International Snow Science Workshop Proceedings - Montana State University Library

Item: Avalanche Accident Case Study: Persistent Buried Weak Layer in the Central Idaho Mountains

• • Title: Avalanche Accident Case Study: Persistent Buried Weak Layer in the Central Idaho Mountains

    Proceedings: 2002 International Snow Science Workshop, Penticton, British Columbia

    Authors:

    • Doug Abromeit  [ Forest Service National Avalanche Center ]
    • Bozo Cardozo  [ Sun Valley Helicopter Ski Guides, Ketchum, Idaho ]

    Date: 2002

    Abstract: A helicopter ski guide died in an avalanche at 3:00 pm on February 10, 1996 while guiding clients on a large west-facing slope in the Smoky Mountains of Central Idaho. The ski guide, his clients, and several other guides and their clients had skied over one hundred runs in the vicinity and on the same slope prior to the accident. The avalanche measured nearly one half-mile wide and involved three chutes that are separated by counter ridges. Three other guides and sixteen clients were on an unaffected counter ridge when the avalanche occurred. The avalanche fractured on buried surface hoar and near surface facets. The avalanche varied from one foot to an estimated five feet deep and ran on 28 to 38 degrees slopes. Forty-eight hours of extreme avalanche hazard including many natural and human triggered avalanches followed the fatal accident. Prior to the February 10 avalanche, significant WNW winds on January 27 rapidly loaded slopes throughout the area and numerous large natural and artificially triggered new snow avalanches occurred. No avalanches were reported from February 4 through February 9. An “inverted” storm dropped several centimeters of snow and three centimeters (1.2 inches) of water equivalent from February 4 - 8. Temperatures rose from –16 degrees C (2F) February 2 to –1 degree C (30F) February 9 and then spiked to 5 degrees C (41F) at 2:00 pm February 10. Our paper will examine possible reasons why the deadly cycle occurred despite no overly dramatic weather event immediately preceding it, how the accident affected the local community including avalanche education, and possible ways to deal with similar events in the future.

    Object ID: issw-2002-194-199.pdf

    Language of Article: English

    Presenter(s): Unknown

    Keywords: avalanche accidents, snow creep, buried surface hoar

    Page Number(s): 194-199

    Subjects: avalanche accidents persistent weak layers central idaho mountains

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