MESOSCALE PRECIPITATION DISCUSSION 0080
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
115 AM EDT TUE MAY 12 2015
 
AREAS AFFECTED...SOUTH TEXAS TOWARD UPPER TEXAS COAST 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 120513Z - 120930Z
 
SUMMARY...DEEP MOISTURE AND SLOW MOVING CELLS WILL CONTINUE TO
PROMOTE LOCALIZED RAINFALL RATES OF 2-3 IN/HR THROUGH 09Z. THE
FLASH FLOOD THREAT APPEARS GREATEST ACROSS DEEP SOUTH TEXAS AND
JUST INLAND OF THE THE CNTRL TEXAS COAST.

DISCUSSION...RECENT RADAR IMAGERY CONTINUES TO SHOW LOOSELY
ORGANIZED POCKETS OF VERY HEAVY RAINFALL ACROSS PORTIONS OF SOUTH
TEXAS. AT 05Z...A COUPLE OF EMBEDDED MESOSCALE VORTICES WERE
OBSERVED IN AN EWD MOVING...POORLY ORGANIZED LINE OF CONVECTION
MOVING THROUGH LA SALLE AND WEBB COUNTIES. IR SATELLITE IMAGERY
APPEARS TO SHOW THIS AS THE LAST OF CONVECTION MOVING OFF OF THE
SIERRA MADRE OF MEXICO WITH CLEARING TO THE WEST. FARTHER
SOUTH...A SLOW MOVING LINE OF HEAVY RAINFALL WITH DUAL POL
ESTIMATED RAINFALL RATES OF 2-3 IN/HR STRADDLED THE RIO GRANDE
INTO STARR AND HIDALGO COUNTIES. LASTLY...ALONG THE CNTRL TO UPPER
TEXAS COAST...THE HEAVIEST RAINFALL WAS EMBEDDED IN CONVECTION
JUST OFFSHORE OF MATAGORDA AND BRAZORIA COUNTIES NEAR AN REMNANT
OUTFLOW BOUNDARY. INDIVIDUAL CELL MOTIONS ARE SOMEWHAT
CHAOTIC...BUT GENERALLY MOVING NORTH TO EAST AT AROUND 10
KTS...WHILE 850-700 MB FLOW FROM THE SOUTHEAST IS PRESENT FROM
SOUTH TEXAS INTO THE WRN GULF OF MEXICO...FAVORING SEWD
PROPAGATION AND BRIEF PERIODS OF TRAINING RAINS.

GIVEN PRECIPITABLE WATER VALUES ARE ABOVE 2 INCHES PER 00Z CRP/BRO
RAOBS...AND PERHAPS AS HIGH AS RECENT GPS SITE PW OF 2.40 INCHES
AT CRP AT 03Z...DEEP TROPOSPHERIC MOISTURE IS PRESENT AND NOT
GOING ANYWHERE ANYTIME SOON. POTENTIAL BACK EDGE OF HEAVY RAIN
MOVING THROUGH WEBB AND LA SALLE COUNTIES SHOULD CONTINUE TO MOVE
EAST...WHILE POTENTIAL FOR AN ADDITIONAL 3-5 INCHES EXISTS ACROSS
DEEP SOUTH TEXAS AND IN THE VICINITY OF THE AFOREMENTIONED OUTFLOW
BOUNDARY ALONG THE CNTRL TEXAS COAST. 

ADDITIONAL FLASH FLOODING IS POSSIBLE...BUT DOES NOT APPEAR TO BE
A WIDESPREAD THREAT. THERE IS A SOLID CONSENSUS IN THE LATEST
HI-RES MODELS SHOWING THIS EVOLUTION WHICH ALLOWS FOR MODERATE
CONFIDENCE.  

OTTO

ATTN...WFO...BRO...CRP...EWX...HGX...

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

LAT...LON   29439549 28819521 28109614 27279680 25809718 
            25999878 26799954 27559958 28399944 28639849 
            28679734 29239608