Hydrometeorological Discussion
Issued by NWS Tuscaloosa, AL
Issued by NWS Tuscaloosa, AL
874 AGUS74 KWCO 231522 HMDNWC National Hydrologic Discussion - EXPERIMENTAL NWS National Water Center - Tuscaloosa AL 1015 AM CDT SUN JUN 23 2024 .Synopsis... Additional rounds of rainfall in the Northern Plains, Upper Midwest, Upper Great Lakes and the Ohio Valley... Flash flooding possible in the Four Corners region and Northeast...Snow-melt induced flooding in Alaska... .Discussion... .Northern Plains, Upper Midwest , Upper Great Lakes and the Ohio Valley... Additional rounds of rainfall continue early next week through the end of the week bringing the potential for flash, urban and small stream flooding. Any rainfall lingering today and on day 2 (Mon) will be on the lighter side and is expected to have minimal hydrologic impacts while days 3, 5 and 6 will be the heaviest (Tue, Thu, Fri). Widespread moderate to major river flooding is ongoing and expected across southeast SD, southern MN, and northern IA into next week. Record forecasts are ongoing and/or forecast for many rivers seen over the same areas. Soil conditions are saturated in areas of southeastern SD, northern IA, southern MN and central WI (0 - 100 cm, 75 - 90% RSM, NASA SPoRT) given that widespread rainfall amounts of 3 - 10" (MRMS) have fallen over the past 72 hours. Streamflows are running much above normal for all days of the year, suggesting limited to no storage capacity to store additional rainfall and any remaining soil capacity will likely be overwhelmed. Each additional round of rainfall will serve to further compound the flood potential. The National Water Model (NWM) Medium Range Forecast (MRF) continues to highlight much of the same region that has just seen past rainfall including areas of SD, MN, IA, and WI as well as portions of MI. Rapid-onset flooding probabilities are near 25 - 50% in these areas with corresponding annual-exceedance probabilities (AEPs) near 50% Given these conditions, any given rainfall may delay recessions and may potentially cause some renewed rises. .Four Corners... Moisture continues to remain in place over the region through the rest of the week, specifically in areas of NM and AZ, bringing locally heavy rainfall and the potential for flash flooding with days 4 - 5 (Wed - Thu) likely being the biggest threat. Areas that received past rainfall may continue to see a threat of flash flooding and excessive runoff. The flood threat is highest in areas on recent burn scars, slot canyons, dry washes and where training is likely to occur. .Northeast... Moderate to heavy rainfall continues to impact the region bringing the potential for localized flash flooding, especially in areas where training has occurred and in primarily urban areas today through day 2 (Mon) and then again on day 4 and 7 (Wed and Sat). Soils are near normal (60 - 75%, 0 - 10 cm, NASA SPoRT) and near to below mean annual streamflows (USGS) suggesting there is still sufficient infiltration capacity overall to capture runoff. These factors will help to mitigate any widespread hydrologic responses and limit the threat to urban, low-lying, and poor drainage areas. .Alaska... Warming temperatures continue to cause snow and ice melt at high elevations, leading to rivers running high in areas across Southcentral Alaska. Minor flooding on the Chilkat River near Klukwan continues as well as high water on the Nuyakuk River near Dillingham. The Skwentna and Yentna Rivers will also likely have high water with out-of-bank conditions by day 2 (Mon). //Kirkpatrick $$