![National Oceanic and Atmospheric Administration](/build/images/header/noaa.d87e0251.png)
![National Weather Service](/build/images/header/nws.4e6585d8.png)
![United States Department of Commerce](/build/images/header/doc.b38ba91a.png)
Hydrometeorological Discussion
Issued by NWS Tuscaloosa, AL
Issued by NWS Tuscaloosa, AL
686 AGUS74 KWCO 041517 HMDNWC National Hydrologic Discussion - EXPERIMENTAL NWS National Water Center - Tuscaloosa AL 1015 AM CDT THU JUL 4 2024 .Synopsis... New and renewed river flooding and flash flooding threats continue across the Central Plains and the Upper to Middle Mississippi Valley...Heavy rainfall possible this weekend across South Texas...Isolated heavy rainfall today across portions of Puerto Rico... Increased snowmelt and glacier runoff, heavy rainfall to continue in Alaska... .Discussion... .Central Plains and the Upper to Middle Mississippi Valley... Moderate to major river flooding continues across portions of extreme southeastern SD, southern MN, and much of IA, with moderate to major flooding forecast along portions of the mainstem Missouri and Mississippi rivers through early next week. Scattered thunderstorms expected today and again on day 3 (Sat) may elicit flash and urban flooding, as well as new and renewed river flooding in already flooded areas. Across portions of the Central Plains and Mid-Mississippi Valley, rainfall overnight and early this morning has resulted in rapid rises to minor and moderate flood across portions of eastern KS. This complex of storms will persist across eastern MO and central/southern IL through at least midday, and may generate isolated incidences of flash and urban flooding, and rapid stream rises, especially in areas that received heavy rainfall yesterday. The latest HRRR-forced National Water Model (NWM) indicates scattered small stream responses across much of northeastern MO and through central IL through mid-morning, with peak flows expected within the same time frame. Corresponding annual exceedance probabilities, per the High Flow Magnitude forecast, suggest that most stream rises in this region should remain within the channel however, some locally significant rises are possible across eastern MO, as AEPs in this region are as low as 2%. Additional rainfall this afternoon across this same region (KS/MO/IL) may generate new and renewed flooding as soils and streamflows will have limited recovery time in advance of this next round of storms. Impacts will be highly dependent on storm motions and the intensity of rainfall. Further north across SD, MN, IA, and WI, flash and urban flooding is possible through early day 2 (Sat) as storms impact this already saturated region. Despite a brief reprieve in rainfall in recent days, much of this area still has extensive river flooding and there is very little infiltration capacity due to wet soils, so it will not take much rainfall to generate hydrologic responses. All forcings of the NWM indicate scattered to widespread small stream responses across this region within the next 24 hours, with peak flows expected to begin on day 2 (Fri) runoff routes into the stream network. Corresponding AEPs from the High Flow Magnitude forecast shows that most rises will be modest, although some locally significant rises cannot be ruled out in areas of heavier rainfall. South Texas... Periods of tropical rainfall associated with Hurricane Beryl may impact portions of the Hill Country, Deep South TX, and the Rio Grande Valley on days 4 - 6 (Sun - Tue). Ahead of this expected rainfall, antecedent conditions are generally dry, as relative soil moisture (per NASA SPoRT) is low (less than 30%, 0 - 10 cm) and streamflows are generally below annual median values for this time of year, which suggests that at least initially, there is ample infiltration capacity for this rainfall. However, confidence in the exact location and magnitude of potential flooding remains uncertain and is highly dependent on the track and intensity of Beryl. .Puerto Rico and the USVI... Urban and small stream flooding is possible across the islands as a tropical wave brings periods of heavy rainfall through early day 2 (Fri). .Alaska... Periods of moderate to heavy rainfall (1 - 2"+) will continue into the weekend across much of the Brooks Range and Interior, which may enhance runoff, generate rapid rises and rivers and streams, and potentially lead to flooding. Elsewhere, elevated flows and isolated minor flooding from increased snowmelt and glacial melt continues along the Klutina River near Copper Center and the Nuyakuk River northeast of Dillingham. //Pritchard $$