Avalanche: Turnagain

The avalanche appears to have failed on some kind of weak layer within the upper 3' of the snowpack that became reactive during the intense solar heating that was impacting the area in the 1-2 hours prior to the avalanche being triggered. Based on observations from elsewhere in the forecast zone the weak layer could be buried surface hoar or near surface facets that formed quickly between storms in the past few weeks. We think it is most likely that some kind of persistent weak layer was involved based on the wide propagation. The depth ranged from 1-3' deep with an average depth of roughly 2' and width of 100' based on photos. The debris at the toe of the avalanche was composed of a mix of some hard blocks of snow and softer snow. The avalanche was a size D 2-2.5 on the destructive scale, which means it is large enough to bury, injure, or kill a person.

The group skied off the south side of Tincan and approached the library by skinning up Tincan Creek in close proximity to two other groups. The three groups in the area coordinated where they would ski to try and avoid travelling on the same feature in order to minimize the hazard caused by other groups travelling overhead. At 1-2 pm the other groups in the area noted that the sun was starting to have a significant effect on the surface snow and natural loose snow avalanches were starting to release. At this point the group that triggered the avalanche was already climbing towards the top of the library. As they neared the top a cloud layer developed which obscured the terrain below them and left them with limited visibility during the descent.

Due to the poor visibility they decided to ski the run in pitches so that they could maintain as much visibility as possible within the group. They used radios to communicate within the group and coordinate their movements. The first skier descended part way down the face and stopped on a ridge feature just above the upper part of the avalanche crown (which had not been triggered yet). The second skier then descended down to the first skier so that he would be in closer contact in case skier 1 triggered an avalanche during their descent. Skier 1 then resumed travelling down slope and radioed back that he was clear of the steep terrain. Skier 2 then had skier 3 descend down to his position above the crown so they could maintain close contact. Once skier 3 arrived at his position skier 2 descended a few hundred feet over the steepest part of the run where they were concerned about the potential for wind slabs. Skier 2 stopped at another relatively flatter spot along a ridge and waited for skier 3.

Skier 3 triggered the avalanche from just below the first group up spot, after the first two skiers had already descended that same slope. Both skier 3 and skier 2, who was waiting below, were caught in the avalanche. Skier 3 pulled her airbag and mostly stayed on the surface during the avalanche and even said the airbag helped absorb some impacts on the way down. She noted that the motor fan for her airbag came back on a second time during her descent to keep the airbag fully inflated. She ended up on top of the debris and was not buried, likely thanks to her use and deployment of the airbag. Skier 2 did not have an airbag and was caught in the moving debris. Due to the steep terrain he found himself airborne at one point and collided with the gully walls on his descent. He sustained broken ribs as a result of the incident. The fourth member of the party, who was ~15' above the crown, watched skier 3 take a couple turns then saw the slope fracture, catching skier 3 and they disappeared into the cloud. Skier 4 was quickly informed via radio that both skiers caught in the avalanche were okay and was able to descend the bed surface.

Skier 2 came to rest with his head facing down slope about 50-100' below skier 3. He was partially buried with the right side of his body and his head under the snow and the left side of his body above the snow. He was able to reach his hand to the surface and extract himself from the debris. The shallow depth of his burial is at least partially due to the fact that the runout zone of the avalanche path is a large fan, which tends to spread out debris in a thinner layer instead of concentrating the debris into a deeper deposit. If this avalanche had occurred over a terrain feature that lead to a deeper deposit the outcome could have been much worse.

After extracting himself from the debris and communicating with his party he radioed to the two other groups in the area that they were okay and did not need assistance with a rescue. Skier 2 and skier 3 both lost skis, poles, and other equipment during the slide but were able to recover the majority of it before exiting the area. The group attributes the use of radios as a major asset during the incident. Skier 4 was able to collect three skis and pole on the descent, the fourth ski was found below the debris. Two additional poles were recovered nearby so the only gear lost was one pole and sunglasses. They were able to communicate within their own group and with other groups in the area quickly and avoid the confusion and chaos that can come with this type of incident response.