FLASH: From Radar Observations to Operational Flash Flood Forecasting

The advent of weather radar revolutionized the discipline of hydrology advancing it from basin-wide or basin-averaged thinking to spatially variable fields of rainfall and associated process understanding and representation. The Flooded Locations And Simulated Hydrographs (FLASH) system runs on the back end of the NEXRAD-based Multi-Radar, Multi-Sensor (MRMS) system to provide context for the quantitative precipitation estimates, produced on a 1-km pixel grid with updates every 2 min across the entire US and outer territories. FLASH ingests these QPEs and 1) compares them to static rainfall climatologies to yield average recurrence intervals (ARIs), 2) compares them to dynamic rainfall thresholds using the flash flood guidance methodology, and 3) forces a suite of streamlined hydrologic models operating at flash flood scale. This presentation will give an overview of the FLASH system leading up to its transition to operations in the National Weather Service, highlighting several use cases. Perspectives will be provided on research to further increase forecast lead time, to highlight specific impacts, to generate probabilistic outputs, and to incorporate additional physical processes.