Vail & Summit County
AvalancheDaniel MacDonald · Apr 23, 2019 · Vail & Summit County
Weather
From Frisco/Peak 1 weather and CAIC research for the Summit zone this morning, a solid refreeze occurred last night and my guidebook stated a delayed sun hit for this NE-facing, BTL (10.5K-9.2K) route. However, a rapidly-warming, still, full-sun morning likely sufficiently counteracted that, especially around the tight, rock-sided choke point at 9.6K'.
Snowpack
Quite a few roller balls and at least one very small loose wet I triggered and managed on the approach to the top of the gully. But was (perhaps overly) confident I could manage any loose wet and was not expecting wet slab risk given multiple days of solid refreezes. As well, I was more than a bit concerned about rotten snow risk in the lower elevation trees at skier's right that was the primary alternative to Hummingbird. Location, aspect and elevation captured above.
Avalanche
One very small loose-wet as I descended from Royal Mountain summit to the gully entrance at around 10:45-11am. There appeared to have been an earlier (much bigger) slide in recent days and I skied a mix of the bed surface and - when coverage was lacking - the trees at skier's right most of the way down without incident. At 9.6K' I saw the choke and was concerned I couldn't manage any loose-wet consequence here so headed toward the trees. I felt a collapse, although nothing slid out from under me or otherwise appeared to slide (at least in the direction I was facing). I continued to move slowly and cautiously toward the side and my route took me under the edge of a rock outcrop. As I was under it, the snow under my feet slid cohesively, but I was able to keep from being pulled down with it. The seemingly small, contained slab (thought it was possible it was simply rotten snow on top of unseen rock) slid through some brush and over some rocks. I took some observations/pictures of what I thought was maybe a small, isolated 1' slab (and accidentally dropped a glove that joined the avy debris down below) and finished my exit to the side and bushwhacked down about 100' through the trees to retrieve my glove. In taking a few more pictures from below where I retrieved my glove, I realized that it's possible that the slab propagated behind me quite a bit further across the full choke point (maybe 20'). Either that or it slid prior to me skiing the gully and I somehow missed the crown on the left as I descended...don't think so though given the picture as I'm not sure how I could have missed seeing that up to 2' crown spanning the full choke point. It's also possible that the first collapse I felt was that slide occurring and because I was facing away from it and focused on getting to the side of the gully I completely missed it. Again, doubt I could have missed that, but given the direction I was facing, maybe? Regardless of when it happened, that crown looks to be about 2' at it's deepest from the picture. In hindsight, despite the solid refreeze, skiing something late-morning with such a steep, tight, rock-sided choke at a relatively low elevation was unwise given the quick warming today. Location, aspect, elevation captured above.