A prototype real-time four-dimensional data assimilation (RT-FDDA) system was implemented at Dugway Proving Ground (DPG) in mid 2000 for operational use in supporting field tests. The DPG RT-FDDA system uses observation nudging (Newtonian relaxation) with the Penn State/National Center for Atmospheric Research (NCAR) Mesoscale Model Version 5 (MM5) with three nested computational domains (grid spacing of 30, 10, and 3.3 km) to analyze all available meteorological measurements and provide short-term forecasts. Because the majority of DPG field tests include the dissemination and sampling of gaseous or aerosol tracers near the surface, successful test conduct requires an accurate knowledge of the spatial and temporal variations of the wind field in the planetary boundary layer (PBL). This paper will summarize the DPG RT-FDDA system's output, discuss verification of it's PBL wind forecasts, and illustrate how RT-FDDA output has been linked with a Gaussian puff dispersion model to provide short-term forecasts of dissemination test results to assist in go/no-go test decisions.