315
AGUS74 KWCO 141517
HMDNWC

National Hydrologic Discussion - EXPERIMENTAL
NWS National Water Center - Tuscaloosa AL
1015 AM CDT MON JUL 14 2025

.Synopsis...
Locally considerable flooding possible in Texas and the Mid-Atlantic into
the Northeast... Isolated flash and urban flooding possible across the
Central Gulf Coast and Florida and Oklahoma into Arkansas... Potential for
isolated flooding across the Northern Plains into the Upper Midwest and the
Middle Mississippi and Ohio Valleys...

.Texas...
Locally considerable flash, urban, and river flooding will remain possible
across south-central TX through early day 2 (Tue), as additional rainfall
of 2 - 5" (locally 7 - 9") is forecast over already wet basins. Similar to
yesterday, the system generating this rainfall remains nearly stationary,
and with ample moisture and daytime heating in place, redevelopment of
heavy rainfall is likely again this afternoon. The hydrologic environment
remains highly sensitive: soils are nearly or fully saturated and
in-channel storage is limited due to lingering high flows. With isolated
moderate to major flooding ongoing or forecast along portions of the Frio,
Guadalupe, and San Saba rivers, flood waves will continue to move through
local river systems. Given these conditions, life-threatening flash and
river flooding could develop rapidly with localized heavy rainfall, and
even modest additional amounts may trigger renewed flood responses. This is
supported by the National Water Model (NWM) Short Range Forecast (SRF)
which continues to highlight the potential for rapid-onset flooding across
portions of the Hill Country, with the strongest signals occurring between
Del Rio and Killeen. However, the NWM may be underestimating hydrologic
responses and impacts on smaller streams and arroyos, especially in areas
where recent flood debris or localized morphological changes have altered
flow behavior. Impacts will be primarily driven by rainfall intensity,
especially where storms overlap areas already affected by significant
flooding in recent days.

.Mid-Atlantic into the Northeast...
Locally considerable flash, urban, and small stream flooding will be
possible through this evening across the Southside VA into the Delmarva
region, and into southern portions of the Northeast, as slow-moving storms
with intense rainfall rates continue to impact the area. Antecedent
conditions are variable, generally ranging from dry to near normal, with
pockets of wetter soils and locally elevated streamflows due to recent
rainfall. Nonetheless, a combination of urban sensitivities, slow storm
motion, and localized high rainfall rates may quickly exceed topsoil
capacity, enhancing runoff and leading to rapid rises on small streams,
creeks, and urban drainages. Locally significant flash flooding may develop
where heavier rainfall focuses over the urban corridor from Delmarva to MA,
or across the steep terrain of the Central Appalachians. While widespread
small stream or river flooding is not expected, the NWM SRF continues to
signal potential for at least isolated rapid-onset flooding. However, SRF
12-hour rapid-onset flood probabilities remain below 25%, likely due to the
model being slow to fully capture the bulk of QPF within the forecast
window. Corresponding annual exceedance probabilities (AEPs), per the High
Flow Magnitude Forecast, support the potential for locally significant
stream rises, with scattered AEPs in the 10 - 2% range occurring across the
aforementioned areas.

Additional rounds of rainfall are expected on day 2 (Tue) and through the
remainder of the forecast period across much of the region, including
further south into the Southern Appalachians and NC Piedmont, bringing a
renewed threat for flooding impacts. While confidence remains low in the
exact placement and magnitude of any hydrologic responses due to the
convective nature of the rainfall, flooding will be possible anywhere that
training or intense rainfall develops, especially in urban areas or areas
of complex terrain.

.Central Gulf Coast and Florida...
Isolated flash and urban flooding impacts are possible across southern FL
today, and along the Central Gulf Coast and much of the FL Peninsula on day
2 (Tue) through the remainder of the forecast period. Multiple rounds of
moderate to heavy rainfall are expected across the region, with 7-day
totals of 3 - 7", and locally higher amounts possible. While antecedent
conditions vary from dry to somewhat wet, flooding may be initially limited
by the presence of sandy, well-drained soils and generally dry to
near-normal streamflows. However, repeated rounds of rainfall, particularly
with training storms or high rainfall rates, could gradually overwhelm
local infiltration capacity and lead to isolated flooding. Urban corridors
along I-10 in the Central Gulf Coast and I-95 in southeast FL will also be
favorable for flash flooding due to increased impervious surfaces and poor
drainage in some areas.

.Oklahoma into Arkansas...
Isolated flash and urban flooding will also be possible from southeast OK
into northwest AR this afternoon through early day 2 (Tue), where locally
heavy rainfall rates may develop this afternoon. These areas remain
hydrologically sensitive due to rainfall over the past several days. While
widespread impacts are not expected, localized flooding could develop
quickly where storms repeatedly track over the same areas.

.Northern Plains into the Upper Midwest...
Periods of locally heavy rainfall on days 2 - 3 (Tue - Wed) may generate
isolated flooding impacts. Topsoil conditions across IA, northern IL, and
WI have recovered somewhat from previous rainfall (55 - 70% RSM, 0 - 10 cm,
NASA SPoRT), while the remainder of the region remains mostly dry. However,
streams and rivers are still running higher than normal (USGS), suggesting
the hydrologic environment remains somewhat vulnerable, particularly in
areas with flashy responses or limited channel capacity. At this time,
modest rainfall totals of up to 3" are forecast, and the placement of the
highest QPF each day does not overlap, which helps mitigate any widespread
flooding concerns. That said, additional rainfall could still lead to rapid
rises and localized flooding due to reduced in-channel storage and elevated
baseflow conditions, especially across IA.

.Middle Mississippi and Ohio Valleys...
A wet weather pattern bringing daily rounds of rainfall (generally less
than 2") today through the forecast period will increase the potential for
isolated flooding impacts. Antecedent soil conditions ahead of this first
round are wet, but not saturated, and streamflows are near normal. Combined
with the expected progressive nature of the convection, this should
initially allow for adequate infiltration. However, each subsequent round
will further increase hydrologic vulnerability, particularly in areas that
experience repeated rainfall. The greatest potential for flooding impacts
will be in areas where high rainfall rates or training storms develop,
which could quickly overwhelm current ground conditions and lead to
enhanced runoff and rising streamflows. For now, confidence in the exact
placement or magnitude of any hydrologic responses remains low given the
extended timeframe.

//Freeman



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