MESOSCALE PRECIPITATION DISCUSSION 0163
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
255 PM EDT SUN MAY 01 2016
 
AREAS AFFECTED...UPPER TX COAST...SOUTHWEST LA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 011855Z - 012245Z
 
SUMMARY...ADDITIONAL REPEATING SHOWERS AND THUNDERSTORMS POSSIBLE
THROUGH THIS AFTERNOON. GIVEN THE VERY WET ANTECEDENT
CONDITIONS...FLASH FLOODING WILL REMAIN A CONCERN.

DISCUSSION...A WELL-DEFINED AND CONVECTIVELY INDUCED OUTFLOW
BOUNDARY HAS BEEN SETTLING SLOWLY SOUTH OUT INTO THE IMMEDIATE
OFFSHORE WATERS OF SOUTHERN LA. HOWEVER...THE WESTERN END OF THIS
BOUNDARY EXTENDS BACK TO THE UPPER TX COAST. STRONG CONVECTION
CONTINUES TO FOCUS ALONG THE BOUNDARY AND ALSO IN AN ELEVATED
FASHION NORTH OF IT ALONG THE SOUTHERN LA COAST.

THE RAP MOISTURE FLUX CONVERGENCE IS A BIT STRONGER ALONG THE
UPPER TX COAST AND INTO SOUTHWEST LA...AND A NOSE OF MODERATE
INSTABILITY WITH MLCAPE VALUES OF 2000 TO 2500 J/KG ARE FOCUSING
IN ON THE WESTERN AND SOUTHWEST FLANK OF THE OUTFLOW BOUNDARY.
MEANWHILE...A SPLIT UPPER JET PATTERN REMAINS IN PLACE WITH
NOTABLY DIFFLUENT FLOW ALOFT PERSISTING AND HELPING TO SUSTAIN
STRONGER UPDRAFTS.

THE BULK OF THE STRONGER CONVECTION OVER THE NEXT FEW HOURS WILL
GENERALLY TEND TO FOCUS OVER THE OFFSHORE WATERS JUST SOUTH OF
LA...HOWEVER...THERE IS SUFFICIENT FORCING AND MOIST/UNSTABLE LOW
LEVEL FLOW INTERCEPTING AND OVERRUNNING THE BOUNDARY SUCH THAT
CONVECTION WILL TEND TO PERSIST A BIT LONGER OVER THE UPPER TX
COAST AND ADJACENT AREAS OF ESPECIALLY SOUTHWEST LA.

CONSEQUENTLY...THE THREAT FOR FLASH FLOODING CONTINUES HERE...WITH
RAINFALL RATES THAT MAY REACH OR EXCEED 2 INCHES/HR...AND YIELDING
ADDITIONAL AMOUNTS THROUGH THE LATE AFTERNOON OF 3 TO 6 INCHES. 

AREAS FARTHER DOWNSTREAM TOWARD SOUTHEAST LA SHOULD BECOME
STABILIZED ENOUGH FOR THE HEAVY RAINFALL THREAT TO GRADUALLY
DIMINISH AT LEAST FOR THE MID TO LATE-AFTERNOON HOURS AS THE MAIN
CONVECTIVE FOCUS WILL SHIFT FARTHER SOUTH AND EAST AND OUT OVER
THE WATER.

ORRISON

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

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

LAT...LON   30319233 29899135 29549115 29239135 29259196 
            29519299 29599378 29509448 29389485 29609502 
            30039445 30279376