Mesoscale Precipitation Discussion 0075
NWS Weather Prediction Center College Park MD
647 PM EDT Sun Mar 16 2025

Areas affected...Central SC...South-central NC...

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

Valid 162245Z - 170400Z

SUMMARY...Expanding thunderstorms within favorable repeat/training
environment pose possible isolated incidents of localized flash
flooding into early overnight period.

DISCUSSION...Regional RADAR and GOES-E VIS/EIR loops show
destabilization and convective growth across the Piedmont of
central SC starting to move into central NC.  Clear skies
throughout the day allowed for increased insolation and temps to
rise into the upper 70s, low 80s along a tight deep layer moisture
gradient.  However, surface low level confluence with
southwesterly flow intersecting with SSW 10-15kts of flow backed a
bit off the coastal Plain is providing sufficient moisture
convergence given Tds into the low to mid 60s.  That flux and
solid updraft strength is supporting 1.5"/hr rates.  Deep layer
steering does support fast cell motions, however, it is fairly
ideally aligned with the low-level convergence axis to allow for
repeating/training, though slow eastward propagation is expected,
spots of 2-2.5" totals in 1-2 hours which is close to exceeding
the FFG values mainly along the Fall-line and the axis of
saturated soils from this morning's heavy rainfall from Allendale
county to Orangeburg county to N Dillon county where 1hr FFG
values are 1.5-2" and 3hr are 1.5-2.5". 

There is some uncertainty in potential for favorable back-building
environment especially toward the GA/SC line. Stronger forcing
near the southeast base of the rounded upper-level (500 to 300 mb)
jet should support divergence aloft and weak DPVA to aid low level
inflow for back-building; however, drier air infiltrating aloft
also looks to be mixing downward and overall Pwats are decreasing
upstream suggestive of drier air mixing and increasing eastward
propagation limiting training/repeating potential. 

Gallina

ATTN...WFO...CAE...CHS...GSP...ILM...RAH...

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

LAT...LON   35777959 35627911 35257877 34747884 34347905
            33907955 33158060 32738168 33088194 34098138
            34578106 35518014