The historic flooding of the Lower Mississippi and Atchafalaya Rivers during the spring and early summer of 2011 was the result of significant snow-melt in March and April on the upper reaches of the Mississippi River; heavy rainfalls in the Ohio River basin in March through May; and heavy rainfalls that impacted the Mid-Mississippi Valley (mainly from Oklahoma, Arkansas and Missouri eastward to Kentucky) in April and May. Rainfalls as much as 400-600% of normal were reported in some areas. This historic flood was very prolonged and continued to impact portions of the Mississippi and Atchafalaya Rivers well into June.

The NWS Lower Mississippi River Forecast Center routinely issues forecasts for points along the Mississippi River for the next five days. The River Forecast Center also issues 30-day guidance known as Extended Streamflow Prediction once a week, but those data are primarily used in automated, scripted processes by large NWS customers such as the U.S. Army Corps of Engineers. However, in a long duration flood of the magnitude of that of the spring and early summer of 2011, the need for long-range crest forecast information became critical to mitigation efforts in the path of the flood. Prior to the 2011 Mississippi flooding event, the Extended Streamflow Prediction data had not been made available on NWS Web pages in a format appropriate for the wider audience that suddenly needed the information.

When it became apparent that presenting the long-term river forecast information, together with a variety of other NWS products, in a user-friendly manner would be very important to the emergency management community and the general public living along the river, a small team was formed to rapidly determine the requirements for the final product. This poster will include a description of the software and technology used to collect, format and display the data, indicate how the data were used during the event, and highlight customer feedback that will help shape the future of NWS decision support Web pages.