Subj : HVYRAIN: Excessive Rainfall Discussion
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Mon Dec 02 2024 19:09:26

FOUS30 KWBC 021909
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
209 PM EST Mon Dec 2 2024

Day 1
Valid 16Z Mon Dec 02 2024 - 12Z Tue Dec 03 2024

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

Churchill


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.

Hurley


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 creek beds 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


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/94epoints.txt__;!!DZ3fjg!_OKc-cbi77gWmkF0RWBr-1GK-BfRcaPGbrvtrw4HT_I7=
2sUNLzY8Ug5Xlyu9l4GiZwa4JjfgUMonR1InUH1ZpXXgRA0$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/98epoints.txt__;!!DZ3fjg!_OKc-cbi77gWmkF0RWBr-1GK-BfRcaPGbrvtrw4HT_I7=
2sUNLzY8Ug5Xlyu9l4GiZwa4JjfgUMonR1InUH1ZgcKQ5tA$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/99epoints.txt__;!!DZ3fjg!_OKc-cbi77gWmkF0RWBr-1GK-BfRcaPGbrvtrw4HT_I7=
2sUNLzY8Ug5Xlyu9l4GiZwa4JjfgUMonR1InUH1Z1ZKnEUQ$=20

=3D =3D =3D
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