MESOSCALE PRECIPITATION DISCUSSION 0161...CORRECTED
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
328 PM EDT SAT APR 29 2017

CORRECTED FOR TYPO IN SECOND PARAGRAPH

AREAS AFFECTED...WESTERN AND NORTHWEST LA INTO S-CNTRL AR

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

VALID 291925Z - 292300Z

SUMMARY...A COMPLEX OF THUNDERSTORMS OVER WESTERN AND NORTHWEST LA
WILL PRODUCE LOCAL HOURLY RAIN RATES AS HIGH AS 2-2.5" WHICH COULD
CAUSE SOME LOCALIZED FLASH FLOODING OVER THE NEXT FEW HOURS.

DISCUSSION...A CONVECTIVE COMPLEX ONGOING OVER WESTERN LA AS OF
19Z...IS IN A REGION OF LOW LEVEL SOUTHERLY FLOW OF 30-45 KT AND
WITHIN A VERY MOIST UNSTABLE ENVIRONMENT. PRECIPITABLE WATER
VALUES ARE GENERALLY 1.5-1.75" AND DEW POINTS ARE IN THE UPPER 60S
TO MID 70S WITH MUCAPE 3000-4000 J/KG. THOUGH HAIL CONTAMINATION
MAY BE A FACTOR...KPOE DUAL POL RADAR SHOWED LOCAL HOURLY RAIN
RATES AS HIGH AS 3" OVER SABINE PARISH ENDING AROUND 19Z.

SIMILARLY HIGH RAIN RATES SHOULD CONTINUE FOR THE NEXT FEW HOURS
AS STRONG AND VERY MOIST SOUTHERLY FLOW PERSISTS AND THE AIR MASS
REMAINS VERY UNSTABLE. WHILE A SUPERCELL WITHIN THE CONVECTIVE
COMPLEX OVER NATCHITOCHES PARISH SHOULD CONTINUE TO TRACK OFF
TOWARD THE NORTHEAST...SIGNS OF REGENERATION/BACK-BUILDING ARE
EVIDENT NEAR THE SABINE RIVER. GIVEN KINEMATIC PROFILES SUPPORT
TRAINING AND BACK-BUILDING...LOCAL 3-HOURLY RAINFALL TOTALS OF
2.5-4" APPEAR LIKELY AS THE COMPLEX MOVES SLOWLY NORTH-NORTHEAST
INTO A REGION OF 3-4" 3-HOUR FFG VALUES IN WESTERN AND NORTHWEST
LA INTO S-CNTRL AR. LOCALIZED FLASH FLOODING IS POSSIBLE AS A
RESULT. SOME UNCERTAINTY WITH DRY AIR ENTRAINMENT AND POOR MODEL
HANDLING REDUCES CONFIDENCE BEYOND 23Z.

MCDONNAL/OTTO

ATTN...WFO...LCH...LZK...SHV...

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

LAT...LON   33379283 33339244 33059220 32569216 31819233
            31169283 31119355 31289382 31559390 31969386
            32359385 32849370 33299326