Item: Case Study: Natural Glide and Wet Slab Avalanche Cycle, Going-To-The-Sun Road, Glacier National Park, Montana USA
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Title: Case Study: Natural Glide and Wet Slab Avalanche Cycle, Going-To-The-Sun Road, Glacier National Park, Montana USA
Proceedings: International Snow Science Workshop 2016 Proceedings, Breckenridge, CO, USA
Authors:
- Jake Hutchinson [ National Park Service, West Glacier, MT, USA ] [ American Avalanche Institute, Victor, ID, USA ]
- Erich H. Peitzsch [ U.S. Geological Survey, Northern Rocky Mountain Science Center, West Glacier, MT, USA ] [ Snow and Avalanche Laboratory, Montana State University, Bozeman, MT, USA ] [ Department of Earth Sciences, Montana State Univeristy, Bozeman, MT, USA ]
- Adam M. Clark [ U.S. Geological Survey, Northern Rocky Mountain Science Center, West Glacier, MT, USA ]
Date: 2016-10-02
Abstract: The Going-to-the-Sun Road (GTSR) is the premier tourist attraction in Glacier National Park, Montana. The GTSR also traverses through and under 40 avalanche paths which pose a hazard to National Park Service (NPS) road crews during the annual spring snow plowing operation. Through a joint collaboration between the NPS and the U.S. Geological Survey (USGS), a forecasting program primarily dealing with wet snow avalanche problems serves to aid worker safety. The objective of this case study is to examine the meteorological metrics and snowpack characteristics leading up to a noteworthy wet slab and glide avalanche cycle that occurred 16-22 April, 2016 during a period of unseasonably warm and sunny weather. Continuous above freezing temperatures at upper elevations with daily maximum values reaching 10-15° C persisted for four days. The nearby Flattop Mountain SNOTEL station reported a steady loss of SWE of approximately 1.25 cm/day. River height and discharge on the Middle Fork of the Flat-head River (app. 20-35 km away from starting zones) increased from 1.26 m and 139.60 m3/s (4930 cfs), respectively, on April 18 to 1.69 m and 267.59 m3/s (9450 cfs) on April 22. The ensuing avalanche cycle began with three small glide avalanches on 17 April and culminated in three large wet slab avalanches that released on wet, basal facets. These wet slabs were triggered by glide avalanches releasing above and cascading over cliffs. Four of these avalanches crossed plowed sections of the road, resulting in a three day delay in plowing operations. Finally, this specific case was compared to previous statistical models for wet snow avalanches in this transportation corridor. Out of 12 avalanche days, the model correctly predicted six of those days as avalanche days. This case study allowed for a greater understanding of a wet slab and glide avalanche cycle that occurred during a prolonged spring warming event and can serve as a reference for future similar cycles.
Object ID: ISSW16_O3.02.pdf
Language of Article: English
Presenter(s):
Keywords: glide avalanche, wet slab avalanche, forecasting, Glacier National Park, Montana
Page Number(s): 66-73
Subjects: glide avalanche wet avalanche glacier national park, montana
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