MESOSCALE PRECIPITATION DISCUSSION 0546
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
300 PM EDT THU AUG 11 2016
 
AREAS AFFECTED...SOUTHERN MS...SOUTHEAST AND CENTRAL LA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 111900Z - 120030Z
 
SUMMARY...UPGRADE OF EXCESSIVE RAINFALL OUTLOOK TO HIGH RISKED
BASED ON INCREASED DAYTIME HEATING, VERY HIGH MOISTURE AND SLOW
CELL MOTIONS SHOULD POSE FLASH FLOODING CONCERNS ACROSS S MS/SE LA
THROUGH THE EARLY EVENING HOURS.

DISCUSSION...CLEAR SKIES NORTH OF I-10 ACROSS LA INTO S MS HAVE
ALLOWED FOR SFC T TO RISE INTO THE UPPER 80S TO MID
90S...COINCIDENT WITH TDS IN THE MID TO UPPER 70S...REPLENISHING
THE INSTABILITY.  GOES-E VISIBLE IMAGERY SHOWS THE APEX OF THE LOW
LEVEL TROF NORTH OF KJAN STARTING TO ALIGN WITH MID TO UPPER LEVEL
SHORTWAVE VORT CENTER...THIS IS CURRENTLY PROVIDING INCREASED
UPPER LEVEL ASCENT AS WELL AS LOWER LEVEL CONVERGENCE TO SUPPORT
INCREASED CONVECTIVE GROWTH OVER THE NEXT FEW HOURS.  THE MAIN
HUB/UPPER LEVEL PIVOT REMAINS FURTHER E ALONG THE MS/AL COASTAL
BORDER WITH SLOW DRIFT WHILE 200-250MB OUTFLOW CHANNEL IS PRESENT
WITH THE ENTRANCE REGION ACROSS SE LA.  THIS WILL CONTINUE TO
PROVIDE EXCELLENT EVACUATION PARTICULARLY GIVEN THE DIFFLUENCE
WITH NICELY SHAPED ANTICYCLONIC LOOK.  CONVECTION NEAR THIS
SOUTHWARD MOVING VORT/CONVERGENCE ZONE WILL BE HIGHLY EFFICIENT
THROUGH A GENERALLY DEEP LAYER...GIVEN SATURATED PROFILES WITH
TPWS OVER 2.5" IN THE AREA OF GREATEST CONCERN (SE LA/NORTH OF
I-10/S MS) RATES IN EXCESS OF 2-2.5" ARE LIKELY AND WITH STRONG
FLUX/MERGERS...WOULD NOT BE SURPRISED OF 1HR TOTALS OVER 3"
POSSIBLE IN ISOLATED SPOTS.  OVERALL THE SLOW CELL MOTIONS DUE TO
PROXIMITY TO UPPER LEVEL HUB SHOULD ALLOW FOR SOME VERY HIGH
TOTALS AND PRESENT LIKELY FLASH FLOODING CONDITIONS THOUGH
SUNSET...AS CONVECTIVE VIGOR WILL WANE AS INSTABILITY FROM DAYTIME
HEATING IS EXHAUSTED.  

FURTHER WEST ACROSS CENTRAL LA...AN OUTER BAND IS BEGINNING TO
DEVELOP ACROSS THE REGION WHILE THE STATIONARY OLDER CONFLUENCE
BAND FURTHER SOUTH CONTINUES TO REMAIN FED BY LOW LEVEL
CONVERGENCE OUT OF NE TX.  EVENTUALLY THE NEWER CONVECTIVE BAND
WILL BE DROP SOUTHWARD AND MELD WITH THE OLDER BAND KEEPING A
THREAT OF INCREASED DURATION/COMPOUNDING TOTALS ACROSS THIS AXIS
THROUGH NIGHT FALL AS WELL.  

GALLINA

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

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

LAT...LON   32669032 31458887 30448882 29968914 29838971 
            29789109 30079199 30699294 31209330 32159357 
            32539232 31819158 32039116