MESOSCALE PRECIPITATION DISCUSSION 0589
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
856 AM EDT SUN AUG 21 2016
 
AREAS AFFECTED...SOUTH TEXAS AND ADJECENT NE MEXICO 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 211300Z - 211800Z
 
SUMMARY...CONVERGENCE BAND WITH HIGHLY EFFICIENT RAINFALL
PRODUCTION MAY POSE ISOLATED FLASH FLOOD CONCERNS DUE TO HIGH
RATES AND WET ANTECEDENT CONDITIONS.

DISCUSSION...RADAR AND SATELLITE MOSAIC LOOPS INDICATE A STRONG
MCV OVER S GONZALES COUNTY WITH A BROAD CONFLUENCE ZONE/TROF
EXTENDING NORTHEASTWARD ACROSS EASTERN TEXAS TOWARD FRONTAL ZONE
NEAR/ALONG LA/AR BORDER.  UPPER LEVEL JET STREAK SPEED MAX
ENHANCED BY LAST NIGHT'S MCS ACTIVITY IS EXITING TOWARD THE
NORTHEAST AND SUPPORTING BROAD ASCENT ACROSS SE TX ATTM.  THIS
COMBINED WITH NORTHERLY CHANNEL OF EARLY MORNING ENHANCED ONSHORE
FLOW SUPPORTS STRONG MST CONVERGENCE ALONG A N-S BAND FROM
ROBERTSON COUNTY TO CALHOUN COUNTY ALONG THE EASTERN PERIPHERY OF
THE MCV.   DEEPLY SATURATED PROFILE (PARTICULARLY WESTWARD) WITH
TPWS ABOVE 2.0" WITH DOWNSTREAM AVAILABLE INSTABILITY DENOTED BY
CAPES UP TO 2000 J/KG (CLOSER TO THE COAST) SHOULD PRESENT THE
OPPORTUNITY FOR VIGOROUS CONVECTIVE UPDRAFTS WITH EFFICIENT WARM
CLOUD RAINFALL PRODUCTION FOR RATES IN THE 2-2.5"/HR RANGE.  SHORT
TERM CELL MOTIONS HAVE A SLIGHT NORTHERLY COMPONENT THAT MAY
SUPPORT SOME ISOLATED REPEAT ALLOWING FOR COMPOUNDED TOTALS...BUT
MOST HI-RES GUIDANCE SUPPORTED MOST STRONGLY BY THE 00Z WRF-ARW
SUGGEST EASTWARD ADVANCEMENT ACROSS SE TX THOUGH 19-20Z...LEADING
TO STREAKS OF 2-3" TOTALS.  VERY HIGH FFG VALUES WOULD SUGGEST
THIS IS NOT A THREAT...THOUGH AHPS INDICATES MUCH OF THE AREA WELL
ABOVE NORMAL (400% AND GREATER) OVER THE WEEK AND SHOWING A WET
MONTH AS WELL SUPPORTING THE NOTION OF ISOLATED FLASH FLOODING
CONDITIONS LIMITED TO STRONGEST CORES.  

GALLINA

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

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

LAT...LON   31309586 31099487 30619437 29769427 29409461 
            28839533 28279634 28389675 29079667 30319655 
            30999639