289
AGUS74 KWCO 171527
HMDNWC

National Hydrologic Discussion - EXPERIMENTAL
NWS National Water Center - Tuscaloosa AL
1015 AM CDT THU JUL 17 2025

.Synopsis...
Potential for flooding impacts along the Central Gulf Coast and the Ohio
Valley into the Mid-Atlantic... Isolated flash flooding possible across the
Southwest into the Rockies...

.Central Gulf Coast...
There is an increasing potential for flooding impacts today thru day 2
(Fri) as tropical moisture surges into the region, bringing heavy rainfall
totals of 2 - 5", with locally higher amounts possible in southern LA.
Antecedent conditions leading into this event are dry to near normal, and
any flooding should be initially limited by the regions sandy,
well-drained soils and the ability to absorb early rounds of rainfall, as
well as by the ample storage capacity remaining in area streams and rivers.
However, repeated rounds of rainfall capable of producing very high
rainfall rates could eventually overwhelm local infiltration capacity and
lead to flooding impacts, most likely of the flash and urban variety. Urban
corridors along I-10 remain vulnerable to flash flooding due to impervious
surfaces and poor drainage in some areas. Nonetheless, there is still a lot
of uncertainty around the placement and development of the tropical
moisture, which will influence where the heaviest rainfall occurs and how
the event evolves.

.Ohio Valley into the Mid-Atlantic...
A wet weather pattern bringing daily rounds of rainfall will maintain the
potential for flooding impacts through the forecast period. Rainfall totals
of 2 - 4" are expected, with locally higher amounts possible. Antecedent
conditions are average to wet (0 - 10 cm, NASA SPoRT) across the southern
portions of the Ohio Valley into VA and PA with streamflows running normal
to much above normal (USGS). This combination suggests there is some
infiltration and storage capacity available to handle additional rainfall
depending on its location, but may be overwhelmed and lead to excess
runoff, especially where high rainfall rates or repeated storms occur.
Overall, widespread flooding is not expected, but the greatest potential
for flooding will be where storms train or become slow-moving, especially
in urban areas or complex terrain.

.Southwest into the Rockies...
Isolated flash flooding is possible through today as monsoonal moisture
increases. Localized heavy downpours may lead to flash flooding in
sensitive basins, urban areas, and burn scars. The greatest potential will
be in northeastern NM, where conditions will be most favorable for higher
rainfall totals.

//TMK





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