Temperature and wind forecasts from the Penn State/NCAR Mesoscale Model version 5 (MM5) in the U.S. Army's Four-dimensional Weather (4DWX) system are validated with surface and upper-air measurements over northern Utah. Surface measurements include observations from Dugway Proving Ground's network of automated surface stations, MesoWest, and other observational networks. The period of study extends over 82 days beginning in February, 2002, when the high-resolution inner domains of MM5 were centered over the Wasatch Mountains and 2002 Winter Olympic venues. Temporal variability statistics with respect to surface characteristics, such as snow cover, and synoptic systems are presented. Results from four-dimensional data assimilation (FDDA) analyses are compared with the MM5 forecasts and are used to describe mesoscale circulation features in the mountain terrain.