Flight delays are now a major problem in the U.S. National Airspace System. A significant fraction of these delays are caused by reductions in en route capacity due to severe convective weather. The Corridor Integrated Weather System (CIWS) is a fully automated weather analysis and forecasting system designed to support the development and execution of convective weather impact mitigation plans for congested en route airspace. The CIWS combines data from dozens of weather radars with satellite data, surface observations, and numerical weather models to dramatically improve the accuracy and timeliness of the storm severity information and to provide state-of-the-art, accurate, automated, high-resolution, animated three-dimensional forecasts of storms (including explicit detection of storm growth and decay). Real-time observations of the Federal Aviation Administration (FAA) decision making process during convective weather at Air Route Traffic Control Centers in the Midwest and Northeast have shown that the CIWS enables the FAA users to achieve more efficient tactical use of the airspace, reduce traffic manager workload, and significantly reduce delays. A real-time data-fusion architecture to assist in national deployment of CIWS is under development, and the CIWS products are being used in integrated air traffic management decision support systems.