952
AGUS74 KWCO 111528
HMDNWC

National Hydrologic Discussion - EXPERIMENTAL
NWS National Water Center - Tuscaloosa AL
1015 AM CDT MON AUG 11 2025

.Synopsis...
Lingering flood potential and ongoing river flooding in the
Central/Southern Plains through the Upper Midwest... Isolated flash flood
potential continues across the Southeast... A glacier dam release is
possible on the Mendenhall River downstream of Suicide Basin in Alaska...

.Central/Southern Plains through the Upper Midwest...
Flash and urban flooding is possible in OK and far northern TX today in
response to heavy rainfall. Topsoils are dry (10 - 20% RSM, 0 - 10cm, NASA
SPoRT) and streams are generally running near normal flows (USGS),
suggesting small stream/river flooding is unlikely to materialize. The
HRRR-forced National Water Model (NWM) is only showing scattered
deterministic rapid-onset flooding (ROF) signals and minimal response in
the high flow magnitude forecast, supporting the notion of the primary
threats being flash/urban in nature.

The flood threat looks to be decreasing in KS and MO today as most of the
heavy rainfall threat will be over by late morning, and isolated convective
rainfall this afternoon does not appear to be widespread enough or have
intense enough rainfall rates to be of particular concern (HRRR/RRFS).
Minor to moderate river flooding is ongoing in the Milwaukee, WI area. Most
rivers are in recession at this point, with the exception of the Fox River
which is forecast to crest later today. High flows persist across IA, but
only one forecast point remains in minor flood status. With no significant
rainfall in the forecast, rivers should be able to recede unimpeded.

.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 today as slow moving convection persists across the region. Soils
have been primed from recent rainfall, (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 NWM Analysis and Assimilation
service indicates ongoing streamflows in the 50 - 2% AEP range along
coastal SC/GA, and the HRRR-forced NWM indicates additional isolated small
stream responses are possible. The NWM indicates little to no stream
response in FL, but impacts are still possible in urban and poorly drained
areas. In general, the magnitude of impacts will be determined by whether
any slow moving storm cells with high rainfall rates (1 - 2"+/hr) sets up
over an urban area. Elevated flows and isolated minor river flooding will
continue across GA and SC through mid week as runoff from recent rainfall
routes downstream.

.Alaska...
Mendenhall Glaciers Suicide Basin glacier dammed lake near Juneau, AK is
full and has begun to overtop. Flooding along the Mendenhall River is
likely once the dam releases. Rain is expected to continue through today in
northwest AK and along the Gulf of Alaska coast. No significant run-off
induced flooding is expected, but some out-of-bank rises are possible.

//Bliss



$$