####018004136#### AGUS74 KWCO 291518 HMDNWC National Hydrologic Discussion - EXPERIMENTAL NWS National Water Center - Tuscaloosa AL 1015 AM CDT MON APR 29 2024 .Synopsis... Flooding impacts remain possible across portions of the Central and Southern Plains into the Midwest... East Texas and the Lower Mississippi Valley... Puerto Rico...Runoff from snowmelt possible in Alaska...Flooding possible later this week in American Samoa...Ongoing flooding across the Great Basin and Intermountain West... .Discussion... .Central and Southern Plains into the Midwest... Widespread minor to isolated major river flooding is ongoing or forecast over portions of KS, MO, and western IL where widespread 1.5 to 2.5" of rain have fallen in the last 72 hours (MRMS) with areas of 3 - 6+" in KS and MO. Additional periods of rainfall are possible across these regions again on days 2 - 4 (Tue - Thu), potentially generating new and renewed flooding impacts to already saturated antecedent conditions. The heaviest rainfall will take place on day 3 (Wed) where areas of northeast KS, southeast NE, southwest IA and northwest MO could see additional flash and small stream flooding. Top soils in these regions are wet to saturated (0 - 10 cm RSM, NASA SPoRT) and streamflows are running much above normal suggesting that out-of-bank rises are likely to continue. The National Water Model (NWM) Medium Range Forecast (MRF) is signaling rapid-onset flooding probabilities (ROF) between 25 - 50% and corresponding annual exceedance probabilities around 50% with localized responses near 2% increasing confidence in the potential for continued impacts throughout the week. .East Texas and the Lower Mississippi Valley... The threat for locally heavy rainfall and resultant flooding will shift to southeast LA and portions of MS today bringing the potential for flash, urban, and small stream flooding impacts. Top-soils are somewhat dry (0 - 10 cm RSM 40 - 50 %) across southern MS and southeast LA, however, given the intensity of the rainfall, these conditions may be quickly overwhelmed and localized flooding impacts are possible. The NWM Short Range Forecast (SRF) continues to signal ROF probabilities generally between 25 - 50% with localized probabilities of 75%, specifically in areas near the Gulf Coast in LA. Corresponding AEPs are generally at or near 2% in the same area, suggesting confidence in significant stream rises and out-of-bank flows. While light rainfall persists on day 2 (Tue), additional moderate to localized, heavy rainfall is forecast on days 3 - 4 (Wed - Thu) in portions of east TX, northern LA and AR and again in east TX on days 6 - 7 (Sat - Sun). Confidence is low in the exact timing and placement of this next event but given wet to saturated soil conditions and past rainfall, this area will be prone to quicker runoff with the chance of renewed and new river rises. .Puerto Rico and the USVI... Showers will continue this morning across portions of PR and the USVI and may generate urban and small stream flooding impacts. After a brief reprieve on day 2 (Tue), a wet pattern will return on day 3 (Wed) and will continue through the weekend. Given already saturated soils, river rises and mudslides are possible, especially in areas of steep terrain. Alaska... Runoff from snowmelt in areas of the Copper River Basin may bring flooding impacts to the region through day 3 (Wed). Moose Creek near Glennallen may have out-of-bank flows. American Samoa... Precipitation will increase through the week bringing the potential for flash flooding. .Great Basin and Intermountain West... Elevated flows will continue along area rivers, creeks, and streams across portions of southern ID and northern NV in response to runoff from mid-to-high elevation snowmelt and recent rainfall. Isolated minor to moderate river flooding is ongoing through this week. //Kirkpatrick $$