MESOSCALE PRECIPITATION DISCUSSION 0091...CORRECTED
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
454 PM EDT FRI APR 06 2018

CORRECTED FOR UPDATE TO GRAPHIC

AREAS AFFECTED...NORTHEAST TX...SOUTHEAST OK...SOUTHERN
AR...NORTHERN LA...CENTRAL/SOUTHERN MS...WEST-CENTRAL AL

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

VALID 062050Z - 070250Z

SUMMARY...AN EXPANSIVE AXIS OF SHOWERS AND THUNDERSTORMS WILL
CONTINUE WELL THROUGH THE EVENING HOURS AND WILL TEND TO ORGANIZE
FURTHER SOUTH OVER THE NEXT FEW HOURS. HEAVY RAINFALL RATES TO
NEAR 2 INCHES/HR AND CONCERNS OVER CELL-TRAINING WILL LEAD TO
CONCERNS FOR FLASH FLOODING.

DISCUSSION...LATE-AFTERNOON GOES-16 1-MINUTE VISIBLE SATELLITE
IMAGERY SUGGESTS A VERY UNSTABLE BOUNDARY LAYER FOCUSED ACROSS
NORTHEAST TX AND AREAS EAST ACROSS CENTRAL/NORTHERN LA WHERE A
NOTABLY AGITATED CU FIELD IS SEEN. MEANWHILE...THE MID LEVEL WV
IMAGERY SHOWS A VERY WELL-DEFINED SHORTWAVE TROUGH AND ASSOCIATED
VORT CENTER EJECTING ACROSS THE SOUTHERN PLAINS.

ALREADY AN EXPANSIVE AXIS OF COLD-TOPPED CONVECTION IS IMPACTING
AREAS OF SOUTHEAST OK...SOUTHERN AR AND NORTHERN MS ALONG AND
NORTH OF A WAVY STATIONARY FRONT GIVEN THE PERSISTENT WARM
ADVECTION PATTERN AHEAD OF THE SHORTWAVE TROUGH...BUT THIS
CONVECTIVE AXIS WILL BEGIN TO DROP SOUTH AND EXPAND IN COVERAGE
OVER THE WARM SECTOR THROUGH THE EVENING HOURS.

THE LATEST RAP ANALYSIS SHOWS A POOL OF MLCAPE VALUES OF 2000 TO
3000 J/KG OVER NORTHEAST TX AND NORTHWEST LA ALREADY ALONG WITH
PROXIMITY OF A VERY SHARP INSTABILITY THAT DELINEATES THE UNSTABLE
BOUNDARY LAYER FROM THE CONVECTIVELY REINFORCED COLD POOL JUST
NORTH OF THE FRONT. MEANWHILE...PWATS HAVE RISEN TO BETWEEN 1.4
AND 1.5 INCHES AND HAVE GRADUALLY BEEN FOSTERING HEAVIER RAINFALL
RATES.

OVER THE NEXT COUPLE OF HOURS AS THIS ENERGY CROSSES THE ARKLATEX
REGION...EXPECT A ROBUST EXPANSION OF CONVECTION FARTHER SOUTH
ACROSS NORTHEAST TX AND DOWN ACROSS NORTHERN LA AND THROUGH
CENTRAL MS AS IT INTERACTS WITH THIS UNSTABLE AIRMASS AND WITHIN A
RATHER STRONGLY SHEARED ENVIRONMENT THAT WILL FAVOR STRONG AND
ORGANIZED UPDRAFTS. AS PER RECENT SPC MCD #222...UPSCALE GROWTH IS
EXPECTED AND EVOLUTION INTO A QLCS IS POSSIBLE THIS EVENING.

EXPECT RAINFALL RATES OF UP TO 2 INCHES/HR AND A FAVORABLE
ENVIRONMENT FOR AT LEAST SOME PERIODIC TRAINING OF CONVECTIVE
CELLS NEAR THE FRONT. RAINFALL AMOUNTS THROUGH 03Z OF AS MUCH AS 3
TO 5 INCHES WILL BE POSSIBLE AND ESPECIALLY WHERE THE STRONGER
CONVECTIVE CORES AND CELL-TRAINING SETS UP. SOME FLASH FLOODING IS
POSSIBLE.

ORRISON

ATTN...WFO...BMX...FWD...JAN...LCH...LIX...LZK...MOB...OUN...
SHV...TSA...

ATTN...RFC...ABRFC...LMRFC...SERFC...WGRFC...

LAT...LON   34239552 34109426 33849281 33529118 33298942
            33158825 32588730 31498760 31088867 31008996
            31209146 31549322 32099459 32439530 32999598
            33729615