745
AGUS74 KWCO 282001
HMDNWC

National Hydrologic Discussion - EXPERIMENTAL
NWS National Water Center - Tuscaloosa AL
300 PM CDT MON SEP 28 2026

...Considerable flash flooding impacts possible in the Southwest into the
Central High Plains... Locally considerable flash and river flooding impacts
possible for the Central Plains into the Middle Mississippi Valley... Locally
considerable flash, urban, and river flooding possible across the Southern
Plains into the Ozarks...

.Southwest into the Central High Plains...
Considerable flooding impacts are possible for portions of southwest,
central and northeast NM into the TX Panhandle today through Tuesday as
deep tropical moisture continues to surge into the region. Due to previous
rainfall over the past week, portions of NM and the TX Panhandle are more
sensitive to heavy rainfall. Near surface soils are now at about 50%
saturation (RSM NASA SPoRT) across much of NM and into the TX Panhandle
since a short break in heavy rainfall over the weekend allowed for some
soil and channel storage recovery. However, streamflows are still elevated
(USGS), suggesting the potential for efficient runoff into still-elevated
streams as heavy rainfall returns. Both the GFS- and NBM-forced National
Water Model (NWM) Medium Range Forecasts (MRF) are showing the strongest
responses across NM and into the TX Panhandle with many responses starting
within the next 12 hours and continuing through Tuesday. The NWM Maximum
High Flow Magnitude Forecasts continue to show scattered areas of stream
responses across NM with annual exceedance probabilities lower than 10%
(higher magnitude flows) suggesting the potential for out of bank flows.
Given the widespread possibility for heavy rainfall, the remainder of this
region is highlighted in a Limited Flood Threat indicating the potential
flash and small stream flooding impacts, some of which may be locally
considerable, particularly near burn scars, low-water crossings, and
mountain drainages or areas of steep terrain.

.Central Plains into the Middle Mississippi Valley...
Flash, urban, and river flooding impacts are possible starting Tuesday as
rainfall returns to the region. Some areas could see 3 - 5" of rainfall
Tuesday into Wednesday (WPC). Eastern NE and IA are more saturated due to
recent rainfall making those areas much more vulnerable to flooding
impacts, some of which may be locally considerable depending on where
highest rainfall totals occur. NWM MRF signals have shown better agreement
in most recent runs and are highlighting the strongest potential for rapid
onset flooding across eastern NE and central IA, as well as scattered areas
of annual exceedance probabilities lower than 10% (higher magnitude flows),
suggesting the potential for out of banks flows. Additionally, river
ensemble forecasts (HEFS) are showing a robust river response with
scattered moderate flooding at the 50% chance exceedance. With these strong
responses, confidence has increased in the potential for locally
considerable flooding impacts across the region.

.Southern Plains into the Ozarks...
Locally considerable flash, urban and river flooding threat is solidifying
for later this week across the region. Heavy rainfall (3 - 5" and locally
higher amounts) will begin late Wednesday and continue into early Friday.
Antecedent conditions are very dry which should allow for some initial
infiltration; however, given the potential for high rainfall rates and
longer duration rainfall, soils could eventually be overwhelmed leading to
runoff. The NWM is suggesting robust smaller stream responses beginning
early Thursday morning. Both the GFS- and NBM-forced NWM have lined up well
with robust streamflow responses across south-central TX suggesting
increasing confidence in rapid stream rises and locally considerable flash
and urban flooding impacts. NWM signals are also present northward into
central OK and the western Ozarks however, they are currently more
isolated. River flooding will also be a threat for this event. River
ensembles are suggesting the potential for river rises across similar
basins to the NWM responses. Larger rivers will see a delayed response late
this week and into the weekend as water routes downstream.

.Southern New England...
With the diminishing flood threat, we dropped this region from this
afternoons FHO issuance.


//EAS/Cordak

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