Mesoscale Precipitation Discussion 0039
NWS Weather Prediction Center College Park MD
518 PM EST Sat Jan 27 2024

Areas affected...portions of the Carolina Piedmont

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

Valid 272218Z - 280418Z

Summary...Showers and thunderstorms with hourly rain totals up to
2" and local amounts around 4" could lead to isolated to widely
scattered areas of flash flooding across portions of the Carolina
Piedmont.

Discussion...A set of fronts has been stalled across the Carolinas
over the past six hours, with a surface low well to the west in TN
not able to dislodge the cold air damming signature much at all so
far.  A combination of the synoptic scale warm front and a coastal
front which moved in from the Atlantic are acting as a focus for
widely scattered showers and thunderstorms over the Piedmont of
the Carolinas.  Precipitable water values are near 1.6" per GPS
data.  ML CAPE across central SC is near 1000 J/kg.  Effective
bulk shear of 35-50 kts is helping to lead to some convective
organization, both in the form of mesocyclones and attempts at
short training bands.

The coverage of showers and thunderstorms is expected to increase
as frontogensis/moisture convergence into the region increases,
which is expected to lift the boundaries somewhat northward as the
TN low moves into KY.  Recent activity appears not to be captured
well by the mesoscale guidance, with lowers confidence in the
exact threat area -- adjusted the model signal eastward to better
align with the instability and where activity is currently ongoing
per radar imagery.  The areas that have received the most rainfall
over the past week lie generally northwest of where the
thunderstorms have occurred today, though today's convection has
likely started to saturate soils in areas of the Piedmont which
had been left out of the recent rains.  With flash flood guidance
values not far above 2"/3 hours, and hourly rain totals
approaching 2" as of late, any areas of cell training, cell
mergers, or mesocyclones could lead to flash flood guidance
exceedance.  Occurrences of flash flooding are expected to be
isolated to widely scattered.

Roth

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

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

LAT...LON   36117930 35867862 34747960 33868127 33938213
            34668212 35658080