MESOSCALE PRECIPITATION DISCUSSION 0130
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
301 PM EDT MON APR 18 2016
 
AREAS AFFECTED...UPPER TX COAST...SOUTHWEST LA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 181857Z - 190000Z
 
SUMMARY...VERY INTENSE RAINS ARE EXPECTED TO CONTINUE NEAR THE
GULF COAST ALONG THE TX/LA BORDER OVER THE NEXT FEW HOURS.

DISCUSSION...GOES-14 SRSO IR IMAGERY SHOWS A CLUSTER OF
COLD-TOPPED CONVECTION JUST OFF THE GULF COAST AND EXTENDING NORTH
ALONG A VERY SLOW-MOVING OUTFLOW BOUNDARY UP ACROSS THE FAR UPPER
TX COAST AND INTO EXTREME SOUTHWEST LA. CLOUD TOPS HAVE COOLED A
LITTLE OVER THE LAST COUPLE OF HOURS HERE AND RADAR IMAGERY
SUGGESTS A SMALL SCALE MCV AND WEAK MESO-LOW ALONG THE TX/LA
BORDER WHICH IS HELPING TO FOCUS THE CONVECTION ACROSS THIS AREA.
THE EXPERIMENTAL GLD-LIGHTNING DENSITY PRODUCT HAS SHOWN A SLIGHT
UPTICK IN STRIKE ACTIVITY THE LAST HOUR TOO WHICH SUGGESTS
STRONGER VERTICAL ASCENT.

THE BLENDED-TPW PRODUCT SHOWS A NOSE OF 1.5 TO 1.75 INCH PWATS
NOSING UP THROUGH THE NORTHWEST GULF OF MEXICO AND INTO SOUTHWEST
LA...WHICH IS CONFIRMED BY GPS-DERIVED VALUES NEAR KLCH.
MEANWHILE...JUST AHEAD OF THE MCV THERE IS A NOSE OF MODEST
INSTABILITY WITH MUCAPE VALUES OF 1000 TO 2000 J/KG JUST OFFSHORE.
THE COMBINATION OF THE TWO PARAMETERS WILL LIKELY MAINTAIN THE
ONGOING CONVECTION OVER THE NEXT FEW HOURS WITH LOCALLY VERY
INTENSE RAINFALL RATES THAT MAY REACH CLOSE TO 3 INCHES/HR.

THE 12Z NMMB HAS A RELATIVELY DECENT HANDLE ON AT LEAST THIS
CONVECTIVE THREAT THROUGH THE LATE AFTERNOON HOURS...AND IT
SUGGESTS ADDITIONAL RAINFALL AMOUNTS OF 4 TO 6 INCHES THROUGH 00Z
WITH ISOLATED HEAVIER AMOUNTS. THIS WILL MAINLY BE A FUNCTION OF
NOT ONLY THE INTENSE RATES...BUT VERY SLOW FORWARD PROPAGATION. AS
A RESULT...ADDITIONAL FLASH FLOODING WILL BE POSSIBLE.

ORRISON

ATTN...WFO...LCH...SHV...

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

LAT...LON   31479314 30849272 29749270 29409321 29569391 
            30539408 31469394