203  
AWUS01 KWNH 241142  
FFGMPD  
NCZ000-SCZ000-GAZ000-241745-  
 
MESOSCALE PRECIPITATION DISCUSSION 0141  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
742 AM EDT MON APR 24 2017  
 
AREAS AFFECTED...EXT EASTERN GA...SOUTHEAST NC...SC  
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY  
 
VALID 241145Z - 241745Z  
 
SUMMARY...TRAINING CONVECTIVE BANDS WITH SOME STATIONARY NATURE  
CLOSER TO UPPER LOW/PIVOT AXIS IN NW SC/NE GA.  
 
DISCUSSION...GOES-E WV LOOP DENOTES VERY STRONG CONSOLIDATED UPPER  
LOW DIGGING INTO SE GA ATTM PROVIDING AN EXPANSIVE REGIME OF  
DIFFLUENCE/DIVERGENCE ACROSS THE CAROLINAS PROVIDING EXCELLENT  
REGIME TO SUPPORT BROAD SCALE ASCENT FOR LARGE SHIELD OF MODERATE  
PRECIPITATION BUT ALSO GOOD EVACUATION FOR EMBEDDED CONVECTIVE  
BANDS. AT THE SURFACE A 1004 LOW SITS NW OF SAVANNAH GA WITH WARM  
FRONT HUGGING THE WARM FRONT UP TO THE NC OUTERBANKS...MOISTURE  
AND INSTABILITY IS GENERALLY LIMITED TO THE WARM SECTOR THOUGH  
MODEST 20-30KT ISENTROPIC ASCENT THAT IS GENERALLY TIGHTENING IN  
CONFLUENCES HAS FOCUSED MST FLUX CONVERGENCE TO PRODUCE A LINE OF  
CONVECTION (AIDED BY THE WESTERN EDGE OF THE GULF STREAM) ACROSS E  
SC AS WELL AS A SECONDARY LINE FORMING FROM NEAR BEAUFORT TO EAST  
OF COLUMBIA. CLOUD BARING FLOW IS GENERALLY UNIDIRECTIONAL NEAR  
THE DEVELOPMENT REGION AND FANNING OUT FURTHER NORTH TO THE SC/NC  
BORDER...FOCUSING SOME TRAINING ENVIRONMENT AS THE TWO LINES ARE  
EXPECTED TO MERGE OVER THE NEXT FEW HOURS IN E SE. GIVEN  
STRENGTHENING DPVA AS WELL AS INCREASING BUT SLOWLY BACKING  
SOUTHERLY FLOW OFF THE ATLANTIC WITH SFC TDS IN THE UPPER 60S TO  
NEAR 70...CONTINUED UPSTREAM REDEVELOPMENT IS EXPECTED THROUGH THE  
MORNING. CURRENTLY GIVEN FAIRLY WARM MID-LEVELS LAPSE RATES ARE  
MILD LIMITING INSTABILITY TO LESS THAN 1500 J/KG WITH SOME DRY AIR  
PRESENT TOO LIMITING RAINFALL EFFICIENCY AS WELL WITH TPWS IN THE  
1.4-1.5" NOT FULLY TAPPING THE DEEPER TROPICAL CONNECTION EXPECTED  
LATER THIS AFTERNOON...AS SUCH RAINFALL RATES WILL NOT BE WORST  
CASE SCENARIO WITH 1HR RATES OF 1.5" MAYBE REACHING 2" IN MERGERS  
AND FOR SHORT TIME PERIODS. STILL...GIVEN THE  
ORIENTATION/PERSISTENCE THIS WILL LEAD TO THE POTENTIAL OF SPOT  
3-5" TOTALS OVER THE NEXT 6HRS PARTICULARLY FROM SE OF I-77 AND E  
OF I-26 PERHAPS AFFECTING SE NC AS WELL...THERE IS FAIRLY GOOD  
CONFIDENCE DUE TO STRONG AGREEMENT IN HI-RES CAMS IN THIS SETUP  
PRODUCING THESE MAGNITUDES OF RAINFALL THAT FLASH FLOODING IS  
CONSIDERED LIKELY THOUGH THE CAMS ARE LESS PRECISE ON THE EXPECTED  
LOCATION...IE HOW FAR EAST TOWARD NC BOARDER.  
 
FURTHER WEST...E GA/W SC. TROWAL JUST AHEAD OF MAIN HEIGHT  
FALLS/TROF DENOTED WELL IN WV CHANNELS ON GOES-16...WILL HAVE A  
MORE LIMITED ISENTROPIC ASCENT REGIME THAN FURTHER EAST...YET  
GIVEN THE TRACK OF THE UPPER LOW...THE CELL MOTIONS WILL BE FAIRLY  
WEAK AND MAY PRESENT SOME STATIONARY NATURE PARTICULARLY LATER  
THIS MORNING CLOSE TO THE AUGUSTA REGION. WHILE THE COVERAGE OF  
CONVECTION WILL BE MORE SCATTERED DUE TO THE FURTHER LIMITED  
INFLOW/INSTABILITY REGIME...FLASH FLOODING UNDER THESE STATIONARY  
CELLS IS POSSIBLE WITH TOTALS OF 1.5-3.5" POSSIBLE.  
 
ALONG THE NC COAST...GREATEST UNCERTAINTY IN HEAVY RAINFALL OVER  
THE MORNING HOURS RESIDES ALONG THE WARM FRONT ACROSS NC. STRONG  
ONSHORE FLOW AND MODEST INSTABILITY FROM GULF STREAM ENVIRONMENT  
WILL BE SUFFICIENT FOR CONVECTION TO DEVELOP...HOWEVER WITH  
LIMITED FOCUS CONVECTION MAY BE WEAKER AND MORE BROKEN REDUCING  
FLOODING CONCERN IN THE SHORT-TERM. HOWEVER...IT IS POSSIBLE WITH  
SOME FOCUSED FORCING SUCH AS THE LINE CURRENTLY APPROACHING  
WILMINGTON NC VICINITY SOME BANDED/TRAINING CONVECTIVE REGIMES MAY  
FORM AND POSE THE FLOODING CONCERNS SEEN FURTHER SW IN SC. STILL  
THE RAINFALL THROUGH THE MORNING WILL BE SUFFICIENT TO SET THE  
STAGE FOR FURTHER FLOODING CONCERNS LATER THIS AFTERNOON AS THE  
TROPICAL MOISTURE AND FORCING IS TAPPED FROM THE SYSTEM OFFSHORE.  
 
GALLINA  
   
..PLEASE SEE WWW.WPC.NCEP.NOAA.GOV FOR GRAPHIC PRODUCT
 
 
ATTN...WFO...CAE...CHS...FFC...GSP...ILM...MHX...RAH...  
 
ATTN...RFC...SERFC...  
 
LAT...LON 35267966 35237894 35247758 34927711 34427692  
33877803 33537874 33067904 32747950 32098031  
32098065 32258093 32928154 33398261 34088339  
34588349 34818242 34548169 34308119 34948083  
35138023  
 
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