially followed his avalanche transceiver to the right, where it was indicating the strongest signal, but quickly realized that he was moving in the wrong direction. 

Skiers 3 and 4 were touring together. They observed what was happening, turned their transceivers to search, and skied over to help. The three finished their coarse search about the same time and began their fine search.

Skier 3 and 4’s transceivers were showing low readings, so Skier 1 assembled his probe and started probing in a grid pattern. Skiers 3 and 4 quickly joined him probing. They struck Skier 2’s helmet with a probe and began digging. Skier 1 estimates that the whole process took over 15 minutes and knew that “the situation was not good.”

They uncovered Skier 2’s face buried under about two feet of avalanche debris. She did not have an air pocket. They cleared the snow away from her face and out of her airway. She was cyanotic. Skier 1 attempted to give rescue breaths while the others continued to dig.

The avalanche had buried Skier 2 in a standing position and her skis did not release. The three decided Skier 4 would ski out for help. Skier 1 and 3 continued to dig. Skier 1 continued to deliver rescue breaths, but could tell it was not working well because of Skier 2’s position. They had to dig more than six feet deep before they could free Skier 2 from the debris. Once free, they pulled Skier 2 away from the slide path because they were concerned for their safety below the portion of the slide path that had not released. Additional backcountry tourers joined the efforts and assisted with CPR. One of the additional rescuers had a packable toboggan. The group elected to evacuate Skier 2 to the parking area.

There is no cell phone service at Cameron Pass; however, Skier 4 flagged down a Colorado Department of Transportation maintenance worker who radioed for help. Jackson and Larimer County emergency services were notified around 2:45 PM. Deputies from the Jackson and Larimer County Sheriff along with Rangers from Colorado State Forest State Parks and EMS services responded to Cameron Pass.

Comments

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.

Snow Pits and Snowpack Variability: The two skiers dug a snow pit near the top of the run that they wanted to ski. They correctly identified a slab on top of a weak layer near the ground. They knew that the structure was poor, but the total height of snow where the dug the pit was only 12 to 14 inches. They incorrectly assumed that the snowpack across the entire slope would be 12 to 14 inches deep, and that if they triggered an avalanche it would not be very big. Snow profiles and snowpack tests are useful tools to examine the snowpack structure and identify weak layers; however, use great care in extrapolating a snow profile to an entire slope. In this case, the snowpack on portions of the slope was only 12 to 14 inches deep, but the gully where Skier 2 triggered the avalanche was a perfect place to collect wind-drifted snow. The snowpack was much deeper in the gully and the avalanche wider and deeper than the pair expected.

Terrain Traps: Terrain traps are features that increase the consequence of getting caught in an avalanche. The gully feature concentrated the avalanche flow. The transition to lower angled terrain allowed avalanche debris to pile deeply. Skier 2 was buried upright at the slope transition, in the deepest area of debris. It took considerable time to dig Skier 2 free, and her upright position significantly complicated first aid efforts. 

Moderate Avalanche Danger: Skiers 1 and 2 took the important steps of reading the avalanche forecast and discussing the potential avalanche problems. However, recreationalists have a tendency to underestimate a Moderate (Level 2 of 5) danger. Almost 40% of avalanche fatalities in Colorado occur at a Moderate avalanche danger. The North American Avalanche Danger Scale describes that natural avalanches are unlikely and human-triggered avalanches are possible in specific areas at a Moderate danger. The travel advice for a Moderate danger says to “Evaluate snow and terrain carefully; identify features of concern.” One of the features of concern highlighted in the avalanche forecast was northeast facing slopes near and above treeline, particularly previously wind-loaded areas. Skier 2 triggered the avalanche in a wind-loaded northeast-facing gully. 

Media

Images

Snowpits

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Figure 7: Generalized snow profile at the crown of the accident. At the deepest part of the crown the avalanche broke around 80 cm deep on the buried faceted crystals. In the track the avalanche broke at the top of the hard crust layer about 10 cm from the ground.