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Show COMMENTS Rapid changes in temperatures, such as when the sun leaves or first strikes a slope, can decrease the stability due to increased stress. The ski check in the morning didn't release any slide, even though the under- layers were quite weak. The " Palivacinni" avalanche path includes six smaller slide paths, all of which can slide individually, in any combination, or all at once. The control plan indicates 12 shot points, and stresses that high explosives be used. An avalanche area of this size must be continually checked with explosives and penetrometer tests run so as to know what is happening in the lower layers. Perhaps a slope with such complex problems should be kept closed until spring. No. 61- 3 BRIDGER BOWL. MONTANA 31 December 1961 WEATHER FACTORS In I96I winter came earlier than usual to the Bridger Bowl area in Montana. Snow began falling early in October, and temperatures ranged slightly below normal through December. The usual alternate warm spells occurred sporadically until the end of December, interspersed with more light snow layers. By late December, three to six feet of wel1- stratified snow covered the slopes. There were at least five distinct, potential glide planes of icy snow present in this pack. On 31 December, twenty- four hours had elapsed since the most recent foot of new snow had fallen. The temperature had risen from just above zero to about freezing. The day was clear and bright with no appreciable wind. ACCIDENT SUMMARY Slightly after noon on 31 December, seven skiers, all expert ( six were or had been members of the Bridger Bowl Ski Patrol), approached the North Bowl area by traversing northward from the top of the upper lift of the main ski face. The North Bowl is well below the summit of the main mountain mass. The Bowl is divided from the regular ski hill by a small subsidiary ridge. At this time the Bowl was closed by the Ski Patrol, although warning signs had been drifted over. The seven men intended to ski to the Bowl partly because of the powder snow there and partly to test out the area. The lead man entered the more steep North Bowl area and skied into a 40 degree ( 82%) couloir. In doing this he started a surface sluff that carried him with it at least one hundred feet down the gully. The others, 67 |
