MESOSCALE PRECIPITATION DISCUSSION 0373
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
130 PM EDT THU JUN 28 2018

AREAS AFFECTED...NORTHERN AL...NORTHWEST GA

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

VALID 281730Z - 282130Z

SUMMARY...CONVECTION TRAINING ALONG A LINE IN A HIGH MOISTURE
ENVIRONMENT COULD RESULT IN A FLASH FLOOD THREAT THIS AFTERNOON.

DISCUSSION...REGIONAL RADARS OVER TN/GA/AL SHOWED A BOWING LINE OF
CONVECTION CROSSING PORTIONS OF SOUTH CENTRAL TN ABOUT TO ENTER
NORTHERN AL. THE CONVECTION REMAINS STRONG...AS THE GOES-16 CLEAN
IR LOOP SHOWED CLOUD TOP TEMPERATURES NEAR MINUS 75 DEGREE
CELSIUS. THE CONVECTION WAS IN AN  AXIS OF 1.75/2.00 PRECIPITABLE
WATER AIR ALONG THE TN/AL BORDER. IN THIS AREA...THE KOHX RADAR
SHOWED HOURLY RAINFALL RATES BETWEEN 1.50/2.00 INCHES.

WHILE THE CONVECTION IS BOWING TO THE SOUTH...IT HAS RECENTLY
SHOWN SIGNS OF TRAINING NEAR THE TN/AL BORDER. THE SHORT TERM
TRAINING ALONG THE BOW SUPPORTS THE THREAT FOR FLASH FLOODING OVER
THIS REGION...DESPITE RELATIVELY HIGH FLASH FLOOD GUIDANCE VALUES
(GENERALLY BETWEEN 2.00 AND 3.00 INCHES). THE MOST RECENT
HRRR/EXPERIMENTAL HRRR SHOWED LOCAL RAINFALL AMOUNTS NEAR 3.00
INCHES OVER PORTIONS OF NORTHERN AL...AND BASED ON RADAR
TRENDS...THESE AMOUNTS SEEM PLAUSIBLE.

WIND AND HAIL MAY REMAIN THE PRIMARY THREATS WITH THE CONVECTION
AS IT DROPS SOUTH INTO NORTHERN AL...BASED ON THE DISTRIBUTION OF
THE INSTABILITY IN THE COLUMN. HOWEVER...THE DEEP MOISTURE IN
PLACE...AND THE POTENTIAL FOR SHORT TERM TRAINING...SUGGEST THAT
FLASH FLOODING IS POSSIBLE THIS AFTERNOON.

HAYES

ATTN...WFO...BMX...FFC...HUN...MEG...MRX...OHX...

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

LAT...LON   35398757 35098564 34638484 33718535 33688677
            34038782 35088822