MESOSCALE PRECIPITATION DISCUSSION 0559
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
100 PM EDT SAT AUG 13 2016
 
AREAS AFFECTED...CENTRAL/SOUTHERN LA...FAR SOUTHWEST MS 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 131700Z - 132300Z
 
SUMMARY...EXTREMELY HEAVY RAINFALL WILL CONTINUE THROUGH THE
AFTERNOON...WITH DANGEROUS AND POTENTIALLY LIFE-THREATENING FLASH
FLOODING EXPECTED.

DISCUSSION...A VERY SLOW-MOVING LOW CENTER IS NOW SITUATED JUST
WEST OF ALEXANDRIA LA AND CONTINUES TO DRIFT WESTWARD. VERY HEAVY
CONVECTIVE RAINS CONTINUE TO DEVELOP AND FOCUS OVER PORTIONS OF
CENTRAL AND SOUTHWEST LA AROUND THE SOUTHWEST FLANK OF THE LOW
CENTER.

THE ACTIVITY AGAIN IS BEING GREATLY ENHANCED BY THE PRESENCE
CONFLUENT LOW LEVEL FLOW AND ADVECTION OF DEEP TROPICAL MOISTURE
AND A MODERATE TO STRONG LEVEL OF INSTABILITY IN OFF THE NORTHWEST
GULF OF MEXICO AND ADJACENT AREAS OF SOUTHEAST TX. MLCAPE VALUES
ARE AS HIGH AS 2000 TO 3000 J/KG JUST OFF THE SOUTHEAST TX COAST.
MEANWHILE...THE LATEST BLENDED-TPW PRODUCT AND GPS DATA SHOWS
PWATS IN EXCESS OF 2.5 INCHES WITHIN THE BROADER LOW CIRCULATION.

MOVING THROUGH THE AFTERNOON HOURS...THE BEST FORCING SHOULD
REMAIN AROUND THE SOUTHWEST FLANK OF THE LOW CIRCULATION AND THIS
WOULD FAVOR PORTIONS OF SOUTHWEST LA IN PARTICULAR SEEING
ADDITIONAL EXTREMELY HEAVY RAINFALL. TRAINING CONVECTIVE BANDS
WITH HOURLY RAINFALL RATES OF UP TO 3 INCHES/HR WILL FAVOR VERY
ADDITIONAL HIGH RAINFALL TOTALS THROUGH LATE AFTERNOON.

AS PER THE LATEST HRRR/HRRP GUIDANCE...EXPECT ADDITIONAL RAINFALL
AMOUNTS OF 4 TO 8 INCHES OVER PORTIONS OF SOUTHWEST LA WITH A
FOCUS GENERALLY JUST EAST OF THE LAKE CHARLES AREA. LESSER AMOUNTS
OF 2 TO 4 INCHES ARE EXPECTED FARTHER EAST AND CLOSER INTO THE
BATON ROUGE...LAFAYETTE AND NEW IBERIA AREAS WHICH HAVE ALREADY
BEEN VERY HARD HIT BY FLASH FLOODING.

DANGEROUS AND POTENTIALLY LIFE-THREATENING FLASH FLOODING WILL
REMAIN LIKELY GIVEN THE ADDITION OF THESE VERY HEAVY RAINS AND
ESPECIALLY OVER AREAS OF SOUTH-CENTRAL LA WHERE STORM TOTALS ARE
BEGINNING TO EXCEED 25 INCHES FOR THE EVENT IN SOME AREAS.

ORRISON

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

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

LAT...LON   31669121 31539072 31079044 30479037 29709072 
            29429127 29399210 29609326 30039366 30759364 
            31169338 31259312 31069256 31019194 31139160