Mesoscale Precipitation Discussion 0918
NWS Weather Prediction Center College Park MD
808 AM EDT Tue Aug 12 2025

Areas affected...portions of central/Upstate South Carolina and
central North Carolina

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

Valid 121208Z - 121808Z

Summary...Areas of heavier rainfall are materializing across the
discussion area and 1 inch/hr rain rates are increasing in
coverage.  These rates are falling on sensitive ground conditions
from prior rainfall.  Flash flooding is possible this morning.

Discussion...Over the past half hour, radar and satellite have
indicated an uptick in convective intensity and coverage generally
in areas from central South Carolina into southwestern North
Carolina.  This uptick in convective coverage appears to be tied
to a weak mid-level shortwave trough/vorticity max over central
South Carolina.  The showers/storms are in a marginally unstable,
but very moist environment (1.5-2 inch PW values, 1000 J/kg
SBCAPE) with weak inhibition, fostering efficient rainfall rates
with the ongoing activity.   Latest MRMS data suggests that 1
inch/hr rain rates were beginning to materialize in a few spots. 
Furthermore, these rates were falling on sensitive local ground
conditions due to prior rainfall, with FFG thresholds below 0.25
inch/hr in a few spots across the discussion area.

Models/observations are all suggestive of a gradual increase in
both coverage and intensity of convection through the morning
hours.  With weak southwesterly steering flow in place, several
areas of slow-moving convection and occasional cell mergers are
expected to develop and boost rain rates into and above the 1
inch/hr threshold at times.  These rates will pose a flash flood
risk, though the greatest risk of impacts may occur near sensitive
urban areas and locales that have experienced the highest rainfall
totals over the past 1-2 days.  Areas just west of Columbia, SC
could experience excessive runoff in the near term, with
additional locales (including urban areas near Raleigh/Durham and
Columbia) experiencing an increasing threat through 16Z/noon EDT
or so.

Cook

ATTN...WFO...CAE...GSP...ILM...MHX...RAH...RNK...

ATTN...RFC...ALR...ORN...NWC...

LAT...LON   36297879 35577734 33738053 33548204 35158286
            35978159 36268043