MESOSCALE PRECIPITATION DISCUSSION 0118
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1127 PM EDT SAT MAY 23 2015
 
AREAS AFFECTED...SOUTHERN TX 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 240327Z - 240927Z
 
SUMMARY...THUNDERSTORMS WITH HOURLY RAIN RATES OCCASIONALLY
EXCEEDING 2" AN HOUR SHOULD CAUSE FLASH FLOODING.

DISCUSSION...AN ORGANIZED THUNDERSTORM COMPLEX, IN THE FORM OF A
LEWP/QLCS, HAS BEEN MOVING THROUGH SOUTH-CENTRAL TX AND NORTHEAST
MX WITH A HISTORY OF 2-3" AN HOUR RAINFALL PER AREA RADAR
ESTIMATES.  A REPORT FROM BLANCO, TX INDICATED THAT 9.31" FELL
WITH THE COMPLEX AS IT MOVED BY.  IT HAS STRENGTHENED A COLD POOL
AND OUTFLOW BOUNDARY, WHICH EXTENDS FROM THE ARKLATEX SOUTHEAST
ACROSS SAN ANTONIO INTO NORTHEAST MX.  INFLOW INTO THE BOUNDARY OF
40+ KTS AT 850 HPA HAS BEEN INDICATED BY AREA VAD WIND PROFILES.
MUCAPE VALUES OF 2000-4000 J/KG LIE AHEAD OF THE BAND. 
PRECIPITABLE WATER VALUES OF 1.75-2" EXIST ACROSS THE REGION,
WHICH GENERALLY SUPPORT THE RAINFALL RATES ADVERTISED BY RADAR.

CONVECTIVE PROPAGATION ACROSS THE REGION IS 25 KTS TO THE EAST. 
TEMPERATURES AT 700 HPA ARE COOLING, ELIMINATING REMNANT CAPPING
ALOFT.  DESPITE ITS FORWARD MOTION, RADAR ESTIMATES SHOW HOURLY
RAIN RATES OF 1.5-2", WHICH SHOULD EXCEED FLASH FLOOD GUIDANCE
VALUES OVER PORTIONS OF THIS REGION.  THE MESOSCALE QPF GUIDANCE
SHOWS A STRONG SIGNAL FOR 3-6" LOCALLY IN THIS AREA, WITH THE 12Z
RUNS OF THE ARW, SPCWRF, WRF4NSSL, AND 02Z HRRR RUNS APPEARING TO
CAPTURE ITS FORWARD PROPAGATION THE BEST.  WITH HOURLY RAIN RATES
UP TO 2.25" POSSIBLE, FLASH FLOODING IS CONSIDERED LIKELY.

ROTH

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

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

LAT...LON   32639609 32109503 30779456 29279486 27499712 
            27079728 25949704 25839771 26149879 26179968 
            26559985 28019974 28779946 29569850 31039798 
            32359711