Vail & Summit County
AvalancheAndrew McWilliams · Nov 27, 2024 · Vail & Summit County
Weather
S-1 and moderate WNW winds. Temperatures were in the teens with small windows of sunshine.
Snowpack
There was about 50-70cm of storm snow in this area and ski and boot penetration were through the new snow and into the old. When I left the skin track I got rumbling collapses in meadows. On the westerly slopes I ascended, I had few collapses or cracks. On recently wind-loaded slopes, I was able to easily kick new cornice and get some cracking in the new snow - I made a very small avalanche within the new snow just below a cornice on a southeast-facing slope. I went to look at a steep east-facing slope, when I got close there was a long shooting crack at the ridge which didn't avalanche because the slope angle reduced quickly. I heard a loud collapse and I may have triggered a large avalanche. I observed three large debris piles in the valley, but the slope had a blind rollover so I couldn't see the actual slide and felt unsafe descending to get a better look. On this steep near and above treeline easterly-facing slope, there was evidence of multiple small to large natural avalanches that likely ran sometime on November 26. I dug snowpits on west-facing slopes below and near treeline and a near treeline south-facing slope. There was a denser layer of wind-packed snow in all of the pits just below the storm snow. I noted a density change in the middle of the storm snow layer and got repeated non-propagating results in Extended Column Tests (ECT). The south-facing pit, had melt-freeze crusts on either side of the wind-packed layer. Below that were four-finger hard, (on the Hand Hardness Scale) small faceted grains. There were no other results in column tests in this pit. On the west-facing slope there were a variety of results on the basal facet interface - from no results to propagating results. Between the lack of avalanche observations, cracking/collapsing, and the pit results on this aspect, I think the basal facet layer lacks continuity across the slope. You can find a place on a west-facing slope where all the ingredients for an avalanche are there, but they're not as well distributed as on a northeast or east-facing slopes.
Avalanche
I saw multiple D1-2 avalanches on northeast and east-facing slopes near and above treeline. The light and additional snowfall after the slides made it difficult to get good imagery and determine the bed surface.