On August 21, 2021, a widespread extreme rainfall event impacted the Tennessee Valley along the lower Duck River watershed. The rainfall shattered the Tennessee state 24-hour rainfall record, with more than 17 inches recorded at McEwen, TN. The resulting flood was catastrophic, causing millions of dollars in damages, and tragically, the loss of 22 lives, primarily in and around Waverly, TN. The nature of the event, in its intensity, duration, and coverage, was extraordinary and demonstrated the value of the Tennessee Valley Authority’s long standing extreme hydrology program. Following the event, TVA River Management and TVA Dam Safety gathered operational experience and rainfall data to support executive review of TVA’s preparedness for extreme hydrologic events. This presentation will provide an overview of the Waverly storm event, TVA’s estimation of the storm’s probability, and lessons learned from the operational forecasting experience. The discussion will also cover actions taken by TVA to understand potential impacts of a similar event in the future, and to better prepare TVA personnel responsible for managing TVA’s hydropower and non-hydropower dam assets.