Mesoscale Precipitation Discussion 0537
NWS Weather Prediction Center College Park MD
1233 AM EDT Wed Jul 25 2018

Areas affected...Coastal Plain of SC & NC

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

Valid 250433Z - 251033Z

Summary...Showers and thunderstorms are on the upswing across the
coastal plains of SC and southeast NC.  Hourly totals to 2" with
local amounts to 5" are possible through 11z.

Discussion...A trough/zone of surface wind convergence is acting
as a focus for a convective uptick near the SC and southern NC
coast.  Additional activity is moving into the coast from
offshore.  This is occurring in a divergent area aloft northeast
of a deep layer low just west of the Savannah River.  Precipitable
water values of 1.8-2.1" lie here per 00z sounding information. 
Inflow at 850 hPa is south-southwest at 15-25 kts (near the
magnitude of the mean 850-400 hPa wind), importing ML CAPE values
of 1000-2000 J/kg into the region.  CIN appears minimal.

The guidance shows an increase in convective activity up the coast
of NC through the Outer Banks through 10z.  With time, inflow at
850 hPa becomes more southwesterly parallel to the surface trough.
 Hourly rain totals to 2" should be possible given the available
moisture and instability.  The mesoscale guidance has a fairly
unified signal for local amounts in the 4-5" range in this area,
which has received heavy rainfall in preceding days.  Since we're
dealing with heavy rainfall expectations near the coast, there's a
non-zero chance that convection could shift offshore at some
point, forward propagating into the greater instability. 
Confidence is below average due to this possibility.

Roth

ATTN...WFO...CAE...CHS...ILM...MHX...RAH...

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

LAT...LON   36037564 35357539 35237544 35077589 34707637
            34547653 34647675 34417737 34147776 33837789
            33677870 33147912 32577998 31988082 32178110
            33218043 34777845 35497720