Avalanche characteristics of a transitional snow climate -: Columbia Mountains, British Columbia, Canada

The focus of this study lies on the analysis of avalanche characteristics in the Columbia Mountains in relation to the local snow climate. First, the snow climate of the mountain range is examined using a recently developed snow climate classification scheme. Avalanche observations made by a large helicopter operator are used to examine the characteristics of natural avalanche activity. The results show that the Columbia Mountains have a transitional snow climate with a strong maritime influence. Depending on the maritime influence, the percentage of natural avalanche activity on persistent weak layers varies between 0% and 40%. Facet-crust combinations, which primarily form after rain-on-snow events in the early season, and surface hoar layers are the most important types of persistent weak layers. The avalanche activity characteristics on these two persistent weak layers are examined in detail. The study implies that, even though the 'avalanche climate' and 'snow climate' of an area are closely related, there should be a clear differentiation between these two terms, which are currently used synonymously. We suggest the use of the term,avalanche climate' as a distinct adjunct to the description of the snow climate of an area. The more encompassing term should also include information, such as typically important snowpack weaknesses and avalanche activity statistics, which are directly relevant to avalanche forecasting. (C) 2003 Elsevier B.V. All rights reserved.