MESOSCALE PRECIPITATION DISCUSSION 0347
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
201 AM EDT TUE JUN 14 2016
 
AREAS AFFECTED...SOUTHERN AR...NORTHERN LA/FAR NORTHEAST TX 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 140600Z - 141200Z
 
SUMMARY...CONVECTION DEVELOPING ALONG AN AXIS OF LOW LEVEL
CONFLUENCE IN A VERY MOIST COLUMN COULD PRODUCE VERY HEAVY
RAINFALL AMOUNTS...WITH FLASH FLOODING EXPECTED THROUGH THE EARLY
MORNING HOURS. 

DISCUSSION...CONVECTION IS BEGINNING TO DEVELOP ACROSS SOUTHERN
AR/NORTHERN LA... ALONG A LINE OF LOW LEVEL CONVERGENCE. THE
BLENDED TPW PRODUCT AND THE LATEST RAP BASED PRECIPITABLE WATER
ANALYSIS SHOWED VALUES BETWEEN 2.20 AND 2.30 INCHES... WHICH IS
BETWEEN TWO AND THREE STANDARD DEVIATIONS ABOVE THE MEAN.
INSTABILITY HAS BEEN A LIMITING FACTOR FOR CONVECTION THUS
FAR...WITH MLCAPE VALUES GENERALLY LESS THAN 500 J/KG.

HOWEVER...HIGHER MLCAPE VALUES (GENERALLY BETWEEN 1000 AND 1500
J/KG) ARE AVAILABLE OVER PORTIONS OF NORTHEAST AND CENTRAL
TX...AND THE LOW AND MID LEVEL FLOW IS EXPECTED TO TRANSPORT THE
HIGHER INSTABILITY AIR INTO THE REGION. IN ADDITION...A CLOSED MID
LEVEL CIRCULATION OVER EASTERN OK/WESTERN AR WILL INCREASE THE
DIFFLUENT FLOW OVER THE LOWER MS VALLEY...AIDING IN ADDITIONAL
CONVECTIVE DEVELOPMENT. 

THERE IS SOME MODEL SPREAD CONCERNING THE PLACEMENT OF THE MOST
SIGNIFICANT CONVECTION (SOUTHERN AR AS OPPOSED TO NORTHERN
LA)...WITH THE DEVELOPMENT SO FAR FAVORING SOUTHERN AR. A PORTION
OF FAR NORTHEAST TX WAS INCLUDED IN THE AREA...AS NESDIS SAB
POINTED OUT THIS AREA WILL BE ON THE EDGE OF THE INSTABILITY
GRADIENT AS WELL. 

DEVELOPMENT IS EXPECTED TO CONTINUE ALONG THE LOW LEVEL CONFLUENCE
AXIS THROUGH 09Z...WHEN THE LATEST HRRR/RAP/00Z ARW SHOW THE
MAXIMUM INTENSITY TO OCCUR. DEVELOPMENT ALONG THE AXIS WILL
FACILITATE BACKBUILDING...WHICH COULD LEAD TO SOME IMPRESSIVE
RAINFALL TOTALS THROUGH 12Z. 

THE LATEST HRRR/EXPERIMENTAL HRRR AND 00Z WRF ARW SUGGEST LOCAL 4
TO 6 INCH RAINFALL AMOUNTS ALONG THE AXIS...THOUGH THERE ARE SOME
POSITIONAL DIFFERENCES NOTED. IN ANY EVENT...RAINFALL TOTALS THIS
HIGH ARE EXPECTED TO RESULT IN FLASH FLOODING ACROSS SOUTHERN
AR/NORTHERN LA/FAR NORTHEAST TX THROUGH THE EARLY MORNING HOURS.

HAYES

ATTN...WFO...JAN...LZK...SHV...

ATTN...RFC...ABRFC...LMRFC...WGRFC...

LAT...LON   34029217 33849128 33229099 32669094 32219176 
            31989295 32079410 32719513 33419480 33949373