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<br />snow coming over the top from the west) but do not necessarily receive higher amounts from <br /> <br />indiVidual storms. Most Front Range snow storms have maximum precipitation at mid elevations. <br /> <br />In summer the large convective rain storms decrease in precipitation at higher elevations. But the <br /> <br />. higher elevations can receive more total precipitation due to a larger number of days with <br /> <br />precipitation. <br /> <br />3.3 Large Daily Precipitation <br />The other characteristic of precipitation important to any discussion of variability is the <br /> <br />role oflarger amounts of daily precipitation. Figure 4 shows the percent of annual precipitation <br /> <br />as a function of the percent of daily events of precipitation for the Northern Front Range of <br /> <br />Colorado and for the State as a whole from Cowie et al. (1986). The graph shows that 50% of <br /> <br />the annual precipitation comes from about 18% of the days with largest amounts of precipitation. <br /> <br />About 50% of the days contribute nearly 80% of the precipitation. Since most of the precipitation <br /> <br />come from a relatively small number of days with larger amounts of precipitation, it would follow <br /> <br />that the large daily events would dominate the variation of precipitation from year to year. The <br /> <br />study of daily precipitation in Colorado by Cowie et al. (1986) for the period 1951-1980 showed <br /> <br />that the larger daily events which produced just 24% of the annual precipitation produced 59% of <br /> <br /> <br />the change in annual precipitation from the 10 driest years to the 10 wettest years. This leads to <br /> <br />the conclusion that the addition or subtraction of just a few large storms is the primary difference <br /> <br />between dry and wet years. The change in the total number of days with precipitation is a <br /> <br />secondary contributor. The study reported here used monthly data, so no information is given <br /> <br />about the cause of year- to-year variations. <br /> <br />10 <br />