MESOSCALE PRECIPITATION DISCUSSION 0207
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
232 AM EDT FRI AUG 09 2013
 
AREAS AFFECTED...WESTERN KY...NORTHWEST TN...NORTHEAST
AR...SOUTHEAST MO 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 090610Z - 091210Z
 
SUMMARY...THUNDERSTORMS WITH HEAVY RAINFALL WILL TRAIN FROM SW TO
NE. FLASH FLOODING IS POSSIBLE.

DISCUSSION...THIS REGION WAS IN THE WARM SECTOR OF A SFC FRONTAL
ZONE STRETCHING FROM AR/MO TO IN/OH. CONFLUENCE WAS ESTABLISHED
FROM 850-700 MB ALONG AND JUST NORTH OF AN AXIS OF UNSTABLE
AIR...WITH MUCAPES PREDICTED BY THE RAP AND SREF TO REMAIN NEAR
1000 J/KG...OR AT LEAST GREATER THAN 500 J/KG THROUGH MORNING.
SIMILAR VALUES WERE NOTED YESTERDAY WHEN TRAINING YIELDED A
SIGNIFICANT FLASH FLOOD EVENT AROUND NASHVILLE.

THE AXIS FOR HEAVY RAIN THIS MORNING HAS SET UP FARTHER
NORTH...BUT SOME PROPAGATION TO THE E AND S MAY EVENTUALLY BRING
HEAVY RAIN DOWN TO THE LATITUDE OF INTERSTATE 40 BY MORNING. IN
THE MEANTIME...THE GREATER THREAT FOR HEAVY RAINFALL WILL BE FROM
NE AR AND THE MO BOOT HEEL UP TO NEAR MORGANTOWN AND ELIZBETHTOWN
IN KY.

AGAIN DRAWING PARALLELS TO LAST NIGHT...INITIAL RADAR ECHOES
SHOWED SIMILAR HEAVY RAINFALL CHARACTER...WITH TOPS APPROACHING 50
KFT AND YET LITTLE HAIL INDICATED PER DUAL POL VARIABLES AND
ALGORITHMS. THE CONVECTIVE CLUSTER EAST OF PADUCAH SHOULD GROW AND
PERSIST...WHILE ACTIVITY FILLS IN ALONG THE NARROW CONFLUENCE AXIS
IN ADVANCE OF THE COLD POOL COMING OUT OF NORTHEAST AR. RECENT
RUNS OF THE HRRR INDICATE A GOOD DEAL OF TRAINING...AND SEVERAL
HIRES MODELS SHOW NARROW HEAVY RAIN SWATHS ALONG THIS AXIS. THEY
INCLUDE THE NAM CONEST AND SPC WRF. 

FLASH FLOOD GUIDANCE ALONG THE INITIAL AXIS IS GENERALLY 2 INCHES
IN 1 HOUR OR 3 INCHES IN 3 HOURS. GUIDANCE VALUES LOWER WITH
SOUTHWARD EXTENT INTO TN. WITH PW VALUES IN EXCESS OF 2
INCHES...WE COULD EASILY SEE RAIN RATES TO 3 INCHES PER
HOUR...WITH LOCAL ACCUMULATIONS EXCEEDING 4 INCHES ON ROUGHLY THE
2 OR 3 HOUR TIME SCALE WHEREVER TRAINING IS MOST EFFICIENT. 

BURKE

ATTN...WFO...JKL...LMK...OHX...PAH...MEG...

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

LAT...LON   36958446 36408592 35948756 35319007 35909076 36299047
            37038889 37938579 37948444 37468408 36958446