Area Hydrologic Discussion
— Latest
Threat
POTENTIAL IMPACTS: Locally considerable flash, urban, and small WHERE: Northeastern Nebraska, southeast North Dakota, southwest WHEN: Through late tonight
Rainfall & Conditions
QPF: 3 - 5", locally higher amounts possible (HRRR/HREF/WPC) Soil Moisture: Below normal (0 - 10cm RSM NASA SPoRT) Streamflows: Below normal (USGS)
Discussion
Heavy rainfall is expected to expand across the region this afternoon and into the evening bringing the threat of locally considerable flash, urban, and small stream flooding. Antecedent conditions are generally on the dry side, particularly south of Sioux City, IA; however, any impacts will likely be driven by higher rainfall rates which could overwhelm the infiltration capacity of the soils and lead to rapid runoff. The HRRR-forced National Water Model (NWM) Short Range Forecast (SRF) has been consistently showing robust responses on smaller order streams across the area of concern over the last several runs, particularly across western IA. Probabilities for rapid-onset flooding (shown right) have also been increasing from run to run (25 - 75%), and thus increasing the confidence in rapid rises across the area. HRRR rainfall estimates have generally aligned with trends shown by other high-resolution guidance and current observations, supporting these responses. Additionally, the magnitude of the responses have also remained high with areas of lower AEPs (higher magnitude flows) and unit discharge values on smaller order streams (orders 1 - 2) greater than 400 cfs/sqmi and as high as 1000 cfs/sqmi, suggesting confidence in out of bank flows. Given these factors locally considerable flash, urban, and small flooding will be possible through late tonight.
Addressed To
WFO: DMX, FSD, OAX RFC: KRF, MSR, WPC
000 AGUS74 KWCO 061643 AHDNWC Area Hydrological Discussion #202 - EXPERIMENTAL NWS National Water Center - Tuscaloosa, AL 1137 AM CDT Sun Sep 06 2026 POTENTIAL IMPACTS: Locally considerable flash, urban, and small flooding WHERE: Northeastern Nebraska, southeast North Dakota, southwest Minnesota, and western Iowa WHEN: Through late tonight FORECAST RAINFALL AND ANTECEDENT CONDITIONS... QPF: 3 - 5", locally higher amounts possible (HRRR/HREF/WPC) Soil Moisture: Below normal (0 - 10cm RSM NASA SPoRT) Streamflows: Below normal (USGS) DISCUSSION... Heavy rainfall is expected to expand across the region this afternoon and into the evening bringing the threat of locally considerable flash, urban, and small stream flooding. Antecedent conditions are generally on the dry side, particularly south of Sioux City, IA; however, any impacts will likely be driven by higher rainfall rates which could overwhelm the infiltration capacity of the soils and lead to rapid runoff. The HRRR-forced National Water Model (NWM) Short Range Forecast (SRF) has been consistently showing robust responses on smaller order streams across the area of concern over the last several runs, particularly across western IA. Probabilities for rapid-onset flooding (shown right) have also been increasing from run to run (25 - 75%), and thus increasing the confidence in rapid rises across the area. HRRR rainfall estimates have generally aligned with trends shown by other high-resolution guidance and current observations, supporting these responses. Additionally, the magnitude of the responses have also remained high with areas of lower AEPs (higher magnitude flows) and unit discharge values on smaller order streams (orders 1 - 2) greater than 400 cfs/sqmi and as high as 1000 cfs/sqmi, suggesting confidence in out of bank flows. Given these factors locally considerable flash, urban, and small flooding will be possible through late tonight. GRAPHICAL REPRESENTATION: water.noaa.gov/operations/ahd Additional National Water Center products are available at: weather.gov/owp/operations //Smith ATTN...WFO...DMX...FSD...OAX ATTN...RFC...KRF...MSR...WPC