MESOSCALE PRECIPITATION DISCUSSION 0302
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
233 PM EDT SAT JUL 04 2015
 
AREAS AFFECTED...CENTRAL/SOUTHERN LA...CENTRAL/SOUTHERN
MS...WESTERN AL... 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 041835Z - 042335Z
 
SUMMARY...CONVECTION EXTENDING ALONG AN OUTFLOW BOUNDARY FROM
NORTHERN AND CENTRAL LA ACROSS CENTRAL MS AND WESTERN AL COULD
MERGE WITH CONVECTION DEVELOPING SOUTH OF THE OUTFLOW. CELL
MERGERS AND SUBSEQUENT TRAINING COULD RESULT IN FLASH FLOODING.

DISCUSSION...CONVECTION FORMING/SPREADING OUT ALONG AN OUTFLOW
BOUNDARY STRETCHING ACROSS NORTHERN AND CENTRAL LA INTO CENTRAL
MS/AL CONTINUES TO PUSH SOUTHEAST WITH THE BOUNDARY. THIS ACTIVITY
HAS WEAKENED A BIT DURING THE PAST 2 HOURS...BUT STILL HAS THE
POTENTIAL TO PRODUCE HIGH RAINFALL RATES.

MEANWHILE...SCATTERED CONVECTION CONTINUES TO DEVELOP IN THE
BETTER INSTABILITY POOL ACROSS SOUTHERN LA AND SOUTHERN MS. THE
ACTIVITY REMAINS SCATTERED AT THIS TIME...AS THE BETTER SYNOPTIC
SCALE ASCENT REMAINS NORTH OF THE AREA. RAINFALL RATES WITH THIS
BATCH OF CONVECTION HAS AVERAGED BETWEEN ONE AND TWO INCHES AN
HOUR...BASED ON KPOE RADAR ESTIMATES.

ONE AND THREE HOUR FLASH FLOOD GUIDANCE VALUES ARE RELATIVELY HIGH
ACROSS THIS AREA (GENERALLY BETWEEN TWO AND THREE INCHES)... AS
MUCH OF THE HEAVY RAIN DURING THE PAST FEW DAYS HAS BEEN NORTH OF
THE REGION. HOWEVER...THE COMBINATION OF INSTABILITY (WITH SBCAPE
VALUES BETWEEN 2000-3000 J/KG) AND HIGH MOISTURE CONTENT AIR
(PRECIPITABLE WATER VALUES NEAR 2.00 INCHES) SHOULD PRODUCE
CONVECTION ACROSS SOUTHERN LA AND SOUTHERN MS WITH HIGH RAINFALL
RATES.

THERE IS THE POTENTIAL FOR LOCAL 2-3 INCH RAINFALL
AMOUNTS...PARTICULARLY WHERE CELLS MERGE AND/OR TRAINING OCCURS.
THESE AMOUNTS ARE SUPPORTED BY THE LATEST HRRR RUN. THIS MUCH RAIN
COULD BE ENOUGH TO PRODUCE FLASH FLOODING. THE THREAT SHOULD
CONTINUE INTO THE LATE AFTERNOON HOURS...BEFORE THE CONVECTION
WITH THE OUTFLOW BOUNDARY STARTS TO WEAKEN...AND THE SOUTHERN
LA/SOUTHERN MO CONVECTION LOSES THE BENEFIT OF DAYTIME HEATING.

HAYES

ATTN...WFO...BMX...JAN...LCH...LIX...MOB...SHV...

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

LAT...LON   33348690 33128633 32708618 32478624 32348635 
            31708701 31038807 30868872 30528927 29799102 
            30099287 30439350 30439353 31149368 31839245 
            31859050 32508929 33028850 33088835 33258774 
            33328758