MESOSCALE PRECIPITATION DISCUSSION 0153
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
907 AM EDT WED MAY 16 2018

AREAS AFFECTED...BLUE RIDGE MTNS AND FOOTHILLS OF NC...SC...NE GA

CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE

VALID 161306Z - 161800Z

SUMMARY...FLASH FLOODING WILL BE POSSIBLE AS HEAVY RAIN PERSISTS
THIS MORNING IN PORTIONS OF THE SOUTHERN BLUE RIDGE MOUNTAINS OF
NORTHEAST GEORGIA...UPSTATE SOUTH CAROLINA...AND WESTERN NORTH
CAROLINA. PORTIONS OF THIS AREA HAVE ALREADY RECEIVED 2-6 INCHES
OF RAIN IN THE LAST 24 HOURS PER RECENT REPORTS...AND ANOTHER
SEVERAL INCHES OF RAINFALL WILL BE POSSIBLE IN LOCALIZED AREAS.

DISCUSSION...KGSP RADAR SHOWED A PROMINENT LOW-TOPPED CONVECTIVE
RAIN BAND STRETCHING (AT 13Z) FROM NEAR HENDERSONVILLE NC... TO
WALHALLA SC... TO GAINESVILLE GA... ORIENTED IN A SW-NE FASHION.
THE RAIN BAND WAS ALSO GENERALLY MOVING AND EXPANDING TO THE
NORTHEAST...ALONG THE LOW-LEVEL (925-700MB) MEAN FLOW VECTOR. THIS
RAIN BAND WAS ALSO GENERALLY OVERLAPPING AN AREA THAT RECEIVED 2-6
INCHES OF RAIN IN THE PAST 24 HOURS PER MORNING COCORAHS
REPORTS...PARTICULARLY FROM OCONEE COUNTY SC INTO TRANSYLVANIA AND
HENDERSON COUNTIES IN NC. THUS PURELY FROM A RADAR TREND AND
ANTECEDENT RAINFALL PERSPECTIVE... FLASH FLOODING APPEARS POSSIBLE
THIS MORNING IN PORTIONS OF THE BLUE RIDGE MOUNTAINS AND ADJACENT
FOOTHILLS FROM NE GA INTO WRN NC.

ALTHOUGH AVAILABLE CONVECTIVE INSTABILITY IS NOT EXTREMELY
HIGH...RAP FORECAST SOUNDINGS DO SHOW AROUND 200-400 J/KG OF
MUCAPE WITH MOST OF THE POSITIVE BUOYANCY BELOW THE -10C LEVEL.
THIS SUGGESTS THAT CONVECTIVE RAIN BANDS WILL BE POSSIBLE BUT
LIGHTNING SHOULD BE LIMITED. ADDITIONALLY... WARM RAIN PROCESSES
SHOULD BE DOMINANT WITH VERY LITTLE ICE IN THE CLOUD LAYER. MRMS
ANALYSIS RIGHT NOW SHOWS 30 DBZ ECHO TOPS AROUND 15000 FEET (CLOSE
TO THE FREEZING LEVEL) WHICH IS ALSO A STRONG INDICATION OF WARM
RAIN PROCESSES. MRMS RAINFALL ESTIMATES SEEM TO BE LOWER THAN
OBSERVATIONS... WHICH HAVE OCCASIONALLY REPORTED RATES INTO THE
0.5 TO 1.0 IN/HR RANGE. KGSP DUAL POL RADAR ESTIMATES SEEM TO BE
MORE REASONABLE IN AREAS OF LIMITED BEAM BLOCKAGE. THESE SORT OF
RATES...IF SUSTAINED FOR SEVERAL HOURS IN AREAS THAT ARE ALREADY
SATURATED FROM PREVIOUS RAINFALL... COULD LEAD TO AREAS OF FLASH
FLOODING.

LAMERS

ATTN...WFO...FFC...GSP...MRX...RNK...

ATTN...RFC...LMRFC...OHRFC...SERFC...

LAT...LON   36588106 36388051 35488136 35028187 34418267
            34068350 34038427 34378448 34898430 35438373
            35818317 36188262 36508178