Subj : HVYRAIN: Excessive Rainfall Discussion
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Sun Nov 27 2022 08:06:00

FOUS30 KWBC 270805
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
305 AM EST Sun Nov 27 2022

Day 1
Valid 12Z Sun Nov 27 2022 - 12Z Mon Nov 28 2022

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

Taylor



Day 2
Valid 12Z Mon Nov 28 2022 - 12Z Tue Nov 29 2022

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

Wegman


Day 3
Valid 12Z Tue Nov 29 2022 - 12Z Wed Nov 30 2022

....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
MISSISSIPPI AND ALABAMA...

A strong shortwave trough ejecting out into the Plains Tuesday
will induce deepening cyclogenesis over the Upper Midwest with an
associated cold front progressing across portions of the lower
Mississippi Valley. Favorable right entrance region jet dynamics
of a 120 kt jet positioned over the southern Plains will help
bring widespread forcing for ascent across the region. Southerly
flow ahead of the approaching system should surge northward
anomalously high moisture, characterized by PWs approaching 1.5"+
which is between 2-3 standard deviations above normal. Model CAPE
fields show an axis of sufficient instability lifting northward
with MUCAPE of 1000-1500 J/kg possible. This overlap of deeper
moisture and instability combined with the approaching front and
large scale lift should support scattered to numerous showers and
thunderstorms Tuesday afternoon across the Lower Mississippi
Valley then further eastward into Tuesday night across portions of
MS and AL. These storms will be capable of producing intense rain
rates of 1-2"+/hr and there is some training signal given the
southwesterly/southerly mean flow orienting somewhat parallel to
expected storm motions.

The latest model guidance shows potential for a broad area of 1-2"
with some signal for isolated 3-4"+ totals during the period.
However, there remains some spatial uncertainty, particularly the
northern extent of the deeper convection and heavy rainfall
potential. Soil moisture varies from drier than normal across the
TN and OH Valleys while further south near the Gulf Coast, above
normal precipitation over the last few days has brought the top 40
cm soil layer saturation to above 80-90 percent in places. The
Slight Risk inherited was largely unchanged and adjusted based on
the latest ensemble probabilities and trends in deterministic
guidance, and highlights the greatest risk area for isolated to
scattered instances of flash flooding.

Taylor


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/94epoints.txt__;!!DZ3fjg!65daDFbhsGj4N30Q5JPO902Y4SvZZYzhv5Lsgy6t8VyE=
jDWAscB9yHQe8c8VG0pn-CG9xS98Ps3jb5gZI-eNfgeSsnk$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/98epoints.txt__;!!DZ3fjg!65daDFbhsGj4N30Q5JPO902Y4SvZZYzhv5Lsgy6t8VyE=
jDWAscB9yHQe8c8VG0pn-CG9xS98Ps3jb5gZI-eNddO7_iQ$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/99epoints.txt__;!!DZ3fjg!65daDFbhsGj4N30Q5JPO902Y4SvZZYzhv5Lsgy6t8VyE=
jDWAscB9yHQe8c8VG0pn-CG9xS98Ps3jb5gZI-eNY1r31z4$=20


$$



=3D =3D =3D
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