Climate Context of the 2018–19 Mississippi River and Tributaries Floods

The 2018-2019 flood season produced an astounding series of flood events throughout the Mississippi River system and its tributaries. The expansive area of flooding in the Mississippi River system is not common. The flooding impacted all the major river systems from the Ohio, upper Mississippi, Missouri and Arkansas Rivers to the middle and lower Mississippi River. The National Oceanic and Atmospheric Administration (NOAA)/National Weather Service (NWS) issued accurate spring flood outlooks highlighting the expansive flood risk both in areal extent and coverage.

Summarizing the weather events from this season that drove the flooding in order to put them in the context of past weather events shows interesting comparisons and contrasts. While there were some individual record events, taken individually at a watershed scale, many of the events cannot be represented as extremes of the climate record. However, as the events are aggregated over larger areas and longer periods, they do become outliers in the climate record. This study examines the climate context of the 2018-2019 weather events across the area of responsibility of five NWS River Forecast Centers (RFCs) at different scales and durations. We also compare the 2018-2019 antecedent conditions and flood events with the historically largest flood events as a gage of the risk for more extreme events, and explore any analogs from some of the more clearly defined climate signals. This information can inform decisions that water resources managers might make in considering the effects of a non-stationary climate on water resource projects.