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FOUS30 KWBC 231819
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
119 PM EST Fri Jan 23 2026

Day 1
Valid 16Z Fri Jan 23 2026 - 12Z Sat Jan 24 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL IN AND NEAR THE=20
TEXAS HILL COUNTRY & IN SOUTH FLORIDA...

South-Central TX/TX Hill Country...
Maintained low-end/5% probabilities for a conditional flash flood
risk across the Hill Country today and tonight. Overrunning showers
have developed north of a front across South-Central TX.  The 12Z=20
HREF/06z REFS guidance indicates that some convective development=20
is possible this afternoon, but a bulk of the activity is expected=20
overnight. The atmosphere becomes increasingly saturated during the
day today, and a pool of 500-1000 J/kg of MU CAPE broadens across
South TX. During the afternoon and evening, the 850 hPa inflow=20
backs and increases, which led to convective development closer to=20
the Rio Grande within the HREF ensemble suite. Enough effective
bulk shear is available for convective organization.  Adjustments=20
to the area used the 06z REFS/12z HREF 3"+ probability footprint.=20
We still have discordance between the two, with the REFS showing a=20
much higher chance of 3"+ than the HREF. Activity would be elevated
and has some chance of repeating/training before moving along.
Parts of this area have minimal topsoil, which would allow heavy
rainfall to more readily run off.


...South FL...
Activity moving south-southwest off the Gulf Stream just offshore
Palm Beach County along with attempts at a weak convective band=20
towards Key Biscayne have led to a new Marginal Risk area. Even
though 850 hPa inflow is weak, the flow enough is strong enough to
lead to ~35 kts of effective bulk shear in an environment with
500-1000 J/kg of ML CAPE and PWs of 1.5". Yesterday, radar
estimates from Key Biscayne were in the 6" range. As a precaution,
will raise a Marginal Risk for populated areas of South FL. Hourly
rain amounts up to 2" with local totals to 4" are possible. Any
heavy rain-related issues in urban areas would be isolated to=20
widely scattered.


Roth


Day 2
Valid 12Z Sat Jan 24 2026 - 12Z Sun Jan 25 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS THE
IMMEDIATE NORTHWEST GULF COAST...

Guidance trends in the 12z cycle led to further suppression of the
Marginal Risk to the immediate Middle and Upper TX coasts as well=20
as the southwest LA coast around to the mouth of the Atchafalaya=20
Basin of south-central LA. Precipitable water values, instability,
and the effective bulk shear forecast still support the idea of=20
heavy rainfall, but there's an increasing risk that it could occur
offshore. Hourly amounts to 2" with local totals to 4" remain=20
possible. Should the south to southeast model trend continue, the=20
Marginal Risk area could be dropped on later cycles.

Roth


Day 3
Valid 12Z Sun Jan 25 2026 - 12Z Mon Jan 26 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS THE
INTERIOR SOUTHEAST...

Models are in pretty good agreement concerning heavy rainfall
across interior portions of the Southeast. Precipitable water
values of ~1.25" exist within a cool atmosphere, high enough for
saturation to occur. Low-level inflow/effective bulk shear is
sufficient for convective organization. The biggest question is in
regards to MU CAPE, with NAM guidance advertising 250-500 J/kg
occurring upstream of the heavy rainfall. This should be enough to
sustain 1"+ hourly rainfall amounts, at times. A check of model=20
soundings indicate the areas of the southernmost Appalachians are=20
expected to be above freezing/as mild as the 40sF due to northward
guidance trends in the winter weather system moving by to the=20
north, which led to an extension of the Marginal Risk area across=20
northernmost Georgia into far western/southwestern NC. These areas=20
have significant relief and should be less sensitive to any recent=20
dryness. The extension into the southernmost Appalachians was=20
agreeable/coordinated with the GSP/Greer SC forecast office.

Roth

Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/94epoints.txt__;!!DZ3fjg!5I9_rXeikNmwrphPIKtkDGNDZwQetsDzuIHXCyj19VZQ=
97jO34oeq7qOGLxSyfUQSYBm25fhIuHdmbCbcJw00fhrjFU$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/98epoints.txt__;!!DZ3fjg!5I9_rXeikNmwrphPIKtkDGNDZwQetsDzuIHXCyj19VZQ=
97jO34oeq7qOGLxSyfUQSYBm25fhIuHdmbCbcJw0AbCbQaw$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/99epoints.txt__;!!DZ3fjg!5I9_rXeikNmwrphPIKtkDGNDZwQetsDzuIHXCyj19VZQ=
97jO34oeq7qOGLxSyfUQSYBm25fhIuHdmbCbcJw0CzWfEYU$=20

=3D =3D =3D
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