MESOSCALE PRECIPITATION DISCUSSION 0367
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
100 PM EDT WED JUN 27 2018

AREAS AFFECTED...EASTERN TN

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

VALID 271700Z - 272100Z

SUMMARY...CONVECTION TRAINING IN A HIGH MOISTURE ENVIRONMENT COULD
PRODUCE HOURLY RAINFALL RATES APPROACHING 2.00 INCHES... WHICH IN
TURN MAY POSE A FLASH FLOOD THREAT THIS AFTERNOON.

DISCUSSION...REGIONAL RADARS CONTINUE TO SHOW CONVECTION MOVING
EASTWARD AHEAD OF A SHORT WAVE CROSSING CENTRAL TN EARLY THIS
AFTERNOON. THE CONVECTION IS TAPPING 500-1000 J/KG OF MUCAPE
EXTENDING OVER NORTHEAST TN INTO FAR WESTERN VA/FAR WESTERN
NC...AND THE LIFT ASSOCIATED WITH THE SHORT WAVE HAS ALLOWED THE
CONVECTION TO MAINTAIN SOME ORGANIZATION AS IT TRACKS EASTWARD.

THE CONVECTION IS FOLLOWING AN AXIS OF 1.75/2.00 INCH PRECIPITABLE
WATER AIR THAT EXTENDS ACROSS TN...AND THE DEEP MOISTURE HAS
RESULTED IN HOURLY RAINFALL RATES BETWEEN 1.50 AND 2.00 INCHES
OVER NORTH CENTRAL TN (BASED ON THE KOHX RADAR). AS THE COLUMN HAS
MOISTENED...HAIL CONTAMINATION APPEARS TO BE LESS OF AN
ISSUE...AND RECENT SURFACE OBSERVATIONS HAVE SHOWN HOURLY RAINFALL
RATES CLOSE TO 1.50 INCHES WITHIN THE PAST HOUR.

CLOUD OVER OVER EASTERN TN MAY PREVENT INSTABILITY AHEAD OF THE
SHORT WAVE FROM INCREASING MUCH ABOVE THE CURRENT LEVELS... SO THE
EXTENT OF CONVECTION MAY NOT CHANGE MUCH GOING THROUGH THE
AFTERNOON. THE MOST RECENT HRRR/EXPERIMENTAL HRRR SHOW LOCAL 2.00
TO 4.00 INCH RAINFALL AMOUNTS OVER PORTIONS OF NORTHEAST TN (WITH
THE EXPERIMENTAL HRRR SHOWING THE HIGHEST AMOUNTS. THE NATIONAL
WATER MODEL INDICATED SOIL CONDITIONS NEARING SATURATION ACROSS
PORTIONS OF EASTERN TN...AND COLLABORATION WITH WFO MRX CONFIRMED
WET SOIL CONDITIONS.

SINCE INSTABILITY MAY END UP BEING A LIMITING FACTOR FOR A MORE
WIDESPREAD FLASH FLOOD THREAT...FLASH FLOODING IS ONLY CONSIDERED
POSSIBLE AT THIS POINT.

HAYES

ATTN...WFO...GSP...JKL...MRX...OHX...

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

LAT...LON   36688273 35928268 35488369 35578543 36618489