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Show when they have "blown themselves out over Alta and other alpine ski areas yet unnamed. Our observations on several of the avalanche factors are not accurate enough. To mention a few, there are snow settlement rates, wind direction, the amounts of snow transported by wind at different levels and different rates of snowfall-, snow weights, the effect of humidity. Of the facts revealed, four are outstanding; 1. The almost infinite variety of conditions which can produce avalanche conditions. 2. The strong preponderance of favorable factors necessary to produce dangerous avalanche conditions. 3. The importance of combinations of avalanche factors. U. The dominance of wind force as a contributory factor. Process of Avalanche Hazard Forecasting Obviously, the process of avalanche hazard forecasting is not simple and a different matter from recording avalanche data after the crisis is over. The hazard fluctuates from hour to hour and from one part of the area to another. Forecasting is a continuous process. During a storm, the snow ranger must keep a sort of mental box score of the avalanche factors. Fortunately for him, the hazard does not become critical all of a sudden. There are exceptions, but ordinarily an observer who knows his business is not taken by surprise. He is continually comparing his mental picture of the avalanche situation with conditions as he actually finds them in his test plots. * Field testing is an essential part of the process of forecasting. Long range weather prospects influence his decisions« The time of day must also be considered. A storm beginning in the afternoon will probably not become dangerous soon enough to affect the skiers, A stormy morning, with the Weather Bureau predicting no improvement, is an obvious hint to "batten down the hatches." Always he must keep several jumps ahead of the avalanche hazard. He can never forget that 2-hour time margin necessary for clearing the area. Although it makes difference to an avalanche whether there is anyone in the area or not, it does make an important difference to the snow ranger. The number of skiers on the slopes, the amount of traffic on the highway, the availability of shelter for everyone in case the road becomes impassable, whether or not he has communication with the highway foreman, the highway patrolman and other authorized officials who share his responsibility for public safety all influence the margin of safety which the snow ranger must allow. Whether a dangerous avalanche cycle does or does not occur is of secondary importance to the administrator of an alpine ski area. His concern is to -38- |
