A successful mesoscale (grid increment=1-3 km) real-time, four-dimensional data assimilation (RT-FDDA) and short-term forecasting system was introduced by Cram et al. (2001, 14th NWP Conf.). Since then, many refinements and improvements have been added to the system. The system has been deployed to a number of test ranges of the U.S. Army Test and Evaluation Command (ATEC), including the Dugway Proving Ground in Utah, the White Sands Missile Range in New Mexico, the Yuma Proving Ground in Arizona and the Cold Region Test Center in Alaska. By properly adapting the model to the range environments, and by incorporating observations from various sources (including the special observations from the range mesonets), the system has shown superior skill in providing high-quality weather analyses and forecasts to support the routine tests at these ranges. Recently, the system has been enhanced by incorporating observations from the hourly NPN-profiler network, from Boundary-Layer Profiler networks and from ACARS. A strict and reliable Quality-Controlled (QC) scheme was built, based on the fast-updated, accurate, 1 - 3 hour forecasts of the system. In addition, the land-surface physics was upgraded to the OSL Land-Surface Model (LSM) from the previous simple slab-soil model. In this paper, the development and overall performance of the RTFDDA system, and specific aspects of the performance at each range, will be assessed through long-term statistics and case-study analyses. Significant positive impacts of the 1) newly added profiler and ACARS observations, 2) the effective QC scheme, and 3) the OSL/LSM physics on the analyses and forecasts of the system were found through a month-long parallel test.