Two commonly used measures of the convective 'cap' are compared for the purpose of forecasting convection. Using digital MM5 grid point data, values of Lid Strength Index and Convective Inhibition are compared to cloud-to-ground lightning strikes, which are equated with 'convection' in this study. There are three major conclusions: 1) For many purposes, the Lid Strength Index verifies as the superior 'cap' index. 2) Threshold values of Convective Inhibition much lower than the traditional values of -50 or -100 J/Kg should be considered, especially in the winter. 3) The skill and utility of cap indices varies with season, time of day, and region.