MESOSCALE PRECIPITATION DISCUSSION 0570
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
208 AM EDT SAT OCT 10 2015
 
AREAS AFFECTED...PORTIONS OF SC 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 100607Z - 101207Z
 
SUMMARY...AN INVADING FRONTAL BOUNDARY AND NEARBY LEE TROUGH ARE
EXPECTED TO ACT AS THE FOCI FOR THUNDERSTORMS WITH HEAVY RAINFALL
DURING THE NEXT SEVERAL HOURS.  HOURLY RAIN RATES UP TO 1.75"
COULD LEAD TO FLASH FLOODING OVER SATURATED SOILS/FLOOD PLAINS.

DISCUSSION...A STRENGTHENING SHORTWAVE IS SEEN ON INFRARED
SATELLITE IMAGERY ACROSS WESTERN TN AND NORTHERN MS.  TO ITS EAST
AND SOUTHEAST, TWO STREAMS OF THE WESTERLIES WERE NOTED, WITH THE
POLAR JET UP NEAR THE OH RIVER VALLEY AND MASON-DIXON LINE WHILE
THE SUBTROPICAL JET WAS DOWN ACROSS CENTRAL GA AND SC.  LIGHT RAIN
SHOWERS HAVE BEEN FORMING/SPREADING DOWNWIND ACROSS WEST-CENTRAL
SC NEAR THE SUBTROPICAL JET OVER THE PAST FEW HOURS.  AT THE
SURFACE, A FRONTAL ZONE WAS INVADING FROM NORTHERN GA AND THE
WESTERN CAROLINAS.  PRECIPITABLE WATER VALUES OF 1.25-1.5" ARE IN
THE AREA PER GPS INFORMATION.  WINDS ARE FAIRLY UNIDIRECTIONAL OUT
OF THE WEST.  MUCAPE VALUES OF 500-1000 J/KG WERE SEEN ON RECENT
SPC MESOANALYSES NEAR THE GA/SC BORDER.

THE EXPECTATION IS FOR THE WEAK LEE TROUGH ACROSS SC AND THE
INVADING FRONTAL ZONE TO ACT AS FOCI FOR CONVECTION.  LOW-LEVEL
INFLOW IS BECOMING MORE WEST-SOUTHWESTERLY AS OF LATE, WHICH
SHOULD ALLOW THE INSTABILITY NEAR THE GA/SC BORDER TO BE TAPPED. 
DIVERGENCE ALOFT SHOULD BECOME STRONGER AS THE SHORTWAVE MOVES
ACROSS TN, CLOSER TO THE REGION.  PRECIPITABLE WATER VALUES ARE
EXPECTED TO CLIMB FURTHER TO 1.75", 1.5-2 SIGMAS ABOVE THE MEAN
FOR MID-OCTOBER.  EVEN THOUGH LOW-LEVEL INFLOW IS FAIRLY WEAK --
UNDER 20 KTS -- THE 850-400 HPA MEAN WIND SHOULD CARRY CONVECTION
IN AN EAST-NORTHEAST DIRECTION AS ~25 KTS WHICH SHOULD INCREASE
THE CLOUD BASE INFLOW AT THE STORM SCALE.  THE 0-6 KM BULK SHEAR
IS SUFFICIENT FOR ORGANIZED THUNDERSTORMS, WITH 25-35 KTS NOTED IN
RECENT RAP RUNS.  WHILE THE ENVIRONMENT FAVORS THE POSSIBILITY OF
CELL TRAINING, ALSO SHOWN WITHIN MEMBERS OF THE CAM GUIDANCE,
CONVECTIVE COVERAGE IS EXPECTED TO BE GENERALLY SCATTERED IN
NATURE AS GALVEZ-DAVISON INDICES BASED ON THE 00Z GFS ARE IN THE
25-30 RANGE WHICH SHOULD KEEP CELL TRAINING TO SHORT, TRANSIENT
BANDS.  THE CAM GUIDANCE, OUTSIDE OF RECENT HRRR/RAP RUNS, IS
QUITE AGREEABLE ON A NARROW STRIPE OF 2-4" FALLING ACROSS PORTIONS
OF SC, WHICH COULD FALL QUICKLY.  THIS DEGREE OF RAINFALL WOULD
THREATEN THE MODEST FLASH FLOOD GUIDANCE ACROSS THE AREA AND BE
NEAR THE 10 YEAR RECURRENCE INTERVAL, HINTING THAT FLASH FLOODING
IS POSSIBLE.  THE AVAILABLE MOISTURE SUPPORTS HOURLY RAIN RATES UP
TO 1.75".  CONSIDERING SATURATED SOILS AND OVERFLOWED FLOOD PLAINS
WITHIN PORTIONS OF SC, FLASH FLOODING COULD OCCUR.

ROTH

ATTN...WFO...CAE...GSP...ILM...

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

LAT...LON   34818062 34767969 34767969 34037895 33378065 
            33248183 34328280 34598207 34698136 34768091