Front Range
AvalancheSam Murray · Mar 25, 2019 · Front Range
Weather
Partly cloudy skies. Temperatures in the 30s. Aspect SE with irregular sun. Elevation approximately 11.500.
Snowpack
Apron of couloir faces directly south and had several inches of loose, soft snow, that appeared to be large stellar plate crystals mostly unaffected by wind. Elevation approximately (10,000 - 10,500). As we gained elevation in the couloir the aspect shifted to SE and the layer of new snow became much thicker (10,800 - 11,400). We encountered 18-24 inches of soft wind slab on top of a firm layer of melt freeze cycle snow. We boot packed up this soft wind slab assessing stability on the way. We ultimately decided that the most dangerous part of the route would be the upper bowl guarding the entrance. As we approached the final 100 feet of the couloir (11,400-11,500), the snowpack turned to pencil hard ice/snow from melt freeze.
Avalanche
The first rider dropped into the couloir with an avalung deployed but not in his mouth. He made it safely through the upper hard pack section where the couloir is steepest and most narrow. Then, the snowboarder and made 2-3 turns in soft snow before the wind slab broke and began to slide. The snowboarder who was caught shouted "SLIDE" twice. All party members on top heard this, and one skier was positioned directly above the mouth of the couloir and maintained a line of sight to the snowboarder in the avalanche as much as possible. The observing skiers only lost site of the snowboarder when he was underneath sliding snow. The snowboarder was caught and carried approximately 250-300 feet down the couloir before managing to self arrest and escaping on the skiers left side of the couloir. The rest of the snow ran straight down to the valley floor. The snowboarder quickly signaled up to group members that he was okay. He moved farther down the couloir and behind a cliff to a safe zone. Then, the other three group members made careful turns down the slide path and reunited in a safe zone. We estimated the crown of the avalanche to be 18-24 inches thick and 50-70 feet wide at the top. Staunch walls ran down the sides for at least 100 feet if not more. In debriefing the incident we identified several major factors that contributed to the avalanche. The first was underestimating both wind and temperature. Though we had attempted to gather accurate wind data for representative slopes in RMNP on Friday and Saturday nights, we were unable to find specific data for the Bear Lake weather station site. We used nearby sites as a reference which led to us vastly underestimating the amount of wind that the slope had experienced. We also underestimated how much the temperature would rise during the day. Though our party discussed warming, and one group member even expressed concern at the base of the couloir and suggested the possibility of turning around, other party members dismisses concerns of warming and we gained false confidence as we climbed the couloir and clouds came out. We also identified the upper bowl as the most likely area for a wind slab or cornice to form, and we neglected to properly assess stability in the main/middle part of the chute. We were not concerned with this area, though this was the part of the chute that had indeed built up a heavy soft slab. We also discussed heuristic traps. Three group members met up with a 4th solo skier in the couloir. Though we were concerned about the decision making of someone climbing this couloir alone, we appeared knowledgable and reasonable in his assessment of the snow. He expressed confidence in the snowpack and even mentioned that he had spoken with some local Estes Park guides that were friends of his and they had told him they thought the elevator shaft couloir was safe and had been skied several days before. We all buoyed each others confidence as we boot packed up what we shoot have known was a dangerously deep soft slab of snow.