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<br />19 <br /> <br />temperature, and even the magnitude of the snowpack water content itself <br />affec.t the ratio. Further error was introduced by the fact that most <br />precipitation stations were not precisely co-located with the nearby <br />snow course. Insufficient data were available to justify performing <br />multiple regression analysis using these and other variables. Instead, <br />subjective modifications were permitted to improve the estimates of <br />winter season precipitation. In many areas excellent improvements on <br />the first approximation could be made by using other known climatic <br />information for a given site. For example, the regression equation <br />applied to the Blue Mesa snow course predicts 11.21 inches of October- <br />April precipitation. Because this area is known for being unusually <br />cold for its elevation (resulting in less reduction of the April 1 <br />snowpack by melting than at other sites) and because April precipitation <br />is normally light in that area (less than 1 inch), the estimate was <br />subjectively lowered to 10.00 inches. Please note that in the appendix <br />all October-April precipitation estimates that were subjectively <br />modified from their regression-determined values are appropriately <br />noted. <br />The second step in determining estimates of annual average <br />precipitation at snow courses was to estimate summer (May-September) <br />precipitation. Summer season estimates were based on available measured <br />data in the vicinity of snow courses and on the 1931-1960 map analysis <br />of May-September average precipitation. The distribution of summer <br />precipitation in Colorado is much more uniform than winter <br />precipitation. With few exceptions most of the mountainous areas of <br />Colorado receive from 8 to 14 inches of May-September precipitation, <br />