####018003734#### AGUS74 KWCO 071515 HMDNWC National Hydrologic Discussion - EXPERIMENTAL NWS National Water Center - Tuscaloosa AL 1015 AM CDT TUE MAY 7 2024 .Synopsis... Considerable flooding impacts continue in portions of East Texas... Isolated flooding impacts possible through Wednesday in Central and Eastern Montana... Isolated flooding impacts possible across the Middle Mississippi, Lower Ohio, and Tennessee Valleys, Puerto Rico and the USVI, and Alaska... .Discussion... .East Texas... Considerable river impacts are ongoing and will continue through much of this week across portions of southeast Texas. Major river flooding will continue this week along the Neches and Trinity rivers, with scattered moderate river flooding impacts throughout the region. Rivers should be able to recede unimpeded as QPF on any given day is expected to be less than 1" and the heaviest 7 day total is expected to be over the ARKLATEX (1 - 2", WPC). .Central and Eastern Montana... Periods of rain through day 2 (Wed) are expected across the region with forecasted small stream rises and potentially isolated minor to moderate river flooding on the Milk River. Isolated flash flooding cannot be ruled out either. The National Water Model (NWM) Short Range Forecast (SRF) does indicate a localized potential for rapid-onset flooding (ROF) with some areas, east of Billings, having probabilities greater than 50%. Additionally, associated annual exceedance probabilities (AEPs) are generally near the highwater threshold, with very isolated values around 10% near Billings as well. This suggests that though some small streams may see some significant flows, most streams should remain within banks. .Middle Mississippi, Lower Ohio, and Tennessee Valleys into the Southeast... Rainfall shifts east across the Middle Mississippi, Lower Ohio River, and TN Valleys through day 2 (Wed) where isolated small stream and flash flooding will be possible. On day 3 (Thu), this system will continue into the Southeast where 1 - 2" of precipitation is forecast (WPC). Soils in areas across the Middle Mississippi, Lower Ohio and TN Valleys are generally between 55 - 75% (0 - 10cm RSM, NASA SPoRT) suggesting there is some infiltration available over the region and most basins should be able to handle the large majority of the expected rainfall (1 - 3"). The NWM Medium Range Forecast (MRF) is signaling ROF probabilities generally between 25 - 50% and AEPs near its high water threshold. However, repeated rounds of storms, especially across western KY into TN, may increase the flooding potential thus limiting infiltration capacity resulting in isolated small stream and flash flooding impacts. .Puerto Rico and the USVI... Persistent rainfall through at least today will continue to provide a threat of flooding impacts, including mudslides and landslides in areas of steep terrain, across PR and the USVI. Soils are saturated and streamflows are elevated. Considering the antecedent conditions, any additional heavy rainfall will likely lead to rises on rivers and significant flooding impacts. .Alaska... Significant rises on Moose creek near Glennallen due to snowmelt runoff are expected and minor flooding is already occurring. The ice breakup front is 30 miles upstream from Circle as of Sunday. There is potential for minor to moderate flooding in Circle as a heavy run of ice moves through. Flooding will be possible as an ice jam near Akiak, causing minor flooding, and Tuluksak moves downstream. //Kirkpatrick $$