The Areal Mean Basin Estimated Rainfall (AMBER) algorithm was installed at the Tucson WFO to assist forecasters in issuing timely flash flood warnings. AMBER uses the 1 degree x 1 km Digital Hybrid Reflectivity Scan from the WSR-88D to estimate the average basin rainfall (ABR) for six periods and the basin rate of accumulation. The algorithm also compares the ABR to flash flood guidance values that alerts the forecaster to basins near or exceeding flash flood guidance. Forecasters can then examine the alerting status of the particular basin and decide if a flash flood warning is necessary. The results of AMBERís performance and its impact on the flash flood warning verification program at the NWS Tucson WFO are presented.