MESOSCALE PRECIPITATION DISCUSSION 0219
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
758 PM EDT MON MAY 28 2018

AREAS AFFECTED...FAR NORTHEAST AL...CENTRAL/NORTHERN
GA...CENTRAL/WESTERN SC...SOUTHWEST NC

CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY

VALID 282355Z - 290555Z

SUMMARY...HEAVY SHOWERS AND THUNDERSTORMS TO BECOME MORE FOCUSED
THROUGH THE LATE EVENING HOURS...WITH ENHANCED RAINFALL RATES THAT
MAY EXCEED 2 INCHES/HR. FLASH FLOODING IS LIKELY.

DISCUSSION...THE LATE-DAY GOES-16 VISIBLE SATELLITE IMAGERY SHOWS
NUMEROUS CLUSTERS OF HEAVY SHOWERS AND THUNDERSTORMS SETTING UP
ACROSS CENTRAL AND NORTHEAST GA WITH ADDITIONAL CELL DEVELOPMENT
NOTED OVER PORTIONS OF NORTHWEST SC. THE ACTIVITY IS ALL
ASSOCIATED WITH THE CIRCULATION AROUND THE OUTER NORTHEAST FLANK
OF SUBTROPICAL STORM ALBERTO.

CONVECTION ACROSS THIS REGION IS BECOMING A BIT MORE FOCUSED GIVEN
ENHANCED LOW LEVEL MOISTURE TRANSPORT/CONVERGENCE AND COUPLED WITH
A 250 MB JET DIVERGENCE MAX ORIENTED FROM EASTERN GA NORTH UP
ACROSS THE FAR SOUTHERN APPALACHIANS. THERE IS A MODERATELY
UNSTABLE BOUNDARY LAYER IN PLACE WITH MLCAPE VALUES OF 1000 TO
1500+ J/KG ACROSS MUCH OF NORTHERN GA AND STRETCHING EAST ACROSS
CENTRAL/WESTERN SC.

THE PWAT ENVIRONMENT REMAINS IMPRESSIVELY CONDUCIVE FOR ENHANCED
RAINFALL RATES WITH VALUES OF 1.9 TO 2.1 INCHES...AND A NOTABLE
CONCENTRATION ALOFT IN THE 500/300 MB LAYER. THIS WILL FAVOR
HIGHLY EFFICIENT RAINFALL PROCESSES THAT WILL BE CONDUCIVE FOR
RAINFALL RATES OF 2 TO 3 INCHES/HR WITHIN THE STRONGER CONVECTIVE
CORES/SEGMENTS.

THE TRENDS OVER THE LAST FEW HOURS IN THE HRRR AND HRRRX GUIDANCE
HAS BEEN TO SUGGEST A MORE ORGANIZED CONVECTIVE EVOLUTION THROUGH
LATE EVENING...WITH AN INCREASED THREAT OF FOCUSED HEAVY/EXCESSIVE
RAINFALL NEAR THE SOUTHERN APPALACHIANS.

RAINFALL AMOUNTS OF AS MUCH AS 3 TO 6 INCHES WILL BE POSSIBLE WITH
ISOLATED HEAVIER AMOUNTS GOING THROUGH 06Z. IN ADDITION TO THE
MORE URBANIZED AREAS...THE CONCERN WILL BE THE DEEPER LAYER MOIST
SOUTHEAST FLOW INTO THE UPSLOPE AREAS OF NORTHEAST GA...UPSTATE
SC...AND SOUTHWEST NC WHERE OROGRAPHIC FORCING OVER THE TERRAIN
WILL BE ENHANCED AND THUS PROMOTING HEAVIER RAINFALL POTENTIAL.

FLASH FLOODING WILL BE LIKELY ACROSS MANY AREAS THIS EVENING ND
ESPECIALLY NEAR THE UPSLOPE AREAS OF THE SOUTHERN APPALACHIANS AS
THESE CONVECTIVE BANDS ASSOCIATED WITH SUBTROPICAL STORM ALBERTO
CONTINUE NORTH.

ORRISON

ATTN...WFO...BMX...CAE...CHS...FFC...GSP...HUN...MRX...

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

LAT...LON   35548318 35288217 34768159 33928126 33088115
            32408135 32128201 32168291 32708369 33118418
            33458488 33988590 34548583 34788565 34938516
            35058424 35408380