Joint NOAA/NWS/USGS Prototype Debris Flow Warning System for Recently Burned Areas in Southern California

Evaluation of the inaugural year of operation of the prototype debris-flow warning system in Southern California indicates that: * Watches provide valuable information that allows for adequate lead time for preparation, road closures, and posting of emergency vehicles in hazardous areas. * Precipitation measurements from the Automated Local Evaluation in Real Time (ALERT) raingauge network, and forecaster experience, are necessary to augment both forecasting models and operational radar precipitation data. * Small, portable radars can augment observations from the fixed-site operational radar network with highly accurate, finer-scale estimates of precipitation. * Rainfall thresholds provide a very conservative estimate of hazardous rainfall conditions throughout an entire burned area.