Vail & Summit County
AvalancheAndrew McWilliams · Dec 7, 2023 · Vail & Summit County
Weather
Warm and windy with building clouds. Temperatures reached the high 20s and the wind was from the west. Average hourly wind speeds felt light, but there were lots of strong gusts.
Snowpack
Lots of loud collapses as I ascended north and northeast-facing slopes. I noticed these starting just above 11,000 feet where the wind had made the surface slab denser and they continued until the snow ran out on the ridge just above 12,000 feet. Above treeline in this area has discontinuous snow coverage. There is far more consistent snow cover near treeline. Snow depths near treeline were about 50cm to 80cm. There were fewer collapses on the easterly-facing slopes I traveled, and I heard none above treeline, but once I descended closer to the trees the snowpack was talkative again. A snowpit on a southeast-facing slope at about 12,100 feet had two denser wind slabs resting on facets above a melt-freeze crust which capped the depth hoar layer. The depth hoar layer was thin and the crust was decomposing. I found propagating Extended Column Test results associated with the wind-packed layers. As I egressed back into the valley, I noticed an avalanche that had propagated widely on the same slope. The bed surface was getting filled back in with wind-blown snow, but it seems like this slide ran on the melt-freeze crust/facet interface close to the ground. The debris was hard and I imagine this slide ran sometime around the 3rd or 4th of December - at the tail end of the storm when the winds picked up. Although my snowpit did not have results at this interface, this slide tells me that our Persistent Slab avalanche problem is present on southeast aspects.
Avalanche
The debris was already getting filled in by the wind, but this slide likely ran sometime between 12/2 and 12/5.