Warm season, convective precipitation over the high terrain in western Mexico is critical for regional water resources. Rainfall in this region, attributed to the North American Monsoon System, is responsible for comparatively large portions of the annual streamflow volume. Despite its great societal importance as a water resource, relatively little is known about the detailed spatial and temporal structure of the diurnal convective precipitation in the complex terrain of the Sierra Madre Occidental. This study presents findings from recent diagnostic and modeling work which documents the large sensitivity in modeled precipitation and runoff response to convective parameterization. Specifically, regional climate modeling results from three single season integrations exhibited dramatic and statistically significant differences in both the regional moisture flux and hydrological fields to three different convective parameterization schemes. While the differences between the simulations are, partially attributed to the large differences in the convective fraction of precipitation, definitive verification of the model estimates, in terms of the intensity, duration and frequency of precipitation events, is inhibited by deficiencies in the existing observing network. Shortcomings, of existing precipitation monitoring network will be detailed as will the plans for an upgraded ground-based network. The new network is due to be implemented in two phases over the next two years and will provide enhanced temporal and topographic resolution of the precipitation field over western Mexico in support of the upcoming North American Monsoon Experiment.