####018004186#### AGUS74 KWCO 141513 HMDNWC National Hydrologic Discussion - EXPERIMENTAL NWS National Water Center - Tuscaloosa AL 1015 AM CDT THU MAR 14 2024 .Synopsis... Flooding impacts are possible in Northeast Texas, Oklahoma, and Lower Mississippi Valley, East Texas into the Southeast, and Missouri, Illinois, and Indiana... .Discussion... .Northeast Texas, Oklahoma, and Lower Mississippi Valley... Widespread moderate to locally heavy rainfall (1 - 3" WPC) is forecast to develop in eastern OK this afternoon and expand into AR, LA, MS, western TN and even extreme southern MO through the afternoon and evening. This will bring the potential for isolated flash and urban flooding impacts. Antecedent conditions are generally near normal with near-surface (0 - 10 cm) relative soil moisture ranging between 50 - 60% (NASA SPoRT). Streamflows are generally near normal historically however, they are below normal for this time of year. This suggests that soils and channels should be able to handle much of the rainfall at least initially. In the event of repeated rounds/training or enhanced rainfall rates, the soil infiltration capacity and smaller stream channel capacity could be overwhelmed particularly in the areas of steep terrain producing isolated flash and urban flooding impacts including new and renewed river rises. The National Water Model (NWM) Short Range Forecast (SRF) is starting to capture the rainfall for this event and beginning to signal isolated instances of rapid-onset flooding across eastern OK and AR with high water arrival times generally late this afternoon and evening. Additionally, there have been isolated signals on recent runs of the SRF for lower Annual Exceedance Probabilities (AEPs) across the Ouachitas in central AR suggesting significant out-of-bank flows. These signals may expand as the event draws closer. .East Texas into the Southeast... Multiple rounds of moderate to heavy rainfall (1 - 3" WPC 5-day totals) are forecast across East TX into the Southeast starting on day 2 (Fri) and continuing through the weekend. Antecedent conditions are wetter across MS and AL due to recent heavy rainfall last weekend. Models remain somewhat variable as to where the heaviest rainfall sets up but overall, models have trended further south and west and lower in total QPF with the bulk of the rainfall forecast across east TX and southern LA. The NWM Medium Range Forecast (MRF) has also trended downward in the magnitude of the signals with the majority of the highwater signals placed across north MS/AL along with embedded areas of lower AEPs for streamflows in northern MS suggesting a more isolated nature of significant flows however, with the current disagreement among the models, uncertainty remains on if or where heavy rainfall sets up. River ensemble forecasts generally follow a similar downward trend suggesting only modest renewed rises across the southeast (MMEFS), but a better chance for new/renewed river rises and minor river flooding across East TX (SR QPF Ensembles). Minor to moderate river flooding is ongoing across MS, AL, GA, and SC due to recent rainfall, and will likely continue through this week for many locations. Most locations have already crested however, many of the forecast locations on larger rivers closer to the coasts will continue to rise through the week. .Missouri, Illinois, and Indiana... Moderate rainfall (1 - 2", WPC) today may bring the potential for rises on area streams and rivers, with moderate flooding forecast today along Crooked River (MO) and Wakenda Creek (MO) and minor river flooding forecast this weekend along the Illinois (IL) and Wabash (IN) rivers. Top-layer soils are near normal (45 - 55% RSM, NASA SPoRT) and streamflows are generally near normal to slightly above normal historically (USGS), which should mitigate any widespread flooding due to ample soil infiltration and channel capacity that exists. //Smith/Zawislak $$