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FOUS30 KWBC 081530
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
1030 AM EST Thu Jan 8 2026

Day 1
Valid 16Z Thu Jan 08 2026 - 12Z Fri Jan 09 2026

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

...16Z Outlook Update...
The ongoing forecast philosophy is generally on track. Minor
changes were made to the central Plains Marginal area to trim=20
behind an ongoing convective complex in that area. This complex is
moving quickly northeastward this morning, and flash flood
potential behind it has decreased substantially.

See the previous discussion below for more information.

Cook

...Previous Discussion...

Midwest/Lower Mississippi Valley...
A strong shortwave preceding the incoming upper level trough is
expected to bring 500+ J/kg of MU CAPE into portions of the region
during the day on Thursday. The 00z NAM's 2000+ J/kg bulls eye in
KS/MO right at the beginning of the period appears unrealistic/too
high based on recent SPC mesoanalysis MU CAPE trends, though its
trailing instability appears more reasonable, reinforced by the 03z
RAP. The mesoscale guidance advertises small areas of a low risk
of 3"+ across portions of KS, MO, IL, IN, and eventually LA and MS
Thursday night/early Friday morning. While precipitable water
values are in the 1-1.25" range for northern areas and 1.5"+ range
for southern areas, the atmosphere should be well saturated. There
appears to be enough instability to realize local hourly amounts of
1.5"+ where a sufficient number of organized thunderstorms are
able to materialize. Right now, that appears to be the biggest
issue. While it has been dry lately, flash flood guidance values
are modest across much of the area, with 3 hour guidance closer to
3" for the Lower Mississippi Valley, 2.5" for portions of KS/MO,
and 2" for IL/IN. The guidance indicates that the heavy rainfall
should move through quickly, so local amounts of 2-3" within a
couple hours could be enough for isolated to widely scattered
issues, particularly in urban areas. This led to the introduction
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
axis of ascent from the Mississippi Valley to points eastward with
a cold frontal progression slowly migrating east. An anomalously
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
is expected, with low- level convergence more or less fixed from
the Atchafalya Basin in LA into the southern Appalachians. The
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
this region. Deep layer southwest flow should lead to cell
training, and enough effective bulk shear exists for mesocyclone
formation. Hourly rain amounts up to 2.5" are possible here, which
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
it occurred within a few hours would overwhelm non-urban
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
was considered as we get further inside the mesoscale guidance
window. The eastern bounds of the Marginal Risk area were
coordinated with the RNK/Blacksburg VA, GSP/Greer SC, and
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
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
Southern Appalachians before heavy rainfall ejects into the
southern Mid- Atlantic States. Added a Marginal Risk as a
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!4TZj8D8QbdcgwZDzvEI-GDXRS3OJz112P7i0earWxdQz=
N5qKTImG1pa2l3CYkPnuuBMeipJ7ah8AzoEmjtIWldpkg34$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/98epoints.txt__;!!DZ3fjg!4TZj8D8QbdcgwZDzvEI-GDXRS3OJz112P7i0earWxdQz=
N5qKTImG1pa2l3CYkPnuuBMeipJ7ah8AzoEmjtIW6mm4bwk$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/99epoints.txt__;!!DZ3fjg!4TZj8D8QbdcgwZDzvEI-GDXRS3OJz112P7i0earWxdQz=
N5qKTImG1pa2l3CYkPnuuBMeipJ7ah8AzoEmjtIWkJ4BYyY$=20

=3D =3D =3D
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