411
AGUS74 KWCO 101517
HMDNWC

National Hydrologic Discussion - EXPERIMENTAL
NWS National Water Center - Tuscaloosa AL
1015 AM CDT SUN AUG 10 2025

.Synopsis...
Considerable flooding impacts remain possible for portions of the Upper
Midwest... Isolated flash flood potential to continue across the
Southeast...

.Central Plains through the Upper Midwest...
Considerable flash, urban, and riverine flooding impacts remain possible
today across eastern IA, far-northern MO, northwestern IL, and southern WI
as additional convective complexes bring heavy rainfall to this already
vulnerable region. Locally considerable flash and urban flooding impacts
are also possible beginning late tonight across southeastern KS and
west-central MO as the same storm system impacts this region as well.

The complex of storms ongoing across northeastern IA, northwestern IL, and
southern WI has already caused significant flash and small stream flooding
impacts across portions of the Milwaukee metro overnight and earlier this
morning, with some portions of the metro receiving nearly a foot of
rainfall (MRMS QPE). While relative storm motions will pick up speed over
the course of the morning, flooding impacts are still likely across this
region, given training and intense rainfall rates (2"+/hr), particularly
over urban areas and locations that received heavy rainfall overnight.
Guidance from the HRRR-forced National Water Model (NWM) is indicating
scattered small stream responses across much of IA, northwestern IL, and
southern WI, with peak flows expected by early this afternoon, suggesting
additional impacts possible. Corresponding AEPs, per the High Flow
Magnitude Forecast, are indicating the potential for additional significant
small stream responses, as AEPs below 10% are noted across the considerable
region, with AEPs as low as 2% noted near the Milwaukee metro. The HRRR has
generally been underestimating the rainfall rates with this complex of
storms, so the responses noted by the NWM are likely underdone in extent
and magnitude. Additional heavy rainfall later today/tonight may generate
new/renewed flooding impacts across this region.

In regards to river flooding, current forecasts indicate isolated moderate
and major flooding along the Root and Fox rivers in WI (in/near the
Milwaukee metro), and isolated action stage rises and isolated minor
flooding in eastern IA. Additional areas of significant river flooding
remain possible, but less likely, as the overall QPF footprint has
decreased in magnitude over the past 24 hours. River ensemble (HEFS) and
PQPF guidance continues to show the potential for moderate and major river
flooding across eastern IA, northwestern IL, and southern WI. However,
confidence in this potential has decreased from yesterday given variability
in model guidance and the placement of the heaviest QPF.

Further south into eastern KS and western/central MO, locally considerable
flash and urban flooding remains possible beginning tonight as the main
axis of heavy precip shifts south into this region. Although antecedent
conditions are drier here (near normal streamflows (USGS 10 - 50% RSM, 0 -
10 cm NASA SPoRT), the expected training nature of the rainfall, coupled
with the intensity, will likely quickly overwhelm current capacities and
generate rapid runoff into nearby streams and urban drainages. The
HRRR-forced NWM is  indicating isolated small stream responses across
portions of eastern KS through central MO for later today.  There is still
some uncertainty in the exact placement and magnitude of impacts given the
modeled QPF differences between various models. However, given the
potential for heavy rainfall/intense rainfall rates, flash and urban
flooding remains likely, some of which may be locally significant. Isolated
areas of river flooding are also possible, especially across quick
responding basins in southeastern KS/western MO.

.Southeast...
The potential for isolated flash flooding in portions of northern FL, the
FL Peninsula, and along the coasts of GA and the Carolinas will continue
through at least day 2 (Mon) as slow moving convection persists across the
region. Soils are saturated in these areas (50 - 90% RSM, 0 - 10 cm NASA
SPoRT), which would generally suggest an increased vulnerability to rapid
runoff and subsequent hydrologic responses. However, urban flooding and
areal ponding are the greatest threats here, given the prevalence of karst
topography/significant underground storage and seepage across FL, and well
draining/sandy soils across much of the Southeast Coastal Plain, helping to
mitigate widespread flooding impacts. The HRRR-forced NWM is indicating
isolated small stream responses across the FL Peninsula and along the
immediate coasts of GA and the Carolinas.Impacts will be greatest in
low-lying, urban, and poorly drained areas and will be determined by slow
storm motions and robust rainfall rates (1 - 2"+/hr). Elevated flows and
isolated minor river flooding will continue across GA and SC through mid
week as runoff from recent rainfall routes downstream.

//JDP





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