MESOSCALE PRECIPITATION DISCUSSION 0923
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
351 PM EDT WED NOV 01 2017

AREAS AFFECTED...SOUTHWEST TO SOUTH-CENTRAL LA

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

VALID 011950Z - 020030Z

SUMMARY...A TRAINING AXIS OF HEAVY SHOWERS AND THUNDERSTORMS WILL
FOSTER SOME FLASH FLOODING POTENTIAL OVER THE NEXT SEVERAL HOURS.

DISCUSSION...A RATHER WELL-DEFINED SOUTHERN STREAM SHORTWAVE
TROUGH CONTINUES TO ADVANCE EAST ACROSS THE CENTRAL GULF COAST
STATES THIS AFTERNOON...WITH THE SOUTHWEST FLANK OF THIS ENERGY
HELPING TO FOSTER AN AXIS OF COLD-TOPPED CONVECTION WHICH OVER THE
LAST COUPLE OF HOURS HAS GROWN IN ORGANIZATION AND HAS BEEN
EXHIBITING INCREASED TENDENCIES FOR BACKBUILDING AND TRAINING.

THE CONVECTION IS FORMING IN A VERY MOIST ENVIRONMENT AIDED BY
CONFLUENT LOW LEVEL FLOW AND ENHANCED BY DIVERGENT FLOW ALOFT
ASSOCIATED WITH THE AFOREMENTIONED SHORTWAVE TROUGH. THERE IS A
FAIRLY SUBSTANTIAL POOL OF INSTABILITY AS WELL FOCUSED FROM THE
UPPER TX COAST EAST INTO MUCH OF SOUTHWEST LA AND ADJACENT AREAS
OF THE NORTHWEST GULF OF MEXICO. SOUTHWEST LOW LEVEL FLOW
ADVANCING NORTHEAST INTO THE GENERAL VICINITY OF SOUTH-CENTRAL LA
HAS FOSTERED A NOTABLE AXIS OF INSTABILITY TRANSPORT INTO AN AREA
OF FAVORABLE DEEP LAYER SHEAR AND FORCING WHICH HAS THUS
FACILITATED A CONDUCIVE ENVIRONMENT FOR BACKBUILDING CONVECTION.

ALREADY AS MUCH AS 3 TO 4 INCHES OF RAIN HAS FALLEN OVER PARTS OF
SOUTH-CENTRAL LA...AND ESPECIALLY AROUND THE LAFAYETTE AREA. THE
LATEST HRRR AND HRRRX GUIDANCE GENERALLY APPEARS TO HAVE THEIR
RESPECTIVE CONVECTIVE AXIS ALIGNED A TAD TOO FAR NORTH. THE 12Z
NSSL-WRF ACTUALLY APPEARS TO HAVE THE BEST HANDLE OF THE ONGOING
ACTIVITY...AND SUGGESTS ADDITIONAL AMOUNTS OF AS MUCH AS 3 TO 4
INCHES LOCALLY THROUGH 00Z ACROSS SOUTH-CENTRAL LA IN A GENERAL
WEST/EAST AXIS. SOME FLASH FLOODING WILL BE POSSIBLE GIVEN THESE
ADDITIONAL TOTALS. WILL CONTINUE TO MONITOR.

ORRISON

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

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

LAT...LON   30649125 30479076 30099067 29849111 29709230
            29799294 30039321 30409307 30629241