Electrical Power for Valdez and the Copper River Basin-1981

AVERAGE MONTHLY TEMPERATURES (OF),1anFebMarAprMayJunJulAugSepOctNovDecValdez1 7.822.42 i). 835.1)43.851.253.352.046.537.526. 119.5Cordova23.026.729.236.043.750.453.453.048.039.630.624.6The Valdez data are recorded by the National Weather Service at anelevation of 87 feet mean sea level (MSL). The Cordova data are recordedby the Ferleral Aviation Administration at an elevation of 41 feet MSL.The temperatures range between 42° F and 60° F during the summer andbetween 11° F and 43° F during the winter for Valdez with the extremesbeing _28 0 F and 87° F. The temperatures range between 44 D F and 61° Fduring the summer and between 21° F and 39° F during the winter forCordova with the extremes being -23° F and 86° F.80th locations average a growing season of about 4 months. Normally,the first freeze occurs early in September and the last freeze occurs inmid-May.Summertime temperature gradients follow the traditional pattern ofdecreasina temperatures with increasing altitude. During periods ofextreme winter cold, how~ver, a strong temperature inversion may exist inthe lower layers of the atmosphere as a result of radiation cooling andcold air drainage for the surrounding mountains. Under these conditions,the temperature gradient will be reversed.Precipitation:Precipitation over the basin varies from moderate amounts in the lowelevations to heavy in the mountains, to moderate amounts again in theKlutina and Tonsina drainages. The orographic effect of the ChugachMountains insures heavy precipitation in the upper elevations of thebasin and lower amounts in the lower basin. Storms are generally lightin intensity, with few convective-type storms of cloudburst magnitude.The only climatological stations in the study area with reasonablycomplete precipitation data are located in Valdez and Cordova. Averagemonthly precipitation for these communities is presented below.A-3