677
AGUS74 KWCO 081521
HMDNWC

National Hydrologic Discussion - EXPERIMENTAL
NWS National Water Center - Tuscaloosa AL
1020 AM CDT FRI AUG 8 2025

.Synopsis...
Significant flood potential for portions of the Upper Midwest... Isolated
flash flood potential across the Southeast...

.Upper Midwest...
Considerable flash, urban, and riverine flooding impacts are likely this
weekend into early next week as QPF guidance suggests 2 consecutive days of
heavy rainfall day 2 (Sat) through day 3 (Sun) (2 - 4"+ each day, totals
could approach 5 - 10") across eastern IA, far northern MO, northwest IL,
and southern WI. The best potential for overlap of consecutive days of
heavy rain looks to be across eastern IA where basins are already
vulnerable to additional rainfall (and there is ongoing elevated
flows/river flooding). Streamflows are running above normal (USGS) and
top-layer soils remain moist after yesterdays rainfall, therefore this
additional QPF will be enough to elicit renewed and new river flooding  by
early next week. Significant river flooding is possible. The GFS and
NBM-forced National Water Model (NWM) forecasts show an increase in both
areal coverage and magnitude of response across eastern IA into southwest
WI and northwest IL in comparison to signals from yesterday. The number of
basins showing potential for rapid onset flooding has increased, and there
are now some indications for higher magnitude flows in the 10 - 20% AEP
range. This in conjunction with a consistent placement/increasing magnitude
QPF forecast from WPC provides increased confidence in potential for
significant flooding impacts late this weekend into early next week.

Further north, multiple rounds of convection through tonight poses a threat of flash,
urban, and small stream flooding across southeast ND into northern MN. Rain
from this morning has moistened top-layer soils, and streamflows are near
normal to slightly above normal, so isolated nuisance flooding will be
possible, but the fast forward propagation of the heavy rain/short
residence time in any particular basin should mitigate just about all of
the hydrologic response.

.Southeast...
Elevated flows and isolated minor river flooding will continue across GA
and the Carolinas through this weekend in response to recent rainfall.
Additionally, isolated flash flooding in low-lying, urban, and poor
drainage areas will be possible across southeast AL, FL, GA, and the
Carolinas through this weekend with daily afternoon/evening convection.
Some areas, which have been primed by recent rainfall, are showing soil
moistures around 50 - 70% saturation (NASA SPoRT, 0 - 10 RSM) leaving what
seems like little room for infiltration/increased potential for rapid
runoff, yet soils in the region are notoriously well draining and can be
expected to rapidly give room for more moisture, as has been noted in the
soil moisture change over the past 24-hours.

//JEC

$$