MESOSCALE PRECIPITATION DISCUSSION 0181
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
833 AM EDT WED MAY 03 2017

AREAS AFFECTED...SOUTHEASTERN TX/SOUTHWESTERN LA...

CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE

VALID 031232Z - 031702Z

SUMMARY...A WAVY BOUNDARY FEATURING A SHARP DEW POINT GRADIENT
WILL REMAIN A FOCUS FOR ACTIVE CONVECTION THIS MORNING. MULTIPLE
CELLS HAVE ALREADY ERUPTED ACROSS SOUTHEAST TX AND INTO THE
ADJACENT GULF COAST WATERS. RECENT CAMS SUGGEST AN INCREASINGLY
MORE ORGANIZED EVENT UNFOLDING DURING THE NEXT FEW HOURS WHICH
SUPPORTS AN INHERENT FLASH FLOOD RISK.

DISCUSSION...GPS SOUNDER DATA INDICATED A FAIRLY SHARP
PRECIPITABLE WATER GRADIENT BOUNDING TX/LA. 10Z DATA SHOWED PWAT
VALUES IN THE 1.50 TO 1.75 INCH RANGE EXTENDING FROM SOUTHEAST TX
DOWN THE COASTLINE WHILE VALUES ROUGHLY AN INCH LESS WERE MORE
COMMONPLACE OVER A VAST MAJORITY OF LA. WITHIN AN UNCAPPED
ENVIRONMENT...PER THE 11Z RAP OBJECTIVE ANALYSIS...EARLY MORNING
THUNDERSTORMS HAVE DEVELOPED ALONG THE UPPER TX GULF COAST AND
MOVED INLAND AT A FAIRLY HEFTY CLIP. THERE ARE PLENTY OF VARIABLES
SUPPORTING AN EXPANSION OF THE PRECIPITATION SHIELD. THIS INCLUDES
AMPLE MOISTURE (PWATS OF 1.75 INCHES AND SURFACE DEW POINTS NEAR
75 DEGREES)...SUFFICIENT UPPER DIFFLUENCE...ABUNDANT
INSTABILITY...AND A WAVY EAST/WEST LOW-LEVEL BOUNDARY IN PLACE.

BASED ON THE FORECAST OF SURFACE-BASED INSTABILITY PARAMETERS THE
NEXT SEVERAL HOURS...THE REGION REMAINS FOR THE MOST UNCAPPED
WHICH SHOULD SUPPORT ADDITIONAL CONVECTIVE DEVELOPMENT THROUGH THE
MORNING AND INTO THE EARLY AFTERNOON. THE IDEA IS FOR MUCH OF THIS
ACTIVITY TO LATCH ONTO THE AFOREMENTIONED EAST/WEST BOUNDARY WHICH
MAY LEAD TO AN EXTENSIVE PERIOD OF TRAINING/BACKBUILDING. THE
HIGH-RESOLUTION MODEL SUITE FAVORS SUCH AN
EVOLUTION...PARTICULARLY THE 00Z HRW-ARW/NSSL-WRF AND RECENT RUNS
OF THE HRRR. FOR THE MOST PART...THE REGION HAS BEEN ON THE DRIER
SIDE THE PAST COUPLE OF WEEKS WHICH SHOULD INITIALLY MITIGATE ANY
EXTENSIVE FLASH FLOOD RISK. AN EXCEPTION IS ON THE FAR EASTERN
SIDE OF THE MPD WHERE A FEW PARISHES ACROSS SOUTHWESTERN LA
(JEFFERSON DAVIS...ALLEN...AND EVANGELINE) HAVE SEEN HEAVY
PRECIPITATION SINCE LATE APRIL.

RUBIN-OSTER

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

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

LAT...LON   30839320 30529211 30029185 29299220 29529302
            29509395 29269472 29709543 30399515 30799424