Henderson Mill is located in the high elevations of the Colorado Rockies where the risk to hydrologic infrastructure may be associated with rain-on-snow events. In this study, MetStat® conducted a storm search for extreme storms to identify rainfall-dominated precipitation patterns during the Spring runoff season for application in a maximum precipitation study. Using traditional methods for developing probable maximum precipitation, storm analyses were performed, which included: the generation of storm temporal and spatial patterns; development of depth-area-duration (DAD) curves; storm maximization and transposition; elevation adjustments; and, calculation of a maximum precipitation value. Storm maximization and transposition requires an assessment of the source and magnitude of moisture inflow into the storm using the HYSPLIT back-trajectory model (see figure). In addition, areal reduction factors were applied to reduce the point maximum precipitation to the area size of the watershed. The output from the springtime maximum precipitation study will be implemented in a hydrologic model with a snowmelt runoff climatology information to generate a rain-on-snow hydrograph for assessment of risk in the Henderson Mill drainage. This project was a collaborative effort between MetStat® and Atmospheric Science Consultants, both members of the Extreme Precipitation Group.