MESOSCALE PRECIPITATION DISCUSSION 0588
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
328 AM EDT SUN AUG 21 2016
 
AREAS AFFECTED...PORTIONS OF SOUTHERN AND SOUTHEAST TX 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 210727Z - 211300Z
 
SUMMARY...EXTREMELY HEAVY RAINFALL WILL LIKELY PERSIST THROUGH THE
OVERNIGHT HOURS AND INTO THE EARLY MORNING WITH SIGNIFICANT AND
POSSIBLY LIFE-THREATENING FLASH FLOODING EXPECTED TO CONTINUE.

DISCUSSION...AREA RADARS SHOW TWO WELL DEFINED MCVS MAKING THEIR
WAY ACROSS PARTS OF TX AS OF 07Z WITH THE ONE OVER EASTERN TX
REMAINING FAIRLY PROGRESSIVE.  THERE WAS AN AXIS OF STORMS
PRODUCING INTENSE RAINFALL TO THE SOUTH AND SOUTHWEST OF THE
OLDEST MCV ALONG A WELL-DEFINED CONVECTIVELY REINFORCED BOUNDARY
THAT HAS BEEN  INTERCEPTING VERY MOIST AND UNSTABLE AIR POOLING
NORTH OUT OF SOUTH TX...WITH PWATS OF 2.2 TO 2.4 INCHES AND MLCAPE
VALUES OF 2500 J/KG. 

A SECOND MCV DEVELOPED OVER SOUTH TX AND IT APPEARS TO HAVE AIDED
ONSHORE FLOW AHEAD OF ITSELF AND HELPED ENHANCE A SECOND AREA OF
HEAVY RAINFALL TO ITS NORTH AND NORTHWEST.

THE SET-UP FOR THE REMAINDER OF THE OVERNIGHT FAVORS THE
CONTINUATION OF A SW/NE ORIENTED AREA OF EXTREMELY HEAVY
CONVECTIVE RAINFALL AS A SURFACE BOUNDARY TO THE NORTH AND WEST
BEGINS TO STALL OUT.  THE UPPER LEVEL FLOW IS RELATIVELY DIVERGENT
WITH PERSISTENTLY MOIST/UNSTABLE BOUNDARY LAYER TO FOCUS AND
SUSTAIN HEAVY RAINFALL. 

THE HRRR AND THE PARALLEL VERSION OF THE HRRR CONTINUE TO INDICATE
HEAVY RAINFALL AMOUNTS WHILE THE 00Z GLOBAL GUIDANCE HAS BEEN TOO
FAR TO THE NORTH.  THE LATEST CONVECTIVE ALLOWING MODELS STILL
DEPICT SOME LOCATIONS RECEIVING ANOTHER 2 TO 5 INCHES FROM SAN
MARCOS TOWARDS COTULLA AND THEN TO REGION SOUTH OF LAREDO.  

THIS AMOUNT OF RAINFALL WILL WORSEN ANY ONGOING FLOODING...WITH
THE POTENTIAL FOR SIGNIFICANT AND LIFE THREATENING FLOODING TO
CONTINUE INTO EARLY SUNDAY MORNING. 

BANN

ATTN...WFO...BRO...CRP...EWX...FWD...HGX...SHV...

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

LAT...LON   31659462 31469442 31079467 30299509 29259616 
            28079738 26639811 26299852 26479908 26859926 
            27249947 27569949 27729971 27949990 28200004 
            29359894 30439747 31099593