|Avalanche Type||Hard Slab||Aspect||West|
A very large avalanche was triggered in the Palmer Creek drainage on Sunday, March 26th. The avalanche entrained an entire bowl and sent debris over the Palmer Ck road, well into the valley bottom. It was triggered by the first skier on the slope, near the top of the bowl. No one was caught. The debris overran two of the groups snowmachines at the bottom of the path and the powder cloud was seen by various people in the area. Using safe travel protocol and a good dose of luck were both big factors in the positive outcome.
The report below is a compilation of the group involved and another group who witnessed the avalanche.
*A big thank you to all these people for sharing their information and photos. Another big thank you to those who arrived on scene to search the debris right after the slide.
|Avalanche Type||Hard Slab||Aspect||West|
Events of the day from a conversation with group involved:
A group of 4 snowmachine skiers left two snowmachines at the bottom of the bowl and continued, two per machine, up the Hirshey Mine gully to the ridge and north to the top of the bowl they were planning to ski (around 3,900' in elevation). Winds had scoured the upper ridges and two skiers were on rocks along the ridge under the high point with another skier posted on top of the bowl so all members could watch the first skier descend. This first skier made their way through hard wind effected snow to a preplanned relative safe zone. The moment the skier was getting to that safe zone a collapse was triggered and a very loud whumpf was heard by all. The slab fractured and released above the skier and sent debris on both sides of them, but did not hit the safe zone. The debris continued down slope, over benches to the planar slope above the road. Debris ran over the road and well into the valley below. One of the parked snowmachines was partially buried and other fully buried.
The day before the avalanche, a member of the group skied in this area with no signs of instability. The group noted that although they knew there were many large natural avalanches that occurred during the March 22nd storm, there was not evidence of recent natural avalanches from the past few days. On Sunday morning, they encountered 6 new inches of snow from the night before.
This was a hard slab avalanche that most likely released in faceted snow formed during the early March dry spell. It can be seen in the photos that it stepped down to older weak layers, increasing the volume of the debris. The crown varied from around 12' thick in a very wind loaded section at the top to only a couple feet or less thick in scoured areas. The dimensions are estimated to be around 1,000' wide in the upper bowl and 1,500' on the lower slope and running around 2,000' in vertical fall.
Original comments by person in the area:
Observed a very large avalanche as we were facing north in the back bowl of the Palmer Creek drainage. Avalanche reached across nearly the entire valley floor. Immediately rode over as our group (four snowmachiners) observed a group of four sled skiers in the morning riding the area. They were observed taking a common uptrack parallel to the Hirshey Mine switchback to access the ridgeline earlier in the day. Arrived to scene and was able to communicate with the group using radios on the common mountain frequency. They stated it was a remote trigger and all members of their party were accounted for. One member of their party observed on top of the ridge line above the crown. Two members of their party descended down after the trigger (ski tracks in photos). The other two took the uptrack down on their snowmachines. Two sleds were at the toe of the slope, one was partially buried and the other was completely buried. One member of our group conducted a beacon search across the valley floor and was joined by another group of two sled skiers who arrived on the scene after our group. No signals located. Briefly talked to the group while they were recovering their sleds and heard an extremely loud whumpfing from the slope above. Left area.
|Cracking (Shooting cracks)?||No|
Comments from person in the area:
Observed multiple smaller, natural wet loose releases throughout the morning at high elevations along ridgelines on south east aspects. Faint sounds of whumpfing could be heard in the afternoon (potentially not snow related). Older avalanche debris paths noted and visible throughout the entire drainage with the majority observed on the east side of the valley. Rapid rising of the temperature in the afternoon as the sun came out. Wind effected slopes observed throughout drainage.
Sunny early morning, little to no wind. Partly sunny later afternoon, no wind. Temperature was mid 20s (F) at trailhead at 10:00 AM and warmed up substantially throughout the afternoon.
Settled powder from the previous week with a high degree of wind effected snow along ridges.