Item: Depth Hoar, Avalanches, and Wet Slabs: A Case Study of the Historic March, 2012 Wet Slab Avalanche Cycle at Bridger Bowl, Montana
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Title: Depth Hoar, Avalanches, and Wet Slabs: A Case Study of the Historic March, 2012 Wet Slab Avalanche Cycle at Bridger Bowl, Montana
Proceedings: Proceedings, 2012 International Snow Science Workshop, Anchorage, Alaska
Authors:
- Alex Marienthal [ Snow and Avalanche Laboratory, Montana State University, Bozeman, Montana, USA ] [ Bridger Bowl Ski Patrol, Bozeman, Montana, USA ]
- Jordy Hendrikx [ Snow and Avalanche Laboratory, Montana State University, Bozeman, Montana, USA ]
- Doug Chabot [ Gallatin National Forest Avalanche Center, Bozeman, Montana, USA ]
- Pete Maleski [ Bridger Bowl Ski Patrol, Bozeman, Montana, USA ]
- Karl Birkeland [ USDA Forest Service National Avalanche Center, Bozeman, Montana, USA ] [ Snow and Avalanche Laboratory, Montana State University, Bozeman, Montana, USA ]
Date: 2012
Abstract: During this past winter, southwest Montana had many large avalanches and days of high avalanche danger. In the Bridger Mountains the most prominent and active weak layer was a 30-55cm thick layer of depth hoar. This layer developed in November 2011 and persisted throughout the season. Precipitation was below average between December and early February, but each storm consistently produced artificially triggered avalanches on this layer. Higher snowfall rates and above average SWE in late February and March produced natural avalanche activity in the backcountry on the depth hoar. In late March 2012 a near isothermal snowpack, combined with a period of above freezing temperatures and heavy snowfall, produced an historic skier triggered and explosive controlled full depth wet slab cycle on the depth hoar. This event occurred on in-bounds terrain that was closed at the time, and had previously been heavily skied and controlled with explosives. We will review meteorological and snowpack factors that were associated with avalanche activity on the depth hoar within Bridger Bowl ski area and in the surrounding backcountry. Weather data from stations at Bridger Bowl and snowpack observations taken throughout the ski area will be used to discuss the factors associated with the timing of avalanche activity on the depth hoar layer. Patterns, trends, and outcomes will be highlighted which may be of wider value to the industry in managing these types of instabilities in future years.
Object ID: issw-2012-062-068.pdf
Language of Article: English
Presenter(s): unknown
Keywords: bridger mountains, hoar layer, wet slab avalanche, dry slab avalanche, rain on snow
Page Number(s): 62-68
Subjects: snowpack properties weather conditions depth hoar layers
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