MESOSCALE PRECIPITATION DISCUSSION 0093
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1130 AM EDT THU JUN 06 2013
 
AREAS AFFECTED...CENTRAL AND NORTHEAST FL...SOUTHERN GA...SOUTHERN
SC 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 061530Z - 061930Z
 
SUMMARY...TROPICAL STORM ANDREA CONTINUES TO MOVE NORTHEAST
TOWARDS NORTHERN FL AND SOUTHERN GA, WHICH COULD CAUSE FLASH
FLOODING ANYWHERE BETWEEN CENTRAL FL AND FAR SOUTHERN SC OVER THE
NEXT SEVERAL HOURS.

DISCUSSION...TROPICAL STORM ANDREA IS MOVING THROUGH APALACHEE BAY
TOWARDS THE NORTHWEST FL, EXPECTED TO MAKE LANDFALL BETWEEN CEDAR
KEY AND PERRY FL LATE THIS AFTERNOON.  THE HEAVIEST RAINFALL
WITHIN ITS PRIMARY RAIN BAND APPROACHING WESTERN FL APPEARS TO BE
PROPAGATING SOUTHWARD AND REMAINING OFFSHORE, WHICH WAS INDICATED
IN THE 06Z GFS CORFIDI VECTORS.  THUNDERSTORM ACTIVITY ACROSS
CENTRAL FL WAS FILLING IN DOWNWIND OF SOUTHERN FL, WHICH CONTINUES
TO BENEFIT FROM DAYTIME HEATING/HIGH VALUES OF SURFACE-BASED
INSTABILITY.  THE MESOSCALE GUIDANCE IS HAVING SIGNIFICANT
PROBLEMS WITH THEIR RAINFALL PATTERNS, WITH A COMPROMISE OF THE
12Z HRRR AND THE 00Z NAM CONEST HANDLING THE SITUATION THE LEAST
POORLY.  

A WEAK FRONTAL BOUNDARY/BAROCLINIC TROUGH EXTENDS THROUGH CENTRAL
GA INTO CENTRAL SC, WITH THE GA PORTION EXPECTED TO SHIFT
SOUTHEASTWARD JUST NORTHWEST OF ANDREA AND THE SC PORTION EXPECTED
TO LIFT NORTHWARD THROUGH NC IN ADVANCE OF THE STORM, LEAVING A
WEAK COLD AIR DAMMING/WEDGE SIGNATURE BETWEEN THE FALL LINE/I-95
AND THE SOUTHERN APPALACHIANS.  A COMBINATION OF ANDREA'S COMMA
HEAD PRECIPITATION PATTERN AND THIS WEAK FRONT IS EXPECTED TO LEAD
TO GOOD LOW- TO MID- LEVEL FRONTOGENESIS ACROSS NORTHEAST FL AND
SOUTHERN GA TODAY, WHICH SHOULD HAVE THE HIGHEST RISK OF FLASH
FLOODING THIS PERIOD, THOUGH LOCATIONS ALONG THE WESTERN FL COAST
CANNOT BE RULED OUT IN CASE SOME OF THE HEAVIER CONVECTIVE
ELEMENTS MANAGE TO MOVE ASHORE.  FLASH FLOOD GUIDANCE VALUES --
FFGS -- HAVE LOWERED ACROSS SOUTHERN AND EASTERN FL DUE TO AN
EARLIER RAINBAND WHICH MOVED OUT INTO THE WESTERN ATLANTIC, THOUGH
THEY REMAIN HIGH ELSEWHERE ACROSS FL, SOUTHERN GA, WITH SLIGHTLY
LOWER VALUES ACROSS THE COASTAL PLAIN OF SC.  PRECIPITABLE WATER
VALUES -- PWS -- ARE BETWEEN 2 AND 2.5 INCHES WHICH COULD LEAD TO
LOCAL RAINFALL AMOUNTS OF 3-5 INCHES WITHIN A COUPLE HOURS WHERE
CELLS TRAIN, WHICH WOULD CAUSE FLASH FLOODING.

ROTH

ATTN...WFO...CHS...MFL...MLB...TBW...JAX...FFC...TAE...

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

LAT...LON   29388543 31468386 32788203 32688034 31018013 28898063
            26768106 25768202 27648352 29388543