The potential economic and safety benefits of improved short-term weather predictions are well known. Due to the modernization of the national weather observing system, meteorologist will have access to data of much better spatial and temporal resolution than previously possible on a day to day basis. This improvement in the operational weather system provides opportunities for enhanced research in the area of mesoscale meteorology. Mesoscale meteorological processes generally control the timing, location and severity of most life threatening and economically disruptive weather such as flash floods, heavy snowfalls, tornadoes, etc. The opportunities for fundamental improvements in short term forecasts (up to two days) has caused several agencies within the US government to plan a major interagency research program known as the US Weather Research Program (USWRP). The USWRP consists of several components including a series of intensive field observational studies. The first of these, know as the Stormscale Operational and Research Meteorology-Fronts Experiment, Systems Test (STORM-FEST), has three closely related objectives: focussed investigation of the structure and evolution of wintertime fronts and associated mesoscale phenomena with emphasis on precipitation and severe wintertime weather (e.g. severe icing conditions); a research assessment of the new operational and research meteorological instrumentation facilities and composite observational networks; a study to begin to understand mesoscale prediction capabilities and limitations in active frontal regions. The Principal Investigator will use a wide variety of research and operational data, including data from the next generation of operational instruments, to study frontal mesoscale structures. The data will come from the STORM-FEST and a previously completed experiment which studied east coast winter storms, know as the Genesis of Atlantic Lows Experiment (GALE). The principal objectives of the research are to: document the structure of precipitation in winter cyclones; to determine the mechanisms responsible for the organization of significant mesoscale precipitation phenomena; to improve the forecasting of heavy precipitation in winter cyclones.