AGUS74 KWCO 161154 HMDNWC National Hydrologic Discussion - EXPERIMENTAL NWS National Water Center - Tuscaloosa AL 700 AM CDT THU APR 16 2026 .Update... The Considerable impact area across the Mariana Islands has been removed as the heavy rainfall and flooding associated with Typhoon Sinlaku has subsided. The Limited impacts area in the Lower Great Lakes has also been removed as the threat for flooding has ended. No changes to both the Limited and Considerable impact areas across the Upper Great Lakes into the Middle Mississippi Valley however, notable timing changes have been made to the talking points across those regions to account for ongoing river flooding through early next week and the potential for new and renewed flooding impacts tomorrow into early Saturday. //JDP Previous discussion as follows: ...Considerable flooding impacts ongoing in the Mariana Islands... Considerable rain and snowmelt-driven small stream and river flooding in the Upper Great Lakes with additional flooding into the Middle Mississippi Valley possible...Isolated flooding possible in the Lower Great Lakes... .Mariana Islands... Considerable flooding is ongoing for the Mariana Islands as Typhoon Sinlaku moves through the region, bringing widespread heavy rainfall. Periods of torrential rain and embedded thunderstorms through late Wednesday (Eastern Time) are expected to produce significant flash flooding. Rainfall is expected to taper off through the evening, however additional rainfall totals of 2 to 6 inches are possible. The prolonged rainfall has saturated soils, maintaining the potential for mudslides, especially across central and southern Guam. Substantial coastal impacts are also expected across the CNMI. .Upper Great Lakes into the Middle Mississippi Valley... Considerable river and small stream flooding is ongoing and forecast across portions of Michigan, Wisconsin, and Illinois through the weekend. Widespread moderate to major river flooding is forecast, some of which is expected to exceed record stages. Flash and urban flooding will also be possible through the overnight hours as additional heavy rain moves through the region. Elsewhere in the region, minor river flooding is ongoing with new and renewed river small streams and flooding expected through the week. The hydrologic environment remains primed, and additional rainfall Friday into Saturday may produce new or renewed flood impacts through the weekend. .Lower Great Lakes... Isolated flash, urban, and small stream flooding will be possible over portions of Ohio, Pennsylvania, and New York as heavy rainfall moves through the region through Thursday. Soils remain wet over the region with little space for infiltration. River flooding is not expected at this time, however rises to action stage may be possible through the weekend. //Fontenot Additional National Water Center products are available at www.weather.gov/owp/operations $$