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Hydrometeorological Discussion
Issued by NWS Tuscaloosa, AL
Issued by NWS Tuscaloosa, AL
459 AGUS74 KWCO 021521 HMDNWC National Hydrologic Discussion - EXPERIMENTAL NWS National Water Center - Tuscaloosa AL 1015 AM CDT TUE JUL 2 2024 .Synopsis... Renewed flooding, isolated flash flooding possible this week for the Upper and Middle Mississippi Valley... Daily convection continues across the Four Corners Region... Isolated heavy rainfall through Tuesday across portions of Puerto Rico as Hurricane Beryl tracks south of the island... Increased snowmelt and glacier runoff, heavy rainfall expected in Alaska... .Discussion... .Upper and Middle Mississippi Valley... Moderate to major river flooding is ongoing across far southeast SD, southern MN, northern IA and MO and is forecast through this week along the Missouri (moderate) and Mississippi (moderate to major) river mainstems. Rainfall continues across the region through day 3 (Thu), though light rainfall could persist through day 6 (Sun). Ample deep layer soil moisture remains in place across southeastern SD, southern MN, IA, and WI (60 - 75% RSM 0 - 100 cm NASA SPoRT), suggesting that the already elevated/flooded rivers across the region will likely respond fairly efficiently to the runoff from the additional rainfall. Generally 2 - 4" inches of rainfall is expected across the area through the next 7 days (thru Mon). At the minimum, this rainfall will likely cause delayed recessions of ongoing flooding and isolated flash flooding. Given those conditions, river flooding is also possible, including the potential for new and renewed rises at moderate and/or major flood stage (HEFS, CR Ensemble QPF hydrographs) if heavier rainfall totals occur. The National Water Model (NWM) Short Range Forecast (SRF) as well as Medium Range Forecast (MRF), continue to indicate rapid-onset flooding probabilities generally between 25 - 50% with corresponding annual exceedance probabilities between 4 - 20% on many smaller tributary rivers across the aforementioned region. With ongoing flooding and wet soils, significant impacts cannot be ruled out. .Four Corners Region... Daily convection will continue to bring the potential for isolated significant flash flooding in arroyos, slot canyons, dry washes, urban areas, and recently burned regions. This potential will persist through the end of the week, with the highest chances occurring through day 2 (Wed), particularly in NM, southeastern AZ, and eastern CO. Locations that have received multiple rounds of rainfall over the past week are most susceptible to new flooding impacts. .Puerto Rico... Showers and thunderstorms through this evening across Puerto Rico will bring 1 to 2 inches of rainfall, with the potential for isolated flooding impacts. Streamflows across this portion of the island are generally normal to above normal in comparison to both the daily and annual climatological normals (USGS), and soils range from dry to wet but not saturated (NASA SPoRT). Considering these antecedent conditions and the convective nature of the rainfall, flooding impacts should remain isolated. .Alaska... Recent warm temperatures continue to lead to increased snowmelt and glacier runoff, leading to elevated flows and minor flooding on a few rivers in southern AK. Minor flooding along the Chilkat River near Klukwan continues, and elevated flows continue along the Klutina River near Copper Center and the Nuyakuk River northeast of Dillingham. On days 2 and 3 (Wed and Thu), heavy rainfall is expected across western portions of the Brooks Range (2 - 4") and portions of the Interior, including Fairbanks (1 - 2"). Later in the forecast period, on day 6 (Sun), another heavy round of rainfall will affect southern AK (1 - 2"). This could lead to rapid rises on streams and rivers, potentially leading to flooding in affected areas. //Wood/Kirkpatrick $$