Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 432 AM EDT Sat May 17 2025 Day 3 Valid 12Z Mon May 19 2025 - 12Z Tue May 20 2025 ...THERE IS SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF THE CENTRAL PLAINS INTO THE LOWER AND MIDDLE MISSISSIPPI VALLEY... Another day of widespread heavy rainfall expected across the middle portion of the country on Monday as the longwave trough and embedded shortwave energy slowly moves eastward. It will likely be an active day/night with a broad region where flash flooding will be possible. A Slight risk stretches from northeast TX northward into southern IA. The northern extent of the Slight risk will be close to or just north of the stationary front extending east of the central Plains low pressure. Strong forcing overrunning this boundary will likely result in an expansive area of convection, with some training/backbuilding possible. The southern portion of the Slight risk is driven by initial dryline convective development, likely enhanced by the eventual eastward acceleration of the cold front south of the low. The convergence from the dryline, cold front and lifting warm front will all aid in convective development. The general stagnant nature of the frontal feature through much of the day (both the warm/stationary front and dryline) support a training/backbuilding convective threat. Exactly where the focus of highest QPF ends up remains a bit of a question, but generally anywhere within the Slight risk is in play. There is some signal that the axis from northeast TX into southern MO could actually see the most intense rates and greatest flash flood potential, with both the 00z CMC and AIFS highlighting this corridor. However ingredients will also be quite favorable farther north into MO and southern IA as well (pending exact frontal positioning) and thus both of these areas could end up seeing training/backbuilding at some point Monday and/or Monday night. Some of these areas will also likely see heavy rain on day 2 as well, and so hydrologic conditions could be more sensitive by this day 3 time frame. Thus do consider just about all of the Slight risk as a higher end Slight at this time, and think areas of flash flooding are likely. It seems possible (maybe even probable) that an embedded MDT risk will eventually be needed somewhere within the broad Slight risk area. However uncertainty in both the convective details and hydrologic conditions (pending what rainfall happens on day 1 and 2) leads to low confidence in any MDT risk location at this time. Thus we will hold with a higher end Slight and continue to monitor trends. Chenard Day 3 threat area: www.wpc.ncep.noaa.gov/qpf/99epoints.txt