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Show note that three major avalanche paths ran within approximately one hour. Two vehicles were caught, involving seven people. Highway use increases eacy year, with the result that the odds of highway avalanche fatalities are also increasing. No. 62- 2 NEAR BRIDGER BOWL, MONTANA January 1962 WEATHER FACTORS Weather conditions preceding the day of the slide are unknown. Heavy snows had occurred early in the season, ( October and November). On the day of the slide, a heavy, wet snowstorm was in progress, with an accumulation of well over one- foot of fresh snow. Temperature was steady at about freezing. Wind was very 1ight. AVALANCHE DATA The avalanche occurred at approximately 3: 00 p. m. on a day in late January, involving a prominent spur two miles north and west of Bridger Bowl. The slide took place immediately below, but not involving, a party of five, led by C. B., which had just completed a ski ascent of the crest of the Bridger Range by way of a northeast running spur. The party attempted to anticipate avalanche conditions. Artificially induced slides on very steep slopes indicated that powder snow avalanche conditions were building up rapidly. Appropriate precautions were taken: the party avoided very steep slopes and proceeded one person at a time over questionable areas. The leader made numerous ski pole probes in a determined effort to anticipate slab conditions. These attempts did not reveal the hazardous hair- trigger conditions existing below the firm sub- crust. The situation was similar to the conditions existing prior to the avalanche in the same area in early February, I960 ( See Report No. 60- 4). In this case also, pole probing did not penetrate the sub- crust and reveal the fragile depth- hoar adjacent to the ground. Just as the trailing members of the party reached the crest of the Bridger Range, a distinct, deep " crunch" was heard and felt in the snow. A thin fracture appeared to the skiers close to their position and showed a vertical displacement of about two inches. This gave definite warning of slab conditions. Since a descent had to be made, the leader gave a general warning to move quickly and singly across all open slopes on the way down, and for the party to keep together by assembling on minor spurs from time to time. The warning was unnecessary, however, for the avalanche had already occurred below the party at the line of maximum convexity. It was 70 |