A climate version of the Regional Atmospheric Modeling System (RAMS) is used to simulate snow-related land-atmosphere interactions in the Great Plains and Rocky Mountain regions of the United States. The availability of observed snow-distribution products allow snow-water-equivalent distribution data to be assimilated directly into the RAMS simulations. By performing two kinds of model integrations, one with and one without assimilating the snow-distribution observations, the differences between the model runs are used to highlight model deficiencies and limitations and thus identify areas of possible improvement in the atmospheric model. The need to simulate subgrid snow distributions is identified and addressed by implementing a snow submodel that accounts for subgrid variations in air temperature and precipitation. This subgrid snow model is found to significantly improve the model's simulation of snow-related processes. ¿ 1999 American Geophysical Union