####018003262#### AGUS74 KWCO 151526 HMDNWC National Hydrologic Discussion - EXPERIMENTAL NWS National Water Center - Tuscaloosa AL 1015 AM CDT FRI MAR 15 2024 .Synopsis... Isolated flash, urban, and minor to isolated moderate river flooding possible in Texas... Ongoing river flooding in Northeast Texas, Lower Mississippi Valley, and Alabama and Middle Mississippi Valley into the Ohio Valley... .Discussion... .Texas... Multiple rounds of moderate to heavy rainfall (2 - 4" WPC 3-day totals) will impact the eastern half of Texas starting late on day 2 (Sat) and continue through the weekend, bringing the potential for isolated flash and urban flooding impacts to the region. Minor to isolated moderate river flooding may be possible as well. Antecedent conditions are generally on the dry side, particularly in South TX and TX Coast due to well below normal rainfall over the past 14 days (RFC QPE). This should help mitigate widespread impacts and thus limiting much of the impacts to urban and typical poor drainage areas. Recent runs of the National Water Model (NWM) Medium Range Forecast (MRF) have only shown very isolated responses on streams and rivers which may be driven in part by the drier conditions however, there will be the potential for repeated rounds of locally heavy rainfall through the weekend which may lead to increasing soil moisture. This may be better reflected by the NWM Short Range Forecast (SRF) tomorrow afternoon as the event draws closer. Southern Region QPF Ensembles still show a chance for new/renewed river rises and minor to isolated moderate river flooding across TX from Hill Country to the coast and East TX. .Northeast Texas, Lower Mississippi Valley, and Alabama... Lingering river rises and highwater flows will continue following recent rainfall of 2 - 3" and locally higher amounts greater than 5" overnight and this morning. The NWM High Flow Magnitude Analysis, which reflects the current stream and river conditions following the heavy rainfall, shows isolated areas of lower AEPs suggesting ongoing highwater flows across the area. Isolated minor river flooding is already ongoing and forecast with smaller rivers cresting today and some of the larger rivers cresting over the next couple days or remaining in flood through the weekend. Redevelopment of rainfall across southern MS/AL in the afternoon may lead to additional localized flash, urban, and small stream flooding impacts. The NWM SRF continues to signal the potential for isolated rapid-onset flooding (ROF) with isolated higher probabilities for ROF (25 - 50%). Additionally, the SRF High Flow Magnitude Forecast shows isolated areas of lower AEPs suggesting confidence in localized significant rises. .Middle Mississippi Valley into the Ohio Valley... Due to recent rainfall across the region, widespread 1 - 2" with local amounts near 4" (MRMS QPE), minor river flooding is ongoing and forecast through the weekend into early next week. However, a few of the slower-responding rivers will remain elevated beyond the forecast period. //Smith/Zawislak $$