MESOSCALE PRECIPITATION DISCUSSION 0515
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1111 PM EDT THU SEP 24 2015
 
AREAS AFFECTED...COASTAL SC/LOWER COASTAL NC... 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 250310Z - 250840Z
 
SUMMARY...A MOISTURE LADEN AIR MASS WILL CONTINUE TO ADVANCE
TOWARD THE SC/NC COAST WITH PWATS EXPECTED TO APPROACH 2.25 INCHES
OVERNIGHT. THIS COUPLED WITH ENHANCED LOW-LEVEL CONVERGENCE ALONG
THE COASTAL FRONT SHOULD SUPPORT LOCALLY HEAVY RAINFALL CAPABLE OF
PRODUCING FLASH FLOODING. IN SPITE OF THE HIGH FFG VALUES...THE
THREAT STILL EXISTS...AT LEAST ON AN ISOLATED BASIS.

DISCUSSION...THE 03Z SURFACE ANALYSIS DEPICTED AN AREA OF LOW
PRESSURE JUST TO THE SOUTHEAST OF CHS WITH ENHANCED CONVECTION
OCCURRING IN ITS VICINITY PER CG LIGHTNING TRENDS. THE 00Z RAOB
FROM CHARLESTON SC SHOWED AN IMPRESSIVE DEEP-LAYERED MOISTURE
EXTENDING THROUGHOUT THE TROPOSPHERE WITH PWAT OF JUST ABOVE 2
INCHES. THIS IS JUST ABOVE THE 90TH PERCENTILE FOR LATE SEPTEMBER
BASED ON THE SPC SOUNDING CLIMATOLOGY. IN ADDITION TO THE MOISTURE
PROFILE...THE SAMPLED BUOYANCY WAS IMPRESSIVE WITH A TALL/SKINNY
CAPE PROFILE WITH STRONG EASTERLY LOW-LEVEL INFLOW OF  25 TO 30
KNOTS. RECENT VWP DATA SUGGESTS SUCH WINDS HAVE NOT CHANGED
SIGNIFICANTLY IN THE PAST COUPLE OF HOURS.

THE PAST COUPLE CYCLES OF THE RAP SHOW A GRADUAL INCREASE IN THE
MOISTURE/INSTABILITY ALONG THE SC/NC COAST. THIS SHOULD HELP
FOSTER ANOTHER SURGE OF HEAVY RAINFALL DURING THE OVERNIGHT HOURS
WITH MODELS HONING IN ON THE NC/SC BORDER REGION. HOWEVER...THE
SHORT TERM THREAT IS FOCUSED ACROSS THE CHARLESTON SC CWA WHERE
DUAL-POL HOURLY RATES ARE IN THE 1 TO 1.50 INCH RANGE. EXPECT THIS
ACTIVITY TO CONTINUE ADVANCING INLAND GIVEN THE PERSISTENT SURFACE
TO 750-MB EASTERLY FLOW. PLEASE SEE THE LATEST SPENES FROM
SAB/NESDIS FOR A SATELLITE PERSPECTIVE OF THIS ONGOING EVENT.
   

RUBIN-OSTER

ATTN...WFO...CAE...CHS...ILM...MHX...RAH...

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

LAT...LON   34927756 34757671 34127671 33637781 33027895 
            31878019 32348103 33118055 34267915