Area Hydrologic Discussion
— Latest
Threat
POTENTIAL IMPACTS: Flash and urban flooding WHERE: Iowa WHEN: Through tomorrow morning
Rainfall & Conditions
QPF: 1 - 4" locally 5" (HRRR) QPE: 0 - 4" locally 10" (past 48 hr.-MRMS) Rates: 1 - 2"+ (HRRR/WPC) Soil Moisture: Variable (0 - 10cm RSM NASA SPoRT) Streamflows: Normal to Above Normal (USGS Gage Data)
Discussion
Several rounds of thunderstorms are expected to bring heavy rainfall through central Iowa through tomorrow morning, potentially generating flash and urban flooding. According to the SPoRT RSM, topsoil antecedent conditions indicate previous rainfall has increased the relative soil moisture throughout the area of concern. As such, the expected rainfall will continue to decrease infiltration capacity and increase vulnerability to excessive runoff and flooding. Previous storm events were focused on the western side of Iowa, with isolated heavy rainfall totals of near 10'' over the past 48 hours near Graettinger in the northwest portion of the state. While drier soils are in place over portions of central/southern Iowa, the repeated nature of the convection, as well as the potential for heavy rainfall in short periods of time (localized totals up to 5") will likely overwhelm current conditions and lead to flooding.
The NWM short range forecast has been consistently indicating the potential for rapid onset flooding across the area of concern through the overnight hours, with basin-average probabilities of 25 - 75% and localized probabilities exceeding 75% north/northwest of the Des Moines metropolitan area. Ensemble river guidance is suggesting some basins in the area of concern may experience isolated river flooding. As such, localized urban or low-lying areas where training or heavier rainfall rates materialize may see quick-response runoff, rises on small streams and rivers, and flash flooding is possible.
Addressed To
WFO: ARX, DMX, FSD, OAX, EAX, DVN, MKX RFC: KRF, MSR, WPC
000 AGUS74 KWCO 082341 AHDNWC Area Hydrological Discussion #203 - EXPERIMENTAL NWS National Water Center - Tuscaloosa, AL 634 PM CDT Tue Sep 08 2026 POTENTIAL IMPACTS: Flash and urban flooding WHERE: Iowa WHEN: Through tomorrow morning FORECAST RAINFALL AND ANTECEDENT CONDITIONS... QPF: 1 - 4" locally 5" (HRRR) QPE: 0 - 4" locally 10" (past 48 hr.-MRMS) Rates: 1 - 2"+ (HRRR/WPC) Soil Moisture: Variable (0 - 10cm RSM NASA SPoRT) Streamflows: Normal to Above Normal (USGS Gage Data) DISCUSSION... Several rounds of thunderstorms are expected to bring heavy rainfall through central Iowa through tomorrow morning, potentially generating flash and urban flooding. According to the SPoRT RSM, topsoil antecedent conditions indicate previous rainfall has increased the relative soil moisture throughout the area of concern. As such, the expected rainfall will continue to decrease infiltration capacity and increase vulnerability to excessive runoff and flooding. Previous storm events were focused on the western side of Iowa, with isolated heavy rainfall totals of near 10'' over the past 48 hours near Graettinger in the northwest portion of the state. While drier soils are in place over portions of central/southern Iowa, the repeated nature of the convection, as well as the potential for heavy rainfall in short periods of time (localized totals up to 5") will likely overwhelm current conditions and lead to flooding. The NWM short range forecast has been consistently indicating the potential for rapid onset flooding across the area of concern through the overnight hours, with basin-average probabilities of 25 - 75% and localized probabilities exceeding 75% north/northwest of the Des Moines metropolitan area. Ensemble river guidance is suggesting some basins in the area of concern may experience isolated river flooding. As such, localized urban or low-lying areas where training or heavier rainfall rates materialize may see quick-response runoff, rises on small streams and rivers, and flash flooding is possible. GRAPHICAL REPRESENTATION: water.noaa.gov/operations/ahd Additional National Water Center products are available at: weather.gov/owp/operations //RK/JDP ATTN...WFO...ARX...DMX...FSD...OAX...EAX...DVN...MKX ATTN...RFC...KRF...MSR...WPC