Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
752 PM EST Thu Jan 8 2026

Day 1
Valid 01Z Fri Jan 09 2026 - 12Z Fri Jan 09 2026

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

...0100 UTC Update...
Two relatively targeted Marginal Risk areas (parts of the Midwest
and Lower MS Valley) remain generally on track for the overnight
hours. Both are considered 'low-end' Marginals, i.e. with the 40km
neighborhood probability of rainfall exceeding 1 or 3 hourly FFG is
closer to 5% than 15%. Deep-layer instability (or lack thereof),
even elevated, is the main inhibitor to flash flooding across the
Midwest Marginal Risk area, although some snowmelt and otherwise
low FFG values would offset somewhat. Farther south near the Gulf
Coast, there at least 250-500 J/Kg of MUCAPE would be available,
perhaps closer to 1000 J/Kg closer to the Gulf Coast. However, as
is the typical tradeoff this time of year, the soils farther south
(no snow cover nor frost depth) can absorb quite a bit more
rainfall before any runoff is generated.

Hurley

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...

20Z Update...
Following the general trend of the 12Z guidance, the outlook areas
extending from the lower Mississippi Valley to the southern
Appalachians were shifted a little south and east. A Slight Risk
was maintained from southeastern Louisiana to the southern
Appalachians, where neighborhood probabilities from the 12Z HREF
for amounts above 2 inches are 50 percent or greater. Within this
area, the HREF suggests the heaviest totals are most likely to
center from southeastern Louisiana to central Alabama, where high
(greater than 70 percent) probabilities for amounts over 3 inches,
and some 30-60 percent probabilities for amounts greater than 5
inches, are indicated.

Pereira

Previous Discussion...
...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...

20Z Update...
No significant changes were made to the Marginal Risk area
centered over the southern Appalachians.

Pereira

Previous Discussion...
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: www.wpc.ncep.noaa.gov/qpf/94epoints.txt
Day 2 threat area: www.wpc.ncep.noaa.gov/qpf/98epoints.txt
Day 3 threat area: www.wpc.ncep.noaa.gov/qpf/99epoints.txt