Flash Flood Guidance
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000
AWUS01 KWNH 301615
FFGMPD
LAZ000-MSZ000-TXZ000-302044-

MESOSCALE PRECIPITATION DISCUSSION 0335
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1214 PM EDT SAT AUG 30 2014

AREAS AFFECTED...FAR EAST TX/LA/WEST CENTRAL MS...

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

VALID 301614Z - 302044Z

SUMMARY...HEAVY RAINFALL CONTINUES TO FALL ACROSS MUCH OF THE
STATE OF LA. MESONET OBSERVATIONS SHOW 4 TO 7 INCHES HAS ALREADY
FALLEN ACROSS SOUTHWESTERN LA DURING THE PAST 6 HOURS WITH A LOCAL
MAXIMA IN LAKE CHARLES. EXPECT THE FOCUS OF DEEP CONVECTION TO
GRADUALLY SLIDE EASTWARD THROUGH THE AFTERNOON. FLASH FLOODING
WILL BE KEPT AT POSSIBLE GIVEN RATHER HIGH FFG VALUES.

DISCUSSION...AN INCREDIBLY MOIST AIR MASS IS IN PLACE ACROSS THE
WESTERN TO CENTRAL GULF COAST. THE 12Z RAOB AT LCH SHOWED A PWAT
OF 2.65 INCHES WHICH IS ABOVE THE 99TH PERCENTILE AND RANKS 2ND
HIGHEST ON RECORD FOR AUGUST AT THIS SITE. PERSISTENT LOW-LEVEL
ADVECTION OF ENHANCED MOISTURE AND MODEST INSTABILITY CONTINUES TO
ALLOW REDEVELOPMENT OF CONVECTION ACROSS THE OFFSHORE WATERS OF
LA. THE 15Z RAP FORECAST SHOWS MIXED LAYER CAPES OF 1000 TO 1500
J/KG ADVECTING INLAND WITH CURRENT 850 TO 700 MB WINDS AROUND 30
KNOTS PER VAD WIND PROFILERS. THE THERMODYNAMIC ENVIRONMENT
REMAINS FAVORABLE FOR HEAVY RAINFALL TO CONTINUE WITH MOIST
ADIABATIC PROFILES TO NEARLY 400 MB AND WET BULB ZERO HEIGHTS UP
TO AROUND 16 KFT. THE WATER VAPOR IMAGERY AND BLENDED TPW PRODUCT
DO NOT SHOW ANY HINT OF DRY AIR ENTRAINMENT OCCURRING SO VERY
EFFICIENT HEAVY RAINFALL PROCESSES ARE IN PLACE. THE MOST RECENT
VISIBLE SATELLITE IMAGERY AND LIGHTNING DATA SHOW THE ACTIVITY
ACROSS SOUTH-CENTRAL LA HAS BECOME MORE CONVECTIVE IN NATURE GIVEN
THE RAPID INCREASE IN CLOUD-TO-GROUND LIGHTNING.

THE HIGH-RESOLUTION MODELS UNANIMOUSLY AGREE ON SHIFTING THE FOCUS
EASTWARD WHICH CONCURS WITH THE CURRENT RADAR/SATELLITE TRENDS.
EXPECT RAINFALL RATES OF 2 TO 3 INCHES PER HOUR TO PERSIST GIVEN
THE PREVIOUS HISTORY OF THE EARLY MORNING ACTIVITY.
ADDITIONALLY...THERE HAVE ALREADY BEEN REPORTS OF FLASH FLOODING
IN SPITE OF THE HIGHER END FFG.


RUBIN-OSTER

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

ATTN...WFO...JAN...LIX...LCH...SHV...

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

LAT...LON   31209336 32429246 32889218 32909149 32379110 31569104
            31039041 30498980 29278957 28768993 28719079 28909158
            29089248 29169349 29629387 30589369 31209336


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