MESOSCALE PRECIPITATION DISCUSSION 0546
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1011 AM EDT SAT OCT 03 2015
 
AREAS AFFECTED...WESTERN NORTH CAROLINA...SOUTH CAROLINA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 031400Z - 032000Z
 
SUMMARY...SIGNIFICANT AND LIFE-THREATENING FLASH FLOODING IS
EXPECTED THROUGH THE AFTERNOON ACROSS A LARGE PORTION OF SOUTH
CAROLINA AND WESTERN NORTH CAROLINA.

DISCUSSION...THE SITUATION CONTINUES TO BE LOCALLY VERY SERIOUS
ACROSS PORTIONS OF WESTERN NORTH CAROLINA...AND ESPECIALLY THE
UPSTATE OF SOUTH CAROLINA AND EXTENDING DOWN TO COASTAL
COMMUNITIES INCLUDING METROPOLITAN CHARLESTON. A PERSISTENT AND
DEEP TROPICAL MOISTURE PLUME INVOLVING MOISTURE FROM HURRICANE
JOAQUIN NORTHEAST OF THE BAHAMAS CONTINUES TO BE CHANNELED
NORTHWESTWARD IN OFF THE ATLANTIC OCEAN...AND INLAND ACROSS THE
SOUTHEAST COASTAL PLAIN AND INTO THE SOUTHERN APPALACHIANS. THIS
IS BEING FOCUSED AROUND THE NORTHEAST FLANK OF A DEEP CLOSED LOW
OVER SOUTHEAST ALABAMA AND WITHIN A STRONGLY DIVERGENT FLOW
PATTERN ALOFT THAT IS BEING FACILITATED BY ROBUST 250 MB
RIGHT-ENTRANCE REGION JET DYNAMICS.

WHILE THE STRONGEST INSTABILITY CONTINUES TO BE FOCUSED OFFSHORE
THE SOUTHEAST COASTLINE NEAR A FRONTAL ZONE...THE STRONG JET
DYNAMICS ALOFT COUPLED WITH A VERY MOIST SOUTHEASTERLY LOW LEVEL
JET OF 40 KTS OVER THE FRONT IS ALLOWING FOR A PERSISTENT BAND OF
HEAVY RAIN WITH SOME EMBEDDED THUNDERSTORMS. PWATS AS PER
GOES-SOUNDER AND GPS-DERIVED DATA IS PEAKING AROUND 2.4 INCHES
ACROSS THE SOUTH CAROLINA COASTAL PLAIN...AND THIS IS FOSTERING
INTENSE RAINFALL RATES IN SOME OF THE STRONGER CONVECTIVE ELEMENTS
TO REACH 1.5 TO 2 INCHES/HR. ON THE LARGER SCALE...THE RAINFALL
RATES HAVE TENDED TO BE CLOSER TO 1 INCH/HR OR LESS...BUT THE
PERSISTENCE OF THE RAINFALL BAND IS LEADING TO VERY SIGNIFICANT
RAINFALL TOTALS FOR THE EVENT...AND THIS WILL CONTINUE THROUGH
MID-AFTERNOON.

THE HIRES AND GLOBAL MODEL GUIDANCE IS BASICALLY UNANIMOUS IN
DEPICTING HIGH IMPACT RAINFALL TOTALS THAT WILL LIKELY LEAD TO
LOCALLY CATASTROPHIC AND LIFE-THREATENING FLASH FLOODING AND
RUNOFF PROBLEMS. EXPECT ADDITIONAL TOTALS THROUGH MID-AFTERNOON TO
BE ON THE ORDER OF 3 TO 5 INCHES...WITH ISOLATED HEAVIER AMOUNTS.
THIS WILL RESULT IN STORM TOTALS FOR SOME AREAS...ESPECIALLY IN
CENTRAL AND SOUTHEAST SOUTH CAROLINA TO ALREADY EXCEED 12
INCHES...WITH MORE RAIN EXPECTED WELL BEYOND THIS PERIOD. 

THE GUIDANCE INDICATES A GRADUAL SOUTHWESTWARD PIVOTING OF THE
DEEP MOISTURE PLUME/RAINFALL AXIS THIS AFTERNOON WHICH WILL
INCREASE THE RAINFALL AND FLASH FLOODING CONCERNS FOR THE UPSTATE
AREAS OF SOUTH CAROLINA AND ALSO SOUTHWEST NORTH CAROLINA WHERE
VERY STRONG UPSLOPE FLOW IS BEING FORECAST BY THE MODELS. IN
FACT...THE 00Z GFS PEGGED THIS REGION TO SEE 850MB/700MB MOISTURE
FLUX ANOMALIES IN EXCESS OF 5 STANDARD DEVIATIONS ABOVE NORMAL AT
18Z. THUS...EXPECT SIGNIFICANT RAINS TO DEVELOP AND OVERSPREAD
THIS REGION OVER THE NEXT SEVERAL HOURS.

ORRISON  

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

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

LAT...LON   36488163 36348038 34768012 34097998 32727929 
            32157948 31958025 32638102 33528180 34408275 
            35108339 35798298