The Rapid Update Cycle analysis/model system at a 20-km horizontal resolution (RUC20) provides short-range numerical weather guidance for general forecasting, as well as for the special short-term needs of aviation and severe-weather forecasting. This data set consists of 60 meteorological and soil parameters at 50 computational levels. Data are available from 1 October 2002 to 1 October 2003. ... RUC20 is a further development on the RUC40 model that produced output at a 40 km horizontal resolution. The NASA Cold Land Processes Experiment (CLPX) is a multi-sensor, multi-scale experiment that focuses on extending a local-scale understanding of water fluxes, storage, and transformations to regional and global scales. Within a framework of nested study areas in the central Rocky Mountains of the western United States, ranging from 1-ha to 160,000 km2, intensive ground, airborne, and spaceborne observations are collected. Data collection focuses on two seasons: mid-winter, when conditions are generally frozen and dry, and early spring, a transitional period when both frozen and thawed, dry and wet conditions are widespread.