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FOUS30 KWBC 080715
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
215 AM EST Thu Jan 8 2026

Day 1
Valid 12Z Thu Jan 08 2026 - 12Z Fri Jan 09 2026

...THERE ARE MARGINAL RISKS FOR EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE MIDWEST & LOWER MISSISSIPPI VALLEY...

Midwest/Lower Mississippi Valley...
A strong shortwave preceding the incoming upper level trough is=20
expected to bring 500+ J/kg of MU CAPE into portions of the region=20
during the day on Thursday. The 00z NAM's 2000+ J/kg bulls eye in=20
KS/MO right at the beginning of the period appears unrealistic/too
high based on recent SPC mesoanalysis MU CAPE trends, though its=20
trailing instability appears more reasonable, reinforced by the 03z
RAP. The mesoscale guidance advertises small areas of a low risk=20
of 3"+ across portions of KS, MO, IL, IN, and eventually LA and MS=20
Thursday night/early Friday morning. While precipitable water=20
values are in the 1-1.25" range for northern areas and 1.5"+ range=20
for southern areas, the atmosphere should be well saturated. There=20
appears to be enough instability to realize local hourly amounts of
1.5"+ where a sufficient number of organized thunderstorms are=20
able to materialize. Right now, that appears to be the biggest=20
issue. While it has been dry lately, flash flood guidance values=20
are modest across much of the area, with 3 hour guidance closer to=20
3" for the Lower Mississippi Valley, 2.5" for portions of KS/MO,=20
and 2" for IL/IN. The guidance indicates that the heavy rainfall=20
should move through quickly, so local amounts of 2-3" within a=20
couple hours could be enough for isolated to widely scattered=20
issues, particularly in urban areas. This led to the introduction=20
of Marginal Risk areas for the areas mentioned above.

Roth


Day 2
Valid 12Z Fri Jan 09 2026 - 12Z Sat Jan 10 2026

..THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
THE TENNESSEE VALLEY AND DEEP SOUTH...

Lower Mississippi Valley/Southern Appalachians...
A positively tilted trough with minimal eastward progression due to
the parent cyclone's progression northeast will generate a broad=20
axis of ascent from the Mississippi Valley to points eastward with=20
a cold frontal progression slowly migrating east. An anomalously=20
moisture plume ahead of the trough, noteworthy for January and near
summer averages with a range of 1.50-1.75", will be accompanied by
500-1500 J/kg of MU CAPE. Ample shear for convective organization=20
is expected, with low- level convergence more or less fixed from=20
the Atchafalya Basin in LA into the southern Appalachians. The=20
guidance is wet, with local 4-7" totals forecast locally. The
guidance has shifted southwest,. which caused a southwest shift in
the risk areas.

This synoptic setup is classic for a flash flood prospect across=20
this region. Deep layer southwest flow should lead to cell=20
training, and enough effective bulk shear exists for mesocyclone=20
formation. Hourly rain amounts up to 2.5" are possible here, which=20
would overwhelm urban environments. The 00z HREF for the first half
of the period advertised a 30-35% of 5"+ near Laurel MS, which if=20
it occurred within a few hours would overwhelm non-urban=20
environments as well. At the moment, this appears to be a high end
Slight Risk, but it wouldn't be surprising if a Moderate Risk=20
was considered as we get further inside the mesoscale guidance=20
window. The eastern bounds of the Marginal Risk area were=20
coordinated with the RNK/Blacksburg VA, GSP/Greer SC, and=20
FFC/Peachtree City GA forecast offices.

Roth


Day 3
Valid 12Z Sat Jan 10 2026 - 12Z Sun Jan 11 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS=20
OF THE SOUTHERN APPALACHIANS...

Heavy rainfall early in the period is expected over what should be
at least partially saturated ground across portions of the=20
Southern Appalachians before heavy rainfall ejects into the=20
southern Mid- Atlantic States. Added a Marginal Risk as a=20
precaution for this reason; the threat not expected to persist past
18z Saturday.

Roth


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/94epoints.txt__;!!DZ3fjg!6oqSrUoWKGqc9jpeU2_TgEW-NgvCN1IJYvktPyKHPvvQ=
x1ILwtSqhYoOd1rqgw2jGqmex3DGkkCPN9ZZouSXqC5pygo$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/98epoints.txt__;!!DZ3fjg!6oqSrUoWKGqc9jpeU2_TgEW-NgvCN1IJYvktPyKHPvvQ=
x1ILwtSqhYoOd1rqgw2jGqmex3DGkkCPN9ZZouSX9Azh2_A$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/99epoints.txt__;!!DZ3fjg!6oqSrUoWKGqc9jpeU2_TgEW-NgvCN1IJYvktPyKHPvvQ=
x1ILwtSqhYoOd1rqgw2jGqmex3DGkkCPN9ZZouSXygSJeSg$=20

=3D =3D =3D
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