MESOSCALE PRECIPITATION DISCUSSION 0614
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1209 PM EDT SUN OCT 25 2015
 
AREAS AFFECTED...SOUTHERN LA...SOUTHWESTERN MS 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 251608Z - 252108Z
 
SUMMARY...VERY EFFICIENT WARM RAIN PROCESSES FUELED BY ANOMALOUS
MOISTURE  AND STRONG LOW LEVEL INFLOW WILL CONTINUE TO PRODUCE A
HEAVY RAIN THREAT ACROSS MUCH OF SOUTHERN LA.
 
DISCUSSION...LATEST OBSERVATIONS/SATELLITE IMAGERY SHOW THAT THE
WELL-DEFINED SURFACE LOW THAT DEVELOPED LATE YESTERDAY INTO THE
OVERNIGHT HOURS OVER THE NORTHWESTERN GULF OF MEXICO HAS NOW MOVED
JUST TO THE EAST OF OIL PLATFORM KGVX OFF OF THE UPPER TX COAST. 
THE CENTER IS EXPECTED TO CONTINUE TO TRACK TO THE ENE OVER THE
NEXT SEVERAL HOURS.  40-50 KT SOUTHEASTERLY 850 MB FLOW AHEAD OF
THE LOW WILL CONTINUE TO SUPPORT THE ANOMALOUSLY DEEP MOISTURE
ALREADY IN PLACE ALONG THE CENTRAL GULF COAST.  AT 2.15 AND 2.21
INCHES RESPECTIVELY...SPC SOUNDING CLIMATOLOGY SUGGESTS RECORD PWS
AT LCH AND LIX THIS MORNING.  LATEST MESOANALYSIS CONTINUES  TO
SHOW PWS OF 2-2.25 INCHES ACROSS THE OUTLOOK AREA. PWS MAY
INCREASE FURTHER THROUGH THE AFTERNOON HOURS AS STRONG SOUTHERLY
FLOW CONTINUES TO TAP A PLUME OF DEEP MOISTURE EXTENDING BACK INTO
THE SOUTHWESTERN GULF OF MEX.  MEANWHILE...DIFFLUENT FLOW ALOFT
AHEAD OF A SOUTHERN STREAM TROUGH MOVING ACROSS TX WILL CONTINUE
TO ENCOURAGE LARGER SCALE LIFT.  AS NOTED PREVIOUSLY...THE
LIMITING FACTOR FOR HEAVY RAINFALL RATES WILL CONTINUE TO BE
MARGINAL TO NEGLIGIBLE INSTABILITY...WITH THE LATEST MESOANALYSIS
SHOWING MUCAPE VALUES OF 100-500 J/KG ACROSS THE AREA.  WHILE THE
LATEST GUIDANCE SHOWS LITTLE CHANGE IN INSTABILITY DURING THE
AFTERNOON HOURS...CONVECTION NOW DEVELOPING EAST OF THE
LOW...WHICH WAS NOTED BY THE 1456Z NESDIS SATELLITE PRECIPITATION
ESTIMATE...IS SHOWING INDICATIONS OF SPREADING FURTHER TO THE
NORTH AND PERHAPS INLAND INTO SOUTHERN LA.  REGARDLESS...THE
STRENGTH OF THE LOW LEVEL INFLOW AND ANOMALOUSLY MOIST
PROFILES...WITH ABOVE FREEZING TEMPERATURES EXTENDING UP TO 4.5-5
KM AGL...WILL ENCOURAGE EFFICIENT WARM RAIN PROCESSES AND LOCALLY
HEAVY AMOUNTS.  THIS WAS EVIDENCED ACROSS SOUTHEASTERN LA THIS
MORNING WHERE 1-2 INCH/HR RAINFALL RATES WERE OBSERVED ALONG A
TRAINING BAND THAT SET UP ACROSS THE REGION. ALSO...FLASH FLOOD
GUIDANCE VALUES HAVE DECREASED ACROSS MUCH OF THE REGION THIS
MORNING...SUGGESTING THE THRESHOLD FOR FLASH FLOODING HAS COME
DOWN AS WELL.

THE HI-RES MODEL CONSENSUS CONTINUES TO SHOW THE HEAVIEST AMOUNTS
CENTERING ACROSS SOUTHERN LA COINCIDING WITH MARGINALLY BETTER
INSTABILITY AND THE ENHANCED LIFT AFFORDED BY A COASTAL SURFACE
FRONT.  THE LATEST RUNS OF THE HRRR AS WELL AS THE 00Z HRW-ARW
SHOW WIDESPREAD ADDITIONAL AMOUNTS OF 1-2 INCHES ACROSS
SOUTH-CENTRAL LA...WITH LOCAL AMOUNTS  OF 2-4 INCHES THROUGH 21Z. 
FURTHER TO THE NORTH...A SLOW MOVING NORTHERN STREAM BOUNDARY
EXTENDING BACK INTO THE LOWER MS VALLEY...MAY HELP TO EXPAND THE
HEAVY RAINFALL THREAT UP INTO PORTIONS OF THE SOUTHWESTERN MS.

PEREIRA

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

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

LAT...LON   31739174 31539123 30919109 30279093 29759038 
            29159017 28989086 29439175 29449251 29599316 
            29569367 30249362 30819280 31359233