MESOSCALE PRECIPITATION DISCUSSION 0516
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
443 AM EDT FRI SEP 25 2015
 
AREAS AFFECTED...COASTAL SC/NC... 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 250842Z - 251312Z
 
SUMMARY...ADDITIONAL HEAVY RAINFALL EXPECTED AS CONVECTIVE
COMPLEXES OFFSHORE MIGRATE INLAND. FFG VALUES BEING QUITE HIGH
WILL BE A MITIGATING FACTOR FOR A WIDESPREAD FLASH FLOOD THREAT.
HOWEVER...STRONG LOW-LEVEL EASTERLY INFLOW IN CONJUNCTION WITH
ANOMALOUS MOISTURE IN PLACE WILL AT LEAST MAINTAIN THE CONTINUED
HEAVY RAINFALL THREAT INTO THE MORNING HOURS.

DISCUSSION...INFRARED SATELLITE IMAGERY EARLY THIS MORNING SHOWED
A PAIR OF THUNDERSTORM COMPLEXES WITH CLOUD TOPS RAPIDLY
COOLING...SOME OF WHICH HAVE EXHIBITED OVERSHOOTING TOPS. BOTH
HAVE TENDED TO FOCUS ALONG AND NORTHWEST OF A COASTAL FRONT WHICH
CONTINUES TO ANCHOR ALONG THE OFFSHORE WATERS. STRONG DEEP-LAYERED
MOISTURE FLUX CONVERGENCE WAS NOTED ALONG THIS BAROCLINIC ZONE PER
THE 08Z RAP OBJECTIVE ANALYSIS. THIS ENHANCED AXIS OF CONVERGENCE
IS EXPECTED TO GRADUALLY TRACK CLOSER TO THE COASTLINE WHICH WILL
ALLOW SOME OF THESE ENHANCED CLOUD TOPS TO MOVE INLAND. DUAL-POL
ESTIMATES SUGGEST HOURLY RATES IN THE 1 TO 1.50 INCH RANGE. WHILE
THIS IS WELL BELOW THE LOCAL FFG VALUES...REPEAT CONVECTION IS
LIKELY AS FLARE-UPS CONTINUE OVER THE UNSTABLE AIR OFFSHORE. IT
REMAINS TO BE SEEN IF THIS MORE BUOYANT AIR CAN WORK ITS WAY
TOWARD THE COAST. THIS IS A RATHER SHARP GRADIENT BASED ON THE RAP
ANALYSIS.

THE SETUP CONTINUES TO BE SUFFICIENT FOR HEAVY RAINFALL GIVEN
STRONG LOW-LEVEL CONVERGENCE ALONG THE BOUNDARY COUPLED WITH
ANOMALOUS PWATS AND A  FAVORABLE DIFFULENCE SIGNATURE ALOFT.
RECENT CAMS SUPPORT DEEP CONVECTION...PRIMARILY ALONG THE
COASTLINE WITH UNCERTAINTIES REGARDING HOW FAR INLAND THIS
ACTIVITY MAY SPREAD. IT MAKES SENSE TO KEEP THE MPD AREA ALONG THE
COAST WHERE THE BETTER SURFACE CONVERGENCE IS LIKELY TO SET UP.
WILL ALLOW THE DAY SHIFT TO REASSESS THE SITUATION UPON MPD
EXPIRATION.


RUBIN-OSTER

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

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

LAT...LON   35837661 35737569 35367541 34817561 34467652 
            33877765 33237866 32977920 33017995 33458022 
            33908015 34167936 34457867 34717830 35347729