####018003880#### AGUS74 KWCO 241507 HMDNWC National Hydrologic Discussion - EXPERIMENTAL NWS National Water Center - Tuscaloosa AL 1015 AM CDT SUN MAR 24 2024 .Synopsis... Localized flooding potential for East Texas...Isolated river and small stream flooding impacts possible in the Lower Mississippi Valley... Ongoing river flooding with a return of rainfall early and again late week in the Southeast... Urban and small stream flooding impacts possible for Puerto Rico and USVI...Ongoing and forecast coastal flooding impacts early this week for the Coastal Mid-Atlantic and Northeast... .Discussion... .East Texas... Moderate rainfall will bring the potential for localized flooding impacts later today to streams that have already seen recent rainfall. Minor flooding is ongoing or forecast for the region and any new rainfall could elicit new and/or renewed flooding impacts. .Lower Mississippi Valley... Moderate to heavy rainfall will return to the region on day 2 (Mon) and while minor river flooding is ongoing due to multiple rounds of rainfall over the past 7 days, any new rainfall may cause new and renewed rises along with stalled recessions. Top soils are wet (60 - 70%, 0 - 10 cm, NASA SPoRT) and streamflows are running normal to much above normal indicating there is storage capacity available however, any locally heavy rainfall could lead to runoff and out-of-bank rises on small streams. The National Water Model (NWM) Medium Range Forecast (MRF) rapid-onset flooding probabilities are signaling probabilities generally around 25% and associated annual-exceedance probabilities (AEPs) greater than 50% with isolated signals less than 20% across portions of AR, northern LA, and much of MS on days 2 and 3 (Mon - Tue). This suggests that while widespread river flooding is not likely, localized flooding is probable. .Southeast... Locally heavy rainfall returns to the Southeast late on day 2 (Mon), bringing the potential for isolated flash, urban, and small stream flooding impacts, along with river rises across AL. This system will continue to move east into GA, FL and SC on day 3 - 4 (Tue - Wed). Streamflows are generally normal to above normal following recent rainfall. Despite the extended range, models continue to agree on the placement of the rainfall, giving confidence in the location for potential impacts. Both the GFS- and NBM-forced NWM MRF show stream responses from central AL through central GA onto the coast. Given these factors, the region will need to be closely monitored in the coming days. .Puerto Rico and USVI... Urban and small stream flooding impacts will be possible on Monday for Puerto Rico due to a passing cold front. As that front continues east, the U.S. Virgin Islands will see the same elevated concerns for flooding later in the evening. .Coastal Mid-Atlantic and Northeast... As past rainfall (last 24 hours), of 1 - 3", routes downstream, minor to moderate river flooding will continue across portions of northern NJ, CT, RI, and southern MA, cresting early this week before receding thereafter. Additionally, RFC forecasts continue to show widespread minor to moderate coastal flooding impacts starting from northern NC northwards to MA due to a combination of high tides and onshore flow. Later this week, additional rainfall may impact the region and elicit new flooding impacts, and the NWM MRF is indicating small stream responses across portions of the Coastal Mid-Atlantic into southern New England on days 5 - 6 (Fri - Sat). However, given run-to-run inconsistencies between models, uncertainty remains in the exact location and magnitude of impacts. //Kirkpatrick/Pritchard $$