Flash Flood Guidance
Issued by NWS

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000
AWUS01 KWNH 011439
FFGMPD
LAZ000-TXZ000-011900-

MESOSCALE PRECIPITATION DISCUSSION 0161
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1038 AM EDT SUN MAY 01 2016

AREAS AFFECTED...UPPER TX COAST...SOUTHERN LA

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

VALID 011430Z - 011900Z

SUMMARY...BACKBUILDING AND TRAINING CONVECTION WILL BE A CONCERN
OVER THE NEXT FEW HOURS ALONG THE FAR UPPER TX COAST AND ACROSS
FAR SOUTHERN LA. GIVEN RECENT HEAVY RAINFALL...ADDITIONAL FLASH
FLOODING WILL BE POSSIBLE.

DISCUSSION...SEVERAL COLD-TOPPED AND VERY SLOW MOVING CONVECTIVE
CLUSTERS OVER SOUTHERN LA ARE LIKELY TO PERSIST THROUGH
MID-AFTERNOON WHILE GRADUALLY CONSOLIDATING AND SETTLING OFF TO
THE SOUTHEAST. IN FACT...SURFACE OBSERVATIONS SHOW A RATHER
WELL-DEFINED COLD POOL IN RESPONSE TO THE CONVECTIVE
ORGANIZATION...AND THIS IS ALLOWING FOR AN OUTFLOW BOUNDARY TO
GRADUALLY BOW OUT IN AN ANTICYCLONIC FASHION. THE SOUTHERN FLANK
OF THE OUTFLOW BOUNDARY IS FOCUSING STRONG CONVECTION WITH SLOW
MOVEMENT AND VERY HEAVY RAINFALL RATES...AND THIS IS WHERE THE
CONCERN WILL BE OVER THE NEXT FEW HOURS.

ENHANCED MOISTURE CONVERGENCE ALONG THIS BOUNDARY INVOLVING THE
UPPER TX COAST AND  SOUTHERN LA WILL BE INTERACTING WITH A
MODERATELY UNSTABLE AIRMASS ADVECTING NORTH IN OFF THE NORTHERN
GULF OF MEXICO. MLCAPE VALUES ARE ALREADY LOCALLY OVER 2000
J/KG...WITH PWATS OVER THIS AREA OF 1.7 TO 1.8 INCHES. THIS IS
EXPECTED TO RESULT IN AN ENVIRONMENT CONDUCIVE FOR BACKBUILDING
AND TRAINING CONVECTION AT LEAST OVER THE NEXT FEW HOURS.

EXPECT RAINFALL RATES OF 2 TO 2.5 INCHES/HR WITHIN THE STRONGER
CONVECTIVE CORES AND ESPECIALLY WITH ANY OVERSHOOTING TOPS. SOME
OVERSHOOTING TOPS HAVE BEEN VALIDATED BY THE GOES-OTD ALGORITHM
NOT FAR SOUTH OF BATON ROUGE OVER THE LAST 30 MINUTES.

ADDITIONAL STORM TOTAL RAINS OF 3 TO 5 INCHES WILL BE POSSIBLE
THROUGH 19Z. CONSIDERING THE RECENT HEAVY RAINFALL ACROSS THE
THREAT AREA...ADDITIONAL FLASH FLOODING AND/OR RUNOFF PROBLEMS
WILL BE POSSIBLE.

ORRISON

...PLEASE SEE WWW.WPC.NCEP.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...LCH...LIX...

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

LAT...LON   30609063 30589007 30378973 30168957 29718960
            29299003 29139076 29419163 29579248 29649343
            29609419 29959432 30219376 30419270 30409173
            30449126


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