The U.S. aviation system makes extensive use of national operational Doppler weather radar networks. These are critical for the detection and forecasting of thunderstorms and other hazardous weather phenomena, and they provide dense, continuously updated measurements of precipitation and wind fields as inputs to high-resolution numerical weather prediction models. This article describes recent Lincoln Laboratory activities that significantly enhance the operational effectiveness of the nation's Doppler weather radar networks. An open radar controller and digital signal processor has been developed for the Terminal Doppler Weather Radar (TDWR), which provides safety-critical low-altitude wind-shear warnings at large airports. This processor utilizes a small computer cluster architecture and standards-based software to realize high throughput and expansion capability. Innovative signal processing algorithms enabled by the new processor significantly improve the quality of the precipitation and wind measurements provided by TDWR. In a parallel effort, the Laboratory is working with engineers in the National Weather Service to augment the national NEXRAD Doppler weather radar network's algorithm suite. Laboratory staff develop and test enhancements directed at the aviation weather problem. Then they provide plug-and-play software to the NEXRAD second-level engineering support organization. This effort has substantially improved the operational value of NEXRAD data for the aviation system. Finally, we discuss nascent efforts to define a future multifunction radar network using an active-array architecture, which could realize the capabilities of today's multiple weather and air traffic control radar networks.