Wind speed and C2n measurements made with the Poker Flat, Alaska, MST radar are used to study the development of clear air turbulence (CAT) near the tropopause. Arguments and observations indicating that C2n is proportional to the intensity of turbulence are presented. The relationship between wind shear and turbulence is examined by using time-lagged cross correlations between vertical wind shear and log C2n time series. From analysis of data taken with spatial resolutions of 2200 m and 750 m, it is found that the correlation improves as the time and spatial resolutions of the measurements improve. The implications for forecasting CAT are discussed, based on the correlation results and a comparison of radar data with National Weather Service CAT forecasts.