Mountain thunderstorms often originate in preferred regions of the topography, as shown qualitatively by pilot reports and more quantitatively by meteorological radar, satellite, and lightning detector studies. To further investigate the phenomenon of mountain thunderstorm initiation, we used time sequences of GOES imagery to locate storms and to trace them back to their points of origin. Using three summers of data from days which started out clear, we backtracked over 600 storms in the mountains of Colorado and northern New Mexico. We plotted the origin points on a terrain map and drew contours of initiation frequency to identify regions with a high likelihood of producing thunderstorms. We found that initiation sites tended to cluster into identifiable geographical locations or “genesis zones”, consistent with findings based on the other data sources. When cloud propagation effects were taken into account, the locations of these genesis zones were also consistent with the locations of clusteri... Abstract Mountain thunderstorms often originate in preferred regions of the topography, as shown qualitatively by pilot reports and more quantitatively by meteorological radar, satellite, and lightning detector studies. To further investigate the phenomenon of mountain thunderstorm initiation, we used time sequences of GOES imagery to locate storms and to trace them back to their points of origin. Using three summers of data from days which started out clear, we backtracked over 600 storms in the mountains of Colorado and northern New Mexico. We plotted the origin points on a terrain map and drew contours of initiation frequency to identify regions with a high likelihood of producing thunderstorms. We found that initiation sites tended to cluster into identifiable geographical locations or “genesis zones”, consistent with findings based on the other data sources. When cloud propagation effects were taken into account, the locations of these genesis zones were also consistent with the locations of clusteri...