MESOSCALE PRECIPITATION DISCUSSION 0260...CORRECTED
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
521 PM EDT MON MAY 22 2017

CORRECTED FOR SENTENCE FRAGMENT AT THE END OF THE FIRST DISCUSSION
PARAGRAPH

AREAS AFFECTED...PORTIONS OF SC & SOUTHEAST NC

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

VALID 222116Z - 230316Z

SUMMARY...THUNDERSTORMS CONTINUE TO INCREASE IN COVERAGE ACROSS
THE CAROLINAS.  HOURLY RAIN RATES UP TO 2" WITH LOCAL AMOUNTS TO
4" ARE EXPECTED.

DISCUSSION...A BOUNDARY HAS BEEN SAGGING SLIGHTLY SOUTHEAST ACROSS
SC DOWNWIND OF A WEAK WAVE OF LOW PRESSURE NEAR AUGUSTA GA.  A
SHORTWAVE ALOFT ACROSS NORTHEAST GA IS APPROACHING THE UPPER
SAVANNAH RIVER AT THIS TIME.  INFLOW AT 850 HPA IS MODEST, 10-15
KTS FROM THE SOUTHWEST.  MLCAPES REMAIN IN THE 1000-2000 J/KG
RANGE.  EFFECTIVE BULK SHEAR IS 35 KTS PER SPC MESOANALYSES, WHICH
HAS LED TO SOME CONVECTIVE ORGANIZATION.  WITH THE WIND FLOW
ACROSS THE REGION FAIRLY UNIDIRECTIONAL FROM THE WEST-SOUTHWEST TO
SOUTHWEST, THERE HAVE BEEN OCCASIONAL SHORT TRAINING BANDS ACROSS
SC AND SOUTHEAST NC.

CELL MOTION TO THE EAST-NORTHEAST AT 20-25 KTS IS EXPECTED.  THE
MESOSCALE GUIDANCE HAS A GOOD SIGNAL FOR LOCAL AMOUNTS IN THE 3-4"
RANGE OVER THE NEXT SEVERAL HOURS.  SIGNALS WITHIN THE 12Z SSEO
NEIGHBORHOOD PROBABILITIES AND 12Z GFS-BASED GALVEZ-DAVISON
INSTABILITY INDEX (30-35 RANGE) REVEAL THAT CONVECTIVE COVERAGE
COULD SLIGHTLY INCREASE FURTHER AND MAINTAIN ITSELF PAST SUNSET
UNTIL AT LEAST 03Z.  HOURLY RAIN RATES UP TO 2", WITH LOCAL
AMOUNTS UP TO 4", ARE ANTICIPATED WHICH WOULD BE MOST PROBLEMATIC
IN URBAN AREAS.  MOST OF THE GUIDANCE APPEARS TO BE SOMEWHAT
NORTHWEST OF WHAT IS EXPECTED WITH THE QPF PATTERN IN THIS REGION,
FORECASTING THE BOUNDARY IN THE CAROLINAS TO LIFT BACK TO THE
NORTHWEST, WHICH SEEMS UNLIKELY AT THIS TIME AS CONVECTION SHOULD
LEAD TO A LITTLE MORE SOUTHEAST ADJUSTMENT.  CIN SHOULD DEVELOP
NEAR THE BOUNDARY AFTER SUNSET WHICH COULD LEAD TO ELEVATED
CONVECTION BEYOND 01Z.  IT APPEARS THE 12Z SPC WRF AND 12Z WRF
NSSL HAVE THE BEST GRASP OF THE EXPECTED RAINFALL PATTERN.

ROTH

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

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

LAT...LON   34987810 34507751 33837799 33417905 33417919
            33148028 33168180 33798190 34578068 34897951