MESOSCALE PRECIPITATION DISCUSSION 0524
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
141 PM EDT MON JUL 23 2018

AREAS AFFECTED...CENTRAL/NORTHERN SC...CENTRAL/ WESTERN NC

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

VALID 231740Z - 232340Z

SUMMARY...SLOW-MOVING SHOWERS AND THUNDERSTORMS WILL TEND TO
EXPAND IN COVERAGE OVER THE NEXT FEW HOURS. HEAVY RAINFALL RATES
OF OVER 2 INCHES/HR WILL FOSTER SOME FLASH FLOODING CONCERNS.

DISCUSSION...THE LATEST GOES-16 AIRMASS RGB IMAGERY DEPICTS AN
UPPER LEVEL SHORTWAVE PIVOTING SLOWLY NORTHEAST UP ACROSS CENTRAL
SC AND THE COMPACT DYNAMICS ASSOCIATED WITH IT IS INTERACTING WITH
INCREASING BOUNDARY LAYER INSTABILITY VIA STRONG DIURNAL HEATING
FOR FOR SEVERAL CLUSTERS OF SHOWERS AND THUNDERSTORMS. THE
ACTIVITY IS ALSO FOCUSING WITHIN AN AREA OF 250 MB LEFT-EXIT
REGION JET DYNAMICS COURTESY OF A JET STREAK LIFTING ALONG THE
GA/SC COASTAL PLAIN...AND IN VICINITY OF A FRONT DRAPED ACROSS THE
REGION WHICH IS TENDING TO FOCUS FAVORABLE LOW LEVEL CONVERGENCE
ACROSS THE REGION.

THE CONVECTION SHOULD TEND TO EXPAND IN COVERAGE THIS AFTERNOON
AND BEGIN TO DEVELOP FARTHER NORTH ALONG THE FRONTAL ZONE ACROSS
THE SOUTHERN MID-ATLANTIC REGION. PWATS ACROSS THE REGION ARE
SLOWLY RISING GIVEN THE RETROGRESSIVE LARGE SCALE FLOW PATTERN
SEEN ALONG THE EAST COAST AND ARE CURRENTLY ON THE ORDER OF 1.5 TO
1.75 INCHES.

FFG VALUES ARE RATHER HIGH ACROSS THE REGION...BUT THE CELL
MOTIONS ARE EXPECTED TO BE VERY SLOW GIVEN THE WEAK STEERING
CURRENTS. THIS COUPLED WITH THE INCREASING PWAT ENVIRONMENT THIS
AFTERNOON SHOULD LEAD TO SOME ENHANCED RAINFALL RATES AND THE
LATEST HRRR GUIDANCE DOES FAVOR AS MUCH AS 3 TO 4 INCHES OF
RAIN...WITH ISOLATED HEAVIER AMOUNTS.

SOME FLASH FLOODING WILL BE POSSIBLE GIVEN THESE TOTALS...AND
ESPECIALLY IF ANY OF THE ACTIVITY GETS INTO MORE URBANIZED AREAS.

ORRISON

ATTN...WFO...CAE...GSP...ILM...MRX...RAH...RNK...

ATTN...RFC...LMRFC...OHRFC...SERFC...

LAT...LON   36588023 36177963 35027977 34058045 33908135
            34368206 35288234 36428171