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FOUS30 KWBC 241554
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
1054 AM EST Sat Jan 24 2026

Day 1
Valid 16Z Sat Jan 24 2026 - 12Z Sun Jan 25 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER
CENTRAL/SOUTHERN LOUISIANA INTO SOUTHERN MISSISSIPPI...

An Arctic front, analyzed 50-100 miles south of the LA coast at=20
15Z is expected to slowly lift north today/tonight over=20
southeastern LA and southern MS with a weak surface wave or two=20
developing along the front. This will occur ahead of an eastward=20
advancing southern stream shortwave trough over the Baja Peninsula,
with anomalous moisture out ahead advecting northward from the=20
Gulf. Earlier this morning (13-14Z), observed hourly rainfall rates
along the upper Texas Coast were in the 2 to 3 inch range with 1=20
inch in 15 minutes reported in Brazoria County. This same moisture=20
plume will be advancing downstream across the central Gulf Coast=20
with precipitable water values increasing into the 1.5 to 1.9 inch=20
range.

Relatively steep 700-500 mb lapse rates of 6.5 to 7.5 C/km will=20
support elevated instability above a low-level inversion located
between 850 mb and just above the surface to support MUCAPE up to
~1000 J/kg from LA into south-central MS with parcels more surface
based as one moves closer to the Gulf Coast. While CAPE will be
marginal, sufficient shear will exist for quasi-organized cells
with motions similar to the orientation of low level convergence
axes, allowing for training potential. Hourly rainfall of 1 to 2+
inches and 24 hour storm totals of 3 to 5 inches will be possible.
A lower end Marginal Risk was introduced in coordination with the=20
affected WFOs, with impacts likely remaining focused within any=20
urban overlap of heavy rain.

Otto


Day 2
Valid 12Z Sun Jan 25 2026 - 12Z Mon Jan 26 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS THE
DEEP SOUTH AND ADJACENT SOUTHERN APPALACHIANS...

Most guidance is supportive of perhaps several rounds of moderate
rain across the Marginal Risk area, preceding a more focused
linear complex progged to move through the discussion area from
west to east in the 12Z-00Z timeframe. The combination of preceding
rainfall, moistening/destabilizing environment (via advection
processes), and locally sensitive ground conditions/urban areas are
all suggestive of isolated excessive runoff concerns. The extent
of icing/freezing conditions across the southern Appalachians are
likely to hinder runoff, but decided to keep the Marginal Risk area
there for the sake of consistency. Only changes to the ongoing
forecast are a slight expansion of Marginal southeastward into
west-central/central Alabama (southwest of Birmingham), where
modeled convective trends suggest an uptick in QPF/flash flood
potential (albeit isolated).

Cook


Day 3
Valid 12Z Mon Jan 26 2026 - 12Z Tue Jan 27 2026

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Cook


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/94epoints.txt__;!!DZ3fjg!5FN2-D-kaawlODANBPrTajyz-2p6jjFDQzOD7Znia4t9=
n0Hth7qx8ympG3gFIr68TZaT-SrlGylqz5p8BHZiVH_UbaE$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/98epoints.txt__;!!DZ3fjg!5FN2-D-kaawlODANBPrTajyz-2p6jjFDQzOD7Znia4t9=
n0Hth7qx8ympG3gFIr68TZaT-SrlGylqz5p8BHZiy5DSRUY$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/99epoints.txt__;!!DZ3fjg!5FN2-D-kaawlODANBPrTajyz-2p6jjFDQzOD7Znia4t9=
n0Hth7qx8ympG3gFIr68TZaT-SrlGylqz5p8BHZiax1cfrI$=20

=3D =3D =3D
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