Vail & Summit County
AvalancheJason Konigsberg · Feb 15, 2024 · Vail & Summit County
Weather
The day started mostly clear with quickly increasing clouds. Winds were strong but not moving additional snow. This changed around noon. Skies became obscured and there were periods of inch-an-hour snowfall. Winds were drifting the new snow.
Snowpack
At the low end of the BTL elevation band (8k to 10k), the snowpack is quite springlike with a conglomerate of hard supportable crusts making up the snowpack. Above 10k feet, was more winterline but still quiet in sheltered areas. The snowpack generally lacks a slab over the two weak layers described in the summary. I did not get any propagating results in stability tests in areas unaffected by the wind. I mostly tested east-facing slopes. Southerly slopes at the upper end of BTL and into NTL have very hard crusts underneath small amounts of snow. Near treeline east and northeast-facing slopes were receiving drifted snow today and there were fresh drifts from Wednesday's wind.
Avalanche
I remotely triggered a wide avalanche on an east-facing slope that wrapped around to the northeast. It looked like it broke about a foot deep and was 200 feet wide. I wasn't able to see a lot of it due to visibility. I was able to get down to a lower-angle east-facing portion of the slope that had a large crack in it but didn't slide (see media). I found 1 mm faceted crystals on top of a hard melt-freeze crust. This crust/facet combo was 40 cm from the surface. This was the failure layer. There were fragments of surface hoar, but this wasn't the culprit in this avalanche. I didn't get over to the northeast portion of the avalanche so it's possible that I would have found a more reactive, intact surface hoar layer in that shadier part of the start zone. I coded the avalanche as a D2, though it could have been smaller (D1.5). It was really hard to tell with the visibility.