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
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.
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Keywords: avalanche accidents, snow creep, buried surface hoar
Digital Abstract Not Available