MESOSCALE PRECIPITATION DISCUSSION 0719
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
932 PM EDT WED AUG 23 2017

AREAS AFFECTED...CENTRAL TX...NORTHERN LA INTO SOUTHERN MS

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

VALID 240130Z - 240630Z

SUMMARY...SLOW MOVING CONVECTION ALONG A FRONTAL BOUNDARY IN A
HIGH MOISTURE ENVIRONMENT COULD RESULT IN A FLASH FLOOD THREAT
INTO THE EARLY MORNING HOURS.

DISCUSSION...EXPERIMENTAL GOES 16 CLEAN IR LOOP SHOWED SLOWLY
COOLING TOPS WITH CONVECTION DEVELOPING ALONG A FRONTAL BOUNDARY
EXTENDING FROM CENTRAL TX INTO SOUTHWEST MS THIS EVENING. THE
CONVECTION IS FORMING IN AN AXIS OF 1000-2000 J/KG OF MLCAPE ALONG
AND SOUTH OF THE FRONT (WITH BOTH THE 00Z FWD AND 00Z JAN
SOUNDINGS SHOWING SBCAPE VALUES BETWEEN 2500 AND 3500 J/KG).

DEEP MOISTURE (WITH PRECIPITABLE WATER VALUES NEAR 2.00
INCHES...BASED ON 00Z SOUNDINGS) STRETCHED ALONG THE FRONT IS
FOSTERING HIGH RAINFALL RATES WITH THE CONVECTION...WITH HOURLY
RAINFALL RATES GENERALLY BETWEEN 1.75 AND 2.25 INCHES. CELL
MOTIONS HAVE BEEN SLOWLY SOUTHWARD... AND THESE MOTIONS ARE
EXPECTED TO CONTINUE FOR THE NEXT FEW HOURS. 

THE COMBINATION OF SLOW CELL MOTIONS AND HIGH MOISTURE CONTENT AIR
WILL CONTINUE TO SUPPORT HIGH RAINFALL RATES STRETCHING FROM
CENTRAL TX ACROSS NORTHERN LA INTO SOUTHWEST MS. THE MOST RECENT
HRRR SHOWED LOCAL RAINFALL AMOUNTS IN EXCESS OF 5 INCHES OVER
PORTIONS OF NORTHEAST LA...WITH LESSER AMOUNTS SCATTERED ALONG THE
FRONT.

THUS FAR...THE CONVECTIVE COVERAGE HAS BEEN SCATTERED...AND THIS
COULD ULTIMATELY BE A LIMITING FACTOR FOR A MORE ORGANIZED FLASH
FLOOD THREAT. A BROAD WARM AIR ADVECTION PATTERN AHEAD OF A WEAK
SHORT WAVE TRACKING FROM NORTHEAST TX INTO NORTHERN MS COULD ALLOW
FOR A LARGER CONVECTIVE COVERAGE.

HOWEVER...SINCE THERE IS SOME SPREAD ON HOW MUCH CONVECTIVE
COVERAGE WILL OCCURS... FLASH FLOODING IS ONLY CONSIDERED POSSIBLE
AT THIS TIME.

HAYES

ATTN...WFO...EWX...FWD...HGX...JAN...LCH...LIX...SHV...

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

LAT...LON   32589099 32549020 32508998 32508997 31928923
            31278945 30959198 29939671 30059753 30879790
            32079701