MESOSCALE PRECIPITATION DISCUSSION 0371
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
930 AM EDT THU JUN 28 2018

AREAS AFFECTED...SOUTH CENTRAL TN INTO NORTHERN GA

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

VALID 281330Z - 281730Z

SUMMARY...CONVECTION TRACKING ACROSS AREAS THAT SAW HEAVY RAINFALL
WEDNESDAY AFTERNOON INTO EARLY THIS MORNING COULD POSE A FLASH
FLOOD THREAT THIS MORNING

DISCUSSION...REGIONAL RADARS INDICATED CONVECTION AHEAD OF A SHORT
WAVE OVER EASTERN TN TRACKING SOUTHEAST ACROSS SOUTH CENTRAL TN
INTO NORTHERN GA THIS MORNING. THE CONVECTION IS TAPPING INTO
MUCAPE VALUES BETWEEN 1000-1500 J/KG EXTENDING ACROSS EASTERN TN
INTO NORTHERN GA (WITH 12Z SOUNDINGS AT BNA AND FFC SHOWING SBCAPE
VALUES IN EXCESS OF 2000 J/KG).

THE CONVECTION IS ROOTED IN AN AXIS OF 2.00+ INCH PRECIPITABLE
WATER AIR STRETCHING ACROSS THE SAME AREA. THE DEEP MOISTURE IS
ALLOWING THE CONVECTION TO PRODUCE HOURLY RAINFALL RATES BETWEEN
1.50/2.00 INCHES OVER ROANE COUNTY TN. DRY AIR IN THE MID LEVELS
OF THE NEARBY 12Z SOUNDINGS, AS WELL AS THE OUTPUT FROM THE KOHX
HCA PRODUCT...SUGGEST THAT HAIL COULD BE CONTAMINATING THE HOURLY
RAINFALL PRODUCTS. HOWEVER...GIVEN THE DEPTH OF THE MOISTURE IN
PLACE...HOURLY RAINFALL RATES BETWEEN 1.50/2.00 INCHES IS
PLAUSIBLE OVER SOUTH CENTRAL TN.

THE MOST RECENT HRRR/EXPERIMENTAL HRRR SHOWED THAT THE CONVECTION
TRACK SOUTHEAST WITH THE SHORT WAVE...CROSSING SOUTH CENTRAL TN
BEFORE 28/15Z...AND CONTINUING ACROSS NORTH GA THROUGH ABOUT
28/17Z. THESE SOLUTIONS SHOWED LOCAL 2.00/3.00 INCH RAINFALL
AMOUNTS IN AREAS WHERE LOCAL RADARS AND THE MRMS 24 HOUR RAINFALL
PRODUCTS SHOWED AS MUCH AS 3.00 TO 5.00 INCHES OF RAINFALL...WITH
THE HIGHEST AMOUNTS OVER TN. THE ADDITIONAL RAINFALL COULD
INITIATE FLASH FLOODING IN THESE AREAS THROUGH THE EARLY AFTERNOON
HOURS.

HAYES

ATTN...WFO...FFC...GSP...MRX...OHX...

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

LAT...LON   36228455 36018418 35758407 34718375 33998391
            34438481 34768502 35228524 35528536 35728539
            36198508