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<br />I) Normal snowpack at Wolf Creek Pass was defined as a linear <br />accumulation beginning with zero pack on October 1 to 18.1 inches <br />water content on February I and then to 20.8 inches water content <br />on February 15. Snowpack measurements for avalanche criteria <br />were the biweekly Soil Conservation Service readings at the Wolf <br />Creek Pass course I mile east of the summit. <br />2) Forecasts for two consecutive 24-hour periods were made for the <br />summit of Wolf Creek Pass. The first period was from 1100 MST <br />on the day the morning forecast was made and the second period <br />was for the following 24-hour period also from 1100 MST to 1100 <br />MST. Amount forecasts did not consider the seeding effects, only <br />the natural precipitation. The maximum forecast precipitation <br />amount for the highest of these periods was used in the avalanche <br />criteria. <br />3) A running lO-day total of actual accumulated precipitation recorded <br />at the highway building immediately west of Wolf Creek Pass summit <br />was maintained in the Durango Forecast Center. This preceding <br />lO-day total did not include forecast amounts as in 2) above. <br />A suspension appraisal of a potential experimental day was made each <br />morning prior to obtaining a random decision. This suspension appraisal was <br />updated at other time intervals during an experimental period from incoming <br />Project data. In no case did this time interval exceed twelve hours. <br />For the 1970-71 and 1971-72 seasons, depending on the suspension ap- <br />praisal, seeding was suspended for avalanche potential only between l6 December <br />and 31 January inclusive based on the following criteria: <br />1) There will be no suspension for avalanche when snowpack is less <br />than 90 percent normal unless the Colorado State Highway Depart- <br />ment advises that unusually hazardous snow conditions exist. <br />2) Snowpack 91 to 120 percent of normal, 24- hour maximum forecast <br />precipitation 2.0 inches or greater water content, and a preceding <br />lO-day accumulation of 4.00 inches or greater water content. <br />3) Snowpack 121 to 150 percent of normal, 24-hour maximum forecast <br />precipitation, 1. 0 inch or greater water content, and preceding <br />lO-day precipitation accumulation of 2. 50 inches or greater water <br />content. <br /> <br />~ <br /> <br />2-15 <br />