Estimation of 30 year average annual precipitation for SNOTEL sites in Idaho

The Soil Conservation Service (SCS) operates and maintains a network of 69 automated SNOTEL (SNOw TELemetry) sites in Idaho. Most have a continuous daily precipitation data record from 1982. 1961-1990 average annual precipitation (AAP) was estimated for 65 of the sites having more than five years of data using simple linear regression. Water year annual precipitation for the available years was compared to nearby national Weather Service (NWS) stations. Up to 14 NWS stations were analyzed for each SNOTEL site. The three highest correlating NWS sites for each SNOTEL site were selected and the 1961-1990 AAP at the NWS sites was used to estimate three 30 year AAP values for each SNOTEL site from the regression equations. The final 1961-1990 AAP for the SNOTEL sites was the mean calculated from the three individual values. High correlations were consistently obtained between SNOTEL and NWS annual precipitation.