Item: Warm Storms Associated with Avalanche Hazard in the Sierra Nevada
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Title: Warm Storms Associated with Avalanche Hazard in the Sierra Nevada
Proceedings: Proceedings of the 1998 International Snow Science Workshop, Sunriver, Oregon
Authors:
- Randall Osterhuber [ Central Sierra Snow Laboratory, Soda Springs, California ]
- Richard Kattelmann [ Sierra Nevada Aquatic Research Laboratory, Mammoth Lakes, California ]
Date: 1998
Abstract: Rain-on-snow events occasionally produce avalanches of varying magnitude depending on both snowpack properties and storm characteristics. Under rain-on-snow conditions in the Sierra Nevada, avalanche release appears to be most likely if new snow falls a couple days previous to the rain. In contrast, if the snowpack has already transmitted liquid water from the surface to the base, then even large amounts of rainfall rarely produce significant avalanches in the Sierra Nevada. Winter storms in this mountain range typically have rain/snow levels between 1200 and 2000 m. Warm storms with higher rain/snow levels of up to 2500 m occur a couple times in most winters and have the potential to generate rain-on-snow floods and wet-snow avalanches. This paper describes the characteristics of warm storms that had the potential to generate wet-snow avalanches. It also examines the frequency of rainfall following within three days of snowfall, which tends to be a hazardous combination. A case study of a very warm storm at the beginning of 1997 describes snowpack response to rainfall at high elevations where such warm storms have rarely been observed. At the snow research station at 2930 m on Mammoth Mountain in the eastern Sierra Nevada, air temperatures exceeding 4° C and 220 mm of rainfall was recorded. Although few avalanches were observed during this storm, flooding was severe throughout much of the range.
Object ID: issw-1998-526-533.pdf
Language of Article: English
Presenter(s): Unknown
Keywords: avalanche, avalanche frequency, rain-on-snow, snow stability, wet-snow avalanche
Page Number(s): 526-533
Subjects: snow stability wet avalanche avalanche release
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