Our party of 2 was on our 5th skin up the "typical" skin track used to access God’s Lawnmower. We had previously skied the ridge line down to the “Slabs” and then skirted the far edge of the slabs, the treed ridge down to where it drops steeply to the left to the bottom of GLM, and then also nibbled into GLM proper, bypassing the classic chute entrance by using the trees on the right. Originally we stopped about 400 feet or so below the “typical” stopping point, then later pushed up higher by another couple-hundred feet. On our last ascent we were again about 400 feet or so below the “top” when a skinning step created a big whoomph that surprised us, but not as much as the subsequent 2nd whoomph and the snow that started rapidly moving towards us.
My partner was partly in the lee of a tree and I did a quick kick turn to try to lunge towards him but it was a fairly futile effort. Fortunately we were on the flank of the slide and trees above probably broke the power a bit, so the snow washed over me without too much oomph and I only traveled a few feet. Had I gone further I would have likely gone into a debris pile at a flatter spot above some trees (where my one ski ended up) that wasn’t that deep. However, out in the more-open terrain to skinner’s left the debris ran far and fast, and we think that it likely ran all the way down the slab shot below.
The thrust of the energy was on the more-easterly aspect; ie NOT on the GLM side and more on the Craig’s Chute side. Possibly due to the NW windloading from yesterday? It ran on the facet layer that – where we were – was 3’ deep. We did not carry on up higher to check out the top crown, but we could see quite a ways up and the remote trigger distance was impressive. And it appeared to propagate pretty far to the south across those chutes.
Most disconcerting was that there were approximately 13 sets of tracks in that area, and it had been skied (not much) yesterday. As everyone knows who has skied the last few days, the skiing was sublime, and it certainly didn’t “feel” like we were floating on a hard slab that was ready to run. We had no other signs of instabilities; the new snow was sloughing a little in the steeper trees but was barely noticeable, and a quick hand/pole pit - only about 2 feet deep, and not down to the facet layer, as it turns out - did not indicate any unusual instabilities.
Of note: most of the skin track was unaffected; ie the typical skin line up to the point where it starts to feel “real’ (steepness) was indeed in the safety zone relative to this particular slide. However, most of the upper skin track was taken out. We skied the bed surface down a ways and then realized that we should cut over to the skin line because the other party we had seen may have been ascending and gotten swept down and maybe a rescue might be necessary, but zigzagging deep in the old growth they were blissfully unaware that anything had happened. Of course, the last few hundred feet of the skinner takes one out of that safer zone and into steeper, more-open terrain where the slide occurred.
Added comments and pictures by: Trent Meisenheimer
Photo below is an overview of the Kessler Slabs where the avalanche ran through the trees and spilled over the cliffs. The black line is an estimate of the fracture line. The avalanche was 2-3 feet deep and roughly 250 feet wide, running close to 1000 vertical feet.
The snow pack structure is similar to other avalanches triggered in the past weeks. The avalanche failed on a layer of very small grained facets.
The general set up is this... Early December was abnormally warm and this allowed the snow to settle and gain strength, in some places a crust was formed on the surface. On December 11th a wind event was noted forming wind slabs in the higher terrain. Then we received a storm that brought low density stellar snow that faceted very quickly (Dec 14-15). On December 21-22 this layer was buried and preserved throughout most of the range.
In most of the recent avalanches there has been a crust below the small grained facets. However, that was not the case with this avalanche. I could not find any crust below the weak layer. There was a big difference in hardness between the weak layer and the bed surface.
I was not comfortable doing a crown profile as there was still hangfire above and adjacent to me. I did, however, dig a snow pit lower on the ridge in a safe location and that picture is below. The arrow points to the weak layer that failed.
