At the beginning of winter, basin averages of seasonal precipitation and snowpack were below average. By April 1, snowpacks reached above average levels. During May, the anomalous weather patterns began. Precipitation during May was over 300 percent of average. Temperatures were cooler than normal which delayed the onset of runoff. June precipitation was over 150 percent of average. Temperatures continued on a below normal track.
Runoff patterns were greatly altered by the anomalous conditions. Large-scale runoff did not begin until mid-May with a great percentage of the spring runoff occurring in June. Runoff was heavier than expected partly due to much above normal precipitation during the runoff period. Generally, the most probable forecasts were lower than observed values. Characteristic of this extreme year, the observed values for most forecast points within the Upper Colorado mainstem fell outside the confidence intervals. That is, observed flows surpassed the 10% exceedance probability forecasts.
