FOUS30 KWBC 020710
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
210 AM EST Mon Dec 2 2024

Day 1
Valid 12Z Mon Dec 02 2024 - 12Z Tue Dec 03 2024

Onshore flow across far south Texas will maintain a moist/unstable
airmass that could conditionally support heavy rainfall near the
Brownsville vicinity and adjacent coastal areas especially from the
afternoon onward. This risk is too isolated/conditional for 
inclusion of a Marginal risk area at this time but will be 
monitored through the day. The probability of rainfall exceeding 
flash flood guidance is less than 5 percent.

Cook


Day 2
Valid 12Z Tue Dec 03 2024 - 12Z Wed Dec 04 2024

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

Wegman


Day 3
Valid 12Z Wed Dec 04 2024 - 12Z Thu Dec 05 2024

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

The Marginal Risk area for portions of eastern Texas and much of
western Louisiana that was inherited was removed with this update.
A fairly robust 30-40 kt LLJ will advect Gulf moisture into much of
the Mississippi Delta region and west into eastern Texas on
Wednesday. PWATs may exceed 1.75 inches, especially along the Gulf
coast. However, this is the only ingredient that is sufficient for
flooding rains. Instability, while non-zero...will be meager,
struggling in most areas to get to 500 J/kg of MUCAPE. This will be
the primary limiting factor against flooding, as a lack of
instability should keep most of the rain as stratiform. Secondly,
much of the eastern half of the U.S., including eastern Texas and
Louisiana have been very dry lately, so stream and creekbeds are
running low. The drawn out period of mostly light rain in this
area will therefore mostly be beneficial. While embedded convective
cells could briefly cause locally heavy rain, the dry conditions
and high FFGs should mitigate any flooding. Finally, at the tail
end of the event late Wednesday night into Thursday, cold frontal
passage will push any heavy rain south and out of where the
heaviest rains are expected over central Louisiana. This too should
diminish the flooding potential.

As always, increases in the guidance for rainfall amounts in the
next couple days or greater instability could require a reissuance
of the Marginal, but for now the rainfall in the guidance likely
falls in the sub-Marginal 0-5% chance category area-wide.

Wegman

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