Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
325 AM EST Thu Dec 4 2025

Day 1
Valid 12Z Thu Dec 04 2025 - 12Z Fri Dec 05 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR THE CENTRAL
GULF COAST...

Upglide/warm-advective elevated convective activity is ongoing this
morning across portions of the central Gulf Coast with localized
hourly totals topping out near an inch or so (per MRMS estimates).
Right entrance ascent to 150-170 kt jet centered over the Ohio
Valley will keep isentropic moisture flux across the surface front
that will remain oriented along and south of the coast. A weak
mid-level shortwave will slide from west to east along the
southern periphery of the jet streak maintaining 20-25kt of west-
southwesterly 850mb flow which given ~1.75" PWs and the potential
for lingering marginal instability (MU CAPE up to 1000 J/kg now,
but forecast to decrease below 500 J/kg later this morning) may
maintain elevated convective development into midday. Internal
training of back-building convective elements will present the
greatest potential for higher rainfall totals across the Bayous of
south-central LA.

Hi-Res CAMs are in general good agreement with the heaviest
rainfall along and south of I-10 (where 3" exceedance probs from
both the 00z HREF and experimental REFS are contained). Little
change in the inherited MRGL risk, which will likely be pulled
around midday as convective activity wraps up.

Churchill/Gallina


Day 2
Valid 12Z Fri Dec 05 2025 - 12Z Sat Dec 06 2025

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

Churchill


Day 3
Valid 12Z Sat Dec 06 2025 - 12Z Sun Dec 07 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE CENTRAL GULF COAST THROUGH NORTHERN FLORIDA/SOUTHERN GEORGIA
AND FAR SOUTHERN SOUTH CAROLINA...

A quasi-stationary front draped near the FL Panhandle may become
convectively active by Day 3 (particularly late Saturday night into
Sunday morning) with the potential for localized training along the
boundary with nearly unidirectional westerly flow aloft. Maintained
an inherited MRGL risk with instability being the primary limiting
factor, but both global ensembles (GEFS and ECENS) suggest decent
odds of 2" exceedance (which may translate to localized totals as
high as 3-4" with the addition of CAMs in the coming days).

Churchill


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