MESOSCALE PRECIPITATION DISCUSSION 0547
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
359 PM EDT SAT OCT 03 2015
 
AREAS AFFECTED...PORTIONS OF NC, SC, NORTHERN GA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 031958Z - 040158Z
 
SUMMARY...HEAVY RAINFALL WITHIN THE WARM CONVEYOR BELT OF AN
OCCLUDED CYCLONE IS EXPECTED TO LENGTHEN/WORSEN THE FLASH FLOOD
EVENT.  CATASTROPHIC FLASH FLOODING IS POSSIBLE.

DISCUSSION...HEAVY RAIN CONTINUES TO FALL WITHIN THE WARM CONVEYOR
BELT OF AN OCCLUDED CYCLONE.  WHILE CONVECTION HAS BEEN
CONCENTRATING OFFSHORE NEAR ITS TRIPLE POINT LOW, SOME COOLING HAS
BEEN NOTED ON SATELLITE IMAGERY IN THE WESTERN CAROLINAS AND
NORTHEAST GA.  OTHER THUNDERSTORMS HAVE BEEN FORMING NEAR A
COASTAL FRONT IN EASTERN NC, AIMING TOWARDS AN AREA THAT HAVE
RECENTLY RECEIVED HEAVY RAINFALL IN SOUTHERN NC.  PRECIPITABLE
WATER VALUES OF 1.7-2.1" LIE ACROSS THIS AREA, AT LEAST 1.5 SIGMAS
ABOVE THE MEAN FOR EARLY OCTOBER.  INFLOW AT 850 HPA IS 30-50 KTS,
ROUGHLY THE MAGNITUDE OF THE 850-400 HPA MEAN WIND.  RAINFALL
AMOUNTS DURING THE PAST SIX HOURS IN THIS REGION HAVE BEEN ROUGHLY
3-6", WHICH HAS A RECURRENCE INTERVAL OF 10 YEARS.  THE RAINFALL
DURING THE PAST 24 HOURS HAS GENERALLY REACHED THE 100 YEAR
RECURRENCE INTERVAL, WITH ISOLATED AREAS REACHING THE 1000 YEAR
RECURRENCE INTERVAL, AND MORE RAIN IS COMING.

THE CAM GUIDANCE INDICATES THAT ANOTHER 4-7" OF RAIN SHOULD FALL
DURING THE NEXT SIX HOURS, COMPOUNDING CURRENT FLASH FLOOD ISSUES.
 RADAR ESTIMATES ACROSS THE PIEDMONT/SOUTHERN APPALACHIANS HAVE
BEEN RUNNING ~50% TOO LOW, MASKING THE MAGNITUDE OF THE RAINFALL
ISSUES.  IN THE MOUNTAINS, MUDSLIDES AND LANDSLIDES ARE
ANTICIPATED.  IN THE LOW LANDS, FLAT SHEETS OF WATER COULD RISE IN
AREAS WHERE RAIN RATES EXCEED 2" AN HOUR, WHOSE IMPACTS WOULD BE
SIGNIFICANT IN THE URBAN AREAS OF CHARLESTON, COLUMBIA, AUGUSTA,
GREENVILLE/ SPARTANBURG, AND THE NORTHEASTERN ATLANTA SUBURBS. 
CONSIDERING THE AVAILABLE INSTABILITY AND THE EXPECTED INCREASE IN
850 HPA INFLOW IN THE SOUTHERN APPALACHIANS, RAIN RATES OF 1.5"
ARE POSSIBLE IN THE SOUTHERN APPALACHIANS WITH RATES CLOSER TO 3"
AN HOUR POSSIBLE WHERE CELLS TRAIN CLOSER TO THE COASTAL FRONT IN
NORTHEAST GA, CENTRAL SC AND SOUTHERN NC.  FLASH FLOODING IS
LIKELY, WHICH COULD BECOME CATASTROPHIC GIVEN THE SATURATED SOILS
AND ONGOING FLOODING IN THE REGION.

ROTH

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

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

LAT...LON   35898005 35637915 34957995 34237868 33867857 
            32228057 31598163 32968304 33488349 34458456 
            35258414 35808300 35618100