MESOSCALE PRECIPITATION DISCUSSION 0780
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
800 PM EDT FRI SEP 01 2017

AREAS AFFECTED...EASTERN NORTH CAROLINA

CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE

VALID 020015Z - 020530Z

SUMMARY...LARGER SCALE OVERTURNING IS COMMENCING AS
SUPERCELLS/SEVERE STORMS TRANSITION TO LARGER SCALE COMPLEX WITH
CONTINUED FLASH FLOODING THREAT THROUGH THE EARLY OVERNIGHT HOURS.

DISCUSSION...23Z SFC ANALYSIS DEPICTS A COMPLEX FRONTAL STRUCTURE
ACROSS THE CAROLINAS IN PROXIMITY TO THE DISTANT WARM CONVEYOR
BELT ASSOCIATED WITH EXTRATROPICAL CYCLONE HARVEY...PLEASE SEE
ASSOCIATED GRAPHIC FOR BOUNDARY PLACEMENT DETAILS.  A NNE TO SSW
LINE OF CONVECTION NEARLY COINCIDENTAL WITH I-95 IS FILLING IN
FROM A MESO-LOW JUST NW OF GSB TO MEB...AN OLDER WARM FRONT DRAPES
SE FROM THE LOW TOWARD OAJ THOUGH IS DYING OFFSHORE IN FAVOR OF
STRENGTHENING FRONT ALONG GULF-STREAM BOUNDARY.  IN THE WARM
SECTOR VERY UNSTABLE/MOIST AIR IS REPRESENTED BY LOWER 80S TEMPS
WITH UPPER 70S AND SOME 80S TDS SUPPORTING 2500 MLCAPES WHICH WILL
CONTINUE TO BE ADVECTED AND GENERALLY CONFLUENT WITH STRENGTHENING
SSWLY LLJ AND DEEPEST MOISTURE AXIS (TPWS TO 2.1") ALONG THE MESO
COLD FRONT AND SOUTHWARD DRAPING TROF ACROSS NE SC.

RIGHT ENTRANCE TO BROAD 70-90KT WSW TO ENE ORIENTED POLAR JET
PROVIDES EXCELLENT UPPER LEVEL EVACUATION/BROAD SCALE ASCENT FOR
THE CONVECTION TO GROW UPSCALE.  SOUTH OF THE POLAR JET...MEAN
CLOUD BEARING FLOW IS STRONG OUT OF THE SW BUT DUE TO INFLUENCE
NORTH OF THE FRONT/ENTRANCE OF THE JET BACKS MORE
EASTERLY...ENHANCING CONVERGENCE IN THE SHORTWAVE RIDGE AXIS OF
THE LARGER PARENT CIRCULATION OF HARVEY THAT BISECTS THE NC SE
COAST TO SE WV (PER GOES-WV AND 5H ANALYSIS).  GIVEN CELLS ALONG
THE EFFECTIVE COLD FRONT/COASTAL TROF ARE BECOMING ORIENTED
FAVORABLY TO THE MEAN FLOW...SOME TRAINING IS EXPECTED OVER SE NC
OVER THE NEXT FEW HOURS BEFORE ASCENDING NE ACROSS THE BOUNDARY
INTO THE EXPANDING MODERATE TO HVY PRECIPITATION SHIELD ACROSS SE
VA/NE NC.  CONVECTION WILL SUPPORT RATES OF 2.0-2.5"/HR LEADING TO
2-4" TOTALS WITHIN THE WARM SECTOR.  NORTH OF THE BOUNDARY
EMBEDDED ELEVATED CONVECTIVE ELEMENTS WITH 1.5"/HR RATES FOR
SLIGHTLY LONGER DURATION MAY SUPPORT EQUAL VALUES AND BOTH POSE
POSSIBLE FLASH FLOODING RISKS ALONG THE COASTAL PLAIN.

CELLS FURTHER WEST NEAR CLT CURRENTLY IN A FAVORABLE ENVIRONMENT
WITH SHORT-TERM FLASH FLOODING POSSIBLE IN THE VERY NEAR TERM WITH
UPPER LEVEL SUPPORT.  LOSS OF DAY TIME HEATING AND BEING WEST OF
THE WARM CONVEYOR BELT SHOULD STEADILY REDUCE CONVECTIVE VIGOR IN
THE NEXT FEW HOURS.  FF SEEMS LESS LIKELY FOR THESE CELLS WITH
EXCEPTION OF "LUCKY" CORES THAT MAY TRACK OVER AREAS AFFECTED BY
PRIOR LINE EARLIER THIS EVENING. 

GALLINA

ATTN...WFO...AKQ...ILM...MHX...RAH...

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

LAT...LON   36427683 36417610 36017551 34847661 34627783
            34617925 35077922 36157840