Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
855 PM EDT Sun May 11 2025
Day 1
Valid 01Z Mon May 12 2025 - 12Z Mon May 12 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE SOUTHEAST...

Isolated to scattered flash flooding will remain a concern
overnight across portions of southeast GA and southern SC. Some of
this area has already seen training convection and some flash
flooding earlier today, and additional convection is streaming
northward back into the region. The latest SPC mesoanalysis depicts
an area of instability offshore, and with easterly low level flow,
this will likely advect inland and help sustain convection across
these areas. Expect periodic backbuilding/training to persist, and
some additional flash flooding is likely. The REFS has been
favoring this corridor for heavy rainfall with both its 12z and
18z run, but the HREF and recent HRRR runs have not been as
aggressive. However the 23z HRRR run did make a pretty significant
jump towards a wetter scenario...and based on observational
trends...it does appear like something closer to the wetter
guidance may indeed pan out. Opted against a MDT risk given some
lingering uncertainty on the location and coverage of higher
amounts, along with much of the coastal plain having high FFG...but
do now consider this a higher end Slight risk and localized higher
end impacts are possible.

We also maintained a Slight risk across portions of central AL
into northern MS. Convection to the east of the deep layered low
will continue to pose an isolated to scattered flash flood risk.
Some recent indications that an uptick in activity may be starting
to occur across portions of central AL. Guidance indicates some
maintenance of this convection through the evening hours, so do
anticipate some increase in the flash flood potential.

A Marginal risk covers much of FL. Convective evolution is less
certain here...but do expect to see scattered to numerous showers
and thunderstorms. The combination of low confidence in model
solutions over FL and the high FFG keeps the risk at Marginal. It
is possible that none of the convection organizes enough or trains
long enough to cause flash flooding overnight...but can not rule
out some training segments hanging up and resulting in isolated
flash flood concerns.

Chenard


Day 1 threat area: www.wpc.ncep.noaa.gov/qpf/94epoints.txt