Challenges with Impact-Based Decision Support Services for the Mississippi River Flood of 2019

In 2019, the Mississippi River experienced the second highest flood crest on record at St. Louis, staying above major flood stage for more than a month. Since 2013, the river has crested above major flood stage four times at St. Louis, which is unprecedented given the fact the river has only recorded ten major flood crests since gauge readings began in 1861. Impact-based decision support services (IDSS) and associated messaging for this flood began early in 2019, as climate outlooks predicted above normal precipitation for most of the spring and antecedent conditions favored significant flooding. With such long lead times, state and local governments were able to prepare for major flooding, but new challenges with messaging and IDSS became apparent during the spring when forecasts favored a longer duration flood that would continue into the summer of 2019. The Mississippi River remained above flood stage at St. Louis for 126 days, which stretched local government resources very thin and added stress to the levee system that protected vulnerable populations and infrastructure. This presentation will examine the unique challenges to IDSS that the 2019 flood posed and how the NWS in St. Louis managed these challenges.