MESOSCALE PRECIPITATION DISCUSSION 0424
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
408 PM EDT SAT JUL 01 2017

AREAS AFFECTED...FAR SOUTHERN KY...CENTRAL/EASTERN TN...WESTERN
NC...NORTHWEST GA...FAR NORTHEAST AL

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

VALID 012005Z - 020015Z

SUMMARY...RELATIVELY SLOW-MOVING CLUSTERS OF SHOWERS AND
THUNDERSTORMS WITH INTENSE RAINFALL RATES MAY RESULT IN SOME FLASH
FLOODING THROUGH LATE AFTERNOON.

DISCUSSION...EXPERIMENTAL GOES-16 10.3 MICRON/IR IMAGERY SHOWS A
CONTINUED COOLING OF CONVECTIVE TOPS OVER AREAS OF SOUTHEAST TN
AND GENERALLY NEAR AND JUST SOUTHEAST OF THE CUMBERLAND PLATEAU AS
DIURNAL HEATING AND A MOISTURE-RICH BOUNDARY LAYER CONTRIBUTES TO
A MODERATELY UNSTABLE AIRMASS CHARACTERIZED BY MLCAPE VALUES OF
2000 TO 2500 J/KG. PWATS OF 1.7 TO 1.9 INCHES ARE IN PLACE AND
THIS WILL CONTRIBUTE TO ENHANCED RAINFALL RATES THAT MAY APPROACH
2.5 INCHES/HR.

THE CONVECTION IS FOCUSING WITHIN A BROADLY CONFLUENT LOW LEVEL
FLOW REGIME AND ALSO BEING AIDED BY SOME VERY MODEST
RIGHT-ENTRANCE REGION JET DYNAMICS ASSOCIATED WITH THE SOUTHERN
TAIL OF THE UPPER TROUGH LIFTING THROUGH THE UPPER OH VALLEY AND
LOWER GREAT LAKES REGION.

THE LATEST RADAR TRENDS ALSO SHOW SOME CLUSTERS OF CONVECTION
DEVELOPING FARTHER NORTH UP ACROSS PARTS OF FAR SOUTHERN KY AND
NORTHERN TN. OVER THE NEXT FEW HOURS ALL OF THESE CLUSTERS OF
CONVECTION WILL TEND TO CONTINUE TO ORGANIZE LOOSELY WITHIN A
MOIST/UNSTABLE BOUNDARY LAYER AND ABOUT 20 TO 30 KTS OF EFFECTIVE
BULK SHEAR WHILE ADVANCING SLOWLY EAST-SOUTHEAST.

EXPECT RAINFALL TOTALS THROUGH 00Z OF 2 TO 4 INCHES TO BE POSSIBLE
ACROSS THE THREAT AREA...WITH ISOLATED HEAVIER AMOUNTS TO NEAR 5
INCHES. FFG VALUES ACROSS AREAS OF THE CUMBERLAND PLATEAU AND
ADJACENT TERRAIN OF EASTERN TN/NORTHWEST GA AND FAR WESTERN NC ARE
RELATIVELY LOW AND WITH THE INTENSE RATES...SOME
CELL-MERGERS...AND SLOW FORWARD PROPAGATION...THERE MAY BE SOME
RUNOFF PROBLEMS AND POTENTIAL FLASH FLOODING. THE PROXIMITY OF
HIGHER TERRAIN WILL FURTHER ENHANCE THE RUNOFF CONCERNS.

ORRISON

ATTN...WFO...FFC...GSP...HUN...JKL...LMK...MRX...OHX...PAH...

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

LAT...LON   37078641 37008532 36658382 36448253 35748260
            35028365 34558416 34428516 34638580 35218611
            35678654 36078785 36778781