Location: Kebler Pass Area
Date of Observation: 02/11/2019
Subject: skier triggered avalanches
Aspect: North East, East
I skier triggered R2.5D1.5 slide, would guess 150 feet wide, ENE aspect at around 10,400 feet Kebler/Town zone, trigger point probably right around 35 degrees, ran full track through sub 30 degree terrain, maybe 400 feet, running across a road cut and stopping at drainage bottom. We had witnessed one other skier triggered slide earlier in the day, R1.5D1, from another party, and thought we were moving to mellower terrain.
We discussed the reality that we were still skiing through an obvious start zone, but felt that the terrain was mellow enough that any instabilities would be localized in nature. The terrain did have a convexity on top that pushed just over 35 degrees but the rest of the terrain looked to be sub 30 degree. I was the first skier to drop. Just after skiing through the convexity in question, and noteworthy to say right when I felt like I had gotten past the potential trigger point, I saw the snow fracture in all directions under my feet. I immediately started traversing to my left toward my known safe zone. The snow was moving slowly and I didn’t feel all that endangered but I was surprised that as I traversed left the snow continued to fracture all around me and it took longer to get to my safe zone than I anticipated. Everything was still moving slowly when I got onto non-moving snow.
The slide continued over a second convexity, gaining momentum, and ended up running full track with speed and propagating to the left and right and developing a powder cloud. The avalanche ran through small trees but did not damage them, and we estimated the deposition pile to be around 3 feet deep as estimated on the road cut. Unfortunately I didn’t take the time to measure crown heights but from photos and memory would estimate to be between 6-18″. We do not believe it would have been deep enough to fully bury someone, but it ran fast enough to potentially cause serious injury in the handful of small trees it ran through at the bottom.
While we recognized and discussed the red flags we had already seen, we thought we were moving into manageable terrain. We obviously underestimated the potential for propagation and energy. See photos.