Area Hydrologic Discussion
— Latest
Threat
POTENTIAL IMPACTS: Flash and urban flooding WHERE: Central and northeastern Iowa, southeastern Minnesota, and WHEN: Through late tonight
Rainfall & Conditions
QPF: 2 - 4", locally 5+" (HRRR/RRFS/WPC) Rainfall Rates: 1 - 2"/hr, locally higher (HRRR/RRFS/WPC) Relative Soil Moisture: 40 - 70% RSM (SPoRT 0 - 10 cm) Streamflows: Above normal to high (observed, USGS)
Discussion
Scattered thunderstorms will continue to expand in coverage and intensity across the area of concern through this evening, potentially generating flash and urban flooding impacts, along with sharp rises on small streams. While above-normal temperatures over the past several days have allowed for some recovery in soil storage capacity, intense rainfall rates and training/repeating storms are expected, which will allow for substantial runoff into streams and rivers with reduced in-channel storage and suggest an environment favorable for flooding. Standing water in low-lying and typical flood-prone areas and rapid rises on quick-responding streams/creeks are possible, especially in more urban areas. New and renewed river flooding is also possible across portions of eastern Iowa and southwestern Wisconsin where flooding is already ongoing.
The HRRR-forced National Water Model (NWM) has been consistent in highlighting the potential for small stream responses across the area of concern, with the highest probabilities (greater than 50%) across northeastern Iowa and southeastern Minnesota. This also coincides with where the greatest potential for significant stream rises exists, as the latest guidance from the High Flow Magnitude Forecast suggests annual exceedance probabilities of 10 - 20%, with values as low as 2% in this general region. Peak flows on small streams across the region are expected as early as late evening. Widespread significant impacts aren't expected, although they cannot be entirely ruled out given the likelihood of training convection and robust rainfall rates.
Addressed To
WFO: GRB, ARX, MPX, DMX, FSD, OAX, DVN, MKX RFC: KRF, MSR, WPC
000 AGUS74 KWCO 082220 AHDNWC Area Hydrological Discussion #136 - EXPERIMENTAL NWS National Water Center - Tuscaloosa, AL 514 PM CDT Wed Jul 08 2026 POTENTIAL IMPACTS: Flash and urban flooding WHERE: Central and northeastern Iowa, southeastern Minnesota, and southwestern Wisconsin WHEN: Through late tonight FORECAST RAINFALL AND ANTECEDENT CONDITIONS... QPF: 2 - 4", locally 5+" (HRRR/RRFS/WPC) Rainfall Rates: 1 - 2"/hr, locally higher (HRRR/RRFS/WPC) Relative Soil Moisture: 40 - 70% RSM (SPoRT 0 - 10 cm) Streamflows: Above normal to high (observed, USGS) DISCUSSION... Scattered thunderstorms will continue to expand in coverage and intensity across the area of concern through this evening, potentially generating flash and urban flooding impacts, along with sharp rises on small streams. While above-normal temperatures over the past several days have allowed for some recovery in soil storage capacity, intense rainfall rates and training/repeating storms are expected, which will allow for substantial runoff into streams and rivers with reduced in-channel storage and suggest an environment favorable for flooding. Standing water in low-lying and typical flood-prone areas and rapid rises on quick-responding streams/creeks are possible, especially in more urban areas. New and renewed river flooding is also possible across portions of eastern Iowa and southwestern Wisconsin where flooding is already ongoing. The HRRR-forced National Water Model (NWM) has been consistent in highlighting the potential for small stream responses across the area of concern, with the highest probabilities (greater than 50%) across northeastern Iowa and southeastern Minnesota. This also coincides with where the greatest potential for significant stream rises exists, as the latest guidance from the High Flow Magnitude Forecast suggests annual exceedance probabilities of 10 - 20%, with values as low as 2% in this general region. Peak flows on small streams across the region are expected as early as late evening. Widespread significant impacts aren't expected, although they cannot be entirely ruled out given the likelihood of training convection and robust rainfall rates. GRAPHICAL REPRESENTATION: weather.gov/owp/operations-ahd Additional National Water Center products are available at: weather.gov/owp/operations //JDP ATTN...WFO...GRB...ARX...MPX...DMX...FSD...OAX...DVN...MKX ATTN...RFC...KRF...MSR...WPC