


Hydrometeorological Discussion
Issued by NWS Tuscaloosa, AL
Issued by NWS Tuscaloosa, AL
142 AGUS74 KWCO 181457 HMDNWC National Hydrologic Discussion - EXPERIMENTAL NWS National Water Center - Tuscaloosa AL 957 AM CDT SAT OCT 18 2025 .Synopsis... Widespread rainfall and isolated flooding potential across the Middle Mississippi Valley into the Great Lakes...Isolated flash flood potential across American Samoa through this weekend... A series of atmospheric rivers expected late week for the Pacific Northwest... Daily afternoon isolated flooding potential for Puerto Rico... .Middle Mississippi Valley into the Great Lakes... Showers and thunderstorms are expected across the entire region through tonight, with potential for heavier rainfall totals across southern MO/northern Ozarks, which will bring an isolated threat for flash flooding. The soils across the entire region remain dry and as such much of this rainfall is likely to be beneficial. However, pockets of intense or training rainfall can overwhelm dry soils, and therefore, lead to enhanced overland flow and flash flooding potential, especially across the complex terrain of the northern Ozarks. Regardless, the concern for widespread flooding concerns remains low due to the progressive nature of the system. The National Water Model is showing isolated potential for rapid river rises across south-central MO for this afternoon, but widespread riverine responses are not expected, and flooding should remain localized. .American Samoa... An active trough is forecast to bring heavy rainfall to all the islands through the weekend which may cause instances of flash flooding and landslides. .Pacific Northwest... A series of atmospheric rivers is forecast late in the period which may bring isolated urban and small stream flooding beginning late next week. Rainfall through mid week looks to be beneficial to the region as soils are dry and streamflows are low which is to be expected at the beginning of the wet season, however numerous periods of repeated rounds of rainfall late week through next weekend could begin to become concerning, as cumulative totals begin approaching 7 - 10"+ across far northwest OR and western WA along and west of the Cascades, including basins draining the Olympics. While the extended range typically is associated with reduced confidence in the forecast, much of the model guidance has been showing consistency in some appreciable rainfall possible along with ensemble river guidance (HEFS) beginning to pick up increasing chances of potential river flooding, particularly in basins draining the western slopes of the Cascades in WA. .Puerto Rico... Afternoon showers and thunderstorms will continue across the island through the weekend into early next week which may bring isolated flooding to the island. While there is a low chance of flash flooding, some isolated areas of urban and small stream flooding are possible. Additional National Water Center products are available at www.weather.gov/owp/operations This product will begin to be issued twice daily, with new issuance times, beginning approximately 3 November 2025. The routine primary issuance time of the product will be at 20 UTC, with routine daily updates to the discussion being completed around 7 AM Central Time. //JEC $$