MESOSCALE PRECIPITATION DISCUSSION 0327
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1050 AM EDT TUE JUN 19 2018

AREAS AFFECTED...SOUTHEAST TX...EXT SOUTHWESTERN LA...

CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY

VALID 191450Z - 191950Z

SUMMARY...GREATER UNCERTAINTY IN PRECISE LOCATIONS BUT GIVEN
EXTREMELY DEEP MOISTURE AND POTENTIAL FOR TRAINING BANDS...FLASH
FLOODING IS CONSIDERED LIKELY NEAR/ALONG THE SOUTHEAST TX COASTAL
REGION.

DISCUSSION...OUTER N-S ORIENTED CONVERGENCE BAND CONTINUES TO
PRODUCE PROLIFIC RAINFALL RATES OVER 2"/HR TRAINING.  UPPER LEVEL
SHORTWAVE THAT HAD BEEN INFLUENCING THIS LOW LEVEL CONVERGENCE
BAND BY LEADING SW TO NE CLOUD BEARING FLOW HAS EXITED TOWARD THE
NORTHEAST AND MEAN CLOUD BEARING FLOW HAS BEEN BACKING RECENTLY
AND BANDS ARE STARTING TO REFOCUS JUST OFFSHORE.  WEST OF THE
BAND...CLEARING SKIES ARE SUPPORTING INCREASING INSOLATION TO ADD
INSTABILITY TO THE UNSTABLE BUT SKINNY PROFILES PER LCH 12Z
SOUNDING...LEADING TO CAPES OVER 2000 TO 3000 J/KG.  STRONG MST
CONVERGENCE AND FLUX SUPPORTS 3-4"/HR RAINFALL RATES ESPECIALLY IN
THE TRAINING CONVECTION...AND LEAD TO LIKELY FLASH FLOODING RISK.

A SECONDARY BAND IN THE WESTERN GULF IS UNDER GREATER INFLUENCE OF
THE MCV/NARROW SYNOPTIC INVERTED MID-LEVEL TROF OVER DEEP SOUTH
TX.  MEAN FLOW IS DIRECTING THIS BAND NORTHWARD BUT RECENT VIS/IR
IMAGERY SUGGESTS SOME STRONG INFLOW IN THE LOW LEVEL IS ALLOWING
FOR INCREASE EASTWARD PROPAGATION THAT WOULD DIRECT CELLS TOWARD
MATAGORDA BAY AND EASTWARD.  HI-RES GUIDANCE IS SPLIT IN DIRECTION
OF DEVELOPMENT AND LEAD TO MORE NUMEROUS NARROWLY FOCUSED OF SE-NW
BANDS WITH REDUCED UPDRAFT CORES AND LOWER RAINFALL RATES AND
AREAL COVERAGE...OR INTO LESS BUT BROADER BANDS.  THE LATTER GIVEN
THE POTENTIAL OF RATES/FLUX HAVE A HIGH  LIKLIHOOD OF PRODUCING
4-6" RAINFALL TOTALS OVER THE NEXT 4-6HRS WITH SOME LOCALIZED
SPOTS OF 8" POSSIBLE.  CURRENT RADAR TRENDS WOULD FAVOR THIS
LATTER SOLUTION GIVEN THE OUTFLOW BOUNDARIES ROLLING NORTHEAST
FROM BOTH BANDS HELPING TO CONSOLIDATE INTO ONE LARGER BAND
FURTHER NORTHEAST TOWARD GALVESTON BAY/NORTHEAST BRAZORIA COUNTY. 
THIS IS GENERALLY IN LINE WITH RECENT HRRR/RAP SOLUTIONS BUT A BIT
TOO FAR SOUTHWEST WITH NO ACCOUNTING FOR ONGOING BAND IN FAR SE
TX...SO THE AXIS OF HEAVIEST RAINFALL MAY BE FURTHER NORTHEAST
THAN THE HRRR/RAP SUGGEST. 

GALLINA

ATTN...WFO...HGX...LCH...

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

LAT...LON   30979454 30949410 30479373 30039354 29689355
            29509406 29239471 29169487 28599584 28599616
            29049650 29729630 30359569 30929513