Item: HISTORIC WET SLAB AVALANCHE IN POST SEASON AT YELLOWSTONE CLUB: TIMING, RESPONSE, ANALYSIS, AND IMPLICATIONS
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Title: HISTORIC WET SLAB AVALANCHE IN POST SEASON AT YELLOWSTONE CLUB: TIMING, RESPONSE, ANALYSIS, AND IMPLICATIONS
Proceedings: International Snow Science Workshop Proceedings 2023, Bend, Oregon
Authors:
- Doug McCabe [ Yellowstone Club Ski Patrol, Big Sky, Montana, USA ]
Date: 2023-10-08
Abstract: In May of 2020, a very large, natural wet slab avalanche occurred in-bounds at the Yellowstone Club Ski Area after the ski area had ceased operations due to the COVID-19 pandemic. This event involved six known, mapped avalanche paths. Results of the investigation of the meteorological and snowpack factors that produced this avalanche, as well as the initial response to the avalanche, will benefit avalanche forecasters and snow safety workers. First, this paper examines the weather and associated snowpack stratigraphy leading up to the avalanche. Then the author identifies the R5-D3.5 avalanche's characteristics. The weather over the eight days preceding the event is highlighted. The combination of multiple remote weather stations, with the closest being within 75 meters of the avalanche site, and frequent in situ snowpit observations throughout the season, allow for a detailed analysis. Notably, an unusual combination of events—a significant cold, wet spring weather pattern followed by sustained, rapid warming without overnight freezing—essentially mimicked a rain-on-snow event on a delayed timeline. While this was the largest observed avalanche at the Yellowstone Club, no one was caught and damage to infrastructure was minimal. Wet slab avalanches of this magnitude are poorly understood and difficult to predict. However, they pose a significant threat to human life and property. The author hopes the analysis of this event will help further the avalanche community's understanding of wet slab avalanches and can improve wet slab forecasting.
Object ID: ISSW2023_P2.18.pdf
Language of Article: English
Presenter(s): Doug McCabe
Keywords: wet slab avalanche, avalanche forecasting, ski area operations.
Page Number(s): 745 - 750
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