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<br />~ <br /> <br />4) Snowpack 151 percent of normal or above, 24-hour maximum forecast <br />precipitation of 0.7 inch or greater, and a preceding 10-day preci- <br />pitation accumulation of 1. 75 inches or greater water content. (Note: <br />When snowpack exceeds 200 percent of normal February I to Febru- <br />ary 15, seeding will be suspended due to above-normal snowpack <br />criteria. ) <br />Observations of avalanche occurrences during the 1971-72 season indi- <br />cated that either the lO-day totalQ!:. the 24- hour maximum precipitation amount <br />was capable by itself of inducing avalanche occurrences. Consequently, after <br />the 1971-72 season, several changes were made in the avalanche criteria. One <br />of the primary changes was replacing the predetermined 24- hour period of 1100 <br />MST to 1100 MST with any consecutive 24- hour maximum precipitation forecast. <br />Following are the new criteria which reflect the changes that were made <br />prior to the 1972-73 season. These were in effect for the remainder of the <br />Proj ect: <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/or 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/or preceding <br />lO-day precipitation accumulation of 2. 50 inches or greater water <br />content. <br />4) Snowpack 151 percent of normal or above, 24-hour maximum forecast <br />precipitation of O. 7 inch or greater , and/or a preceding 10-day preci- <br />pitation accumulation of 1. 75 inches or greater water content. (Note: <br />When snowpack exceeds 200 percent of normal February I to Febru- <br />ary 15, seeding will be suspended due to above-normal snowpack <br />criteria. ) <br />A graph of the Wolf Creek Pass snowpack measurements for the five <br />operating seasons is presented in Figure 2- 5. <br />Requests for suspension of seeding operations over the five-year period <br />are listed in Table 2-2. For the five seasons, thirteen requests for suspension <br />were made (ten granted; three denied). <br /> <br />~ <br /> <br />:; <br /> <br />2-16 <br />