Mesoscale Precipitation Discussion 0257
NWS Weather Prediction Center College Park MD
1020 PM EDT Sun May 11 2025

Areas affected...Central and Southeast GA...SC Midlands and
Lowcountry

Concerning...Heavy rainfall...Flash flooding possible

Valid 120220Z - 120820Z

SUMMARY...Additional rounds of heavy showers and thunderstorms
overnight will continue to promote concerns for scattered areas of
flash flooding heading into the overnight hours.

DISCUSSION...The latest radar and satellite imagery is showing new
rounds of heavy showers and thunderstorms lifting up across
northern FL and stretching up across areas central to southeast GA
and into far southern SC. This again is being supported by a deep
layer southerly conveyor belt of warm and moist air lifting into
the Southeast U.S. while interacting with a quasi-stationary
frontal zone draped across far southern GA and up across coastal
areas of SC.

The deep layer moisture transport remains well-defined around the
eastern flank of a deep layer trough/closed low over the lower MS
Valley/western Gulf Coast region and continues to have tropical
origins with moisture seen in CIRA-ALPW advancing north up from
Central America and the western Caribbean Sea across the eastern
Gulf Coast/FL Peninsula and into the Southeast U.S. coastal plain.
00Z RAOB data shows PWs generally near or a little above 1.75
inches which is 2 to 2.5 standard deviations above normal.

This moisture transport and warm air advection will continue to
support strong isentropic ascent across eastern GA and the SC
Lowcountry going into the overnight hours which coupled with the
frontal convergence and pooling of instability along it will favor
additional concentrated areas of convection with heavy rainfall
rates.

MLCAPE values across coastal areas of GA and the SC Lowcountry are
on the order of 1000+ J/kg and are being aided by cyclonic
low-level flow off the warmer waters of the nearby Gulf Stream.
Favorable shear parameters are in place too, and thus the
environment will be conducive for some organized convective cells
with high rainfall rates capable of reaching 1.5 to 2.5
inches/hour.

The recent runs of the HRRR/RRFS guidance and also the 18Z
HREF/12Z REFS ensemble solutions support the potential for
additional rainfall totals reaching 3 to 5 inches. This will
support a continued threat for scattered areas of flash flooding
heading into the overnight hours.

Orrison

ATTN...WFO...CAE...CHS...FFC...ILM...JAX...TAE...

ATTN...RFC...SERFC...NWC...

LAT...LON   34348071 33827990 32817999 32108053 31468104
            30578150 30468233 30788297 31638315 33048272
            34058190