MESOSCALE PRECIPITATION DISCUSSION 0074
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1129 PM EST THU MAR 10 2016
 
AREAS AFFECTED...SE LOUISIANA...S MISSISSIPPI 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 110428Z - 110858Z
 
SUMMARY...FOCUS IN FORCING IN THE NEAR TERM LEADING TO FRACTURED
CONVECTION.  HOWEVER ENVIRONMENT FOR REPEAT ISENTROPIC EFFICIENT
RAINFALL PRODUCING CONVECTION SUPPORTS CONTINUED THREAT FOR
FLOODING ACROSS E LA/S MS. 

DISCUSSION...WV LOOP SHOWS NORTHERN S/W IS NOW WELL DISPLACED OUT
OF KY INTO WV WITH A WEAK WAVE INDUCED FROM THE CONVECTIVE COMPLEX
SHEARING ACROSS N AL AS WELL LEADING TO REDUCED FOCUS EXCEPT FOR
THE BROAD AREA OF STRONG SURFACE 25-30 KT FLOW ACROSS THE EASTERN
GULF WEST.  A BOUNDARY ESTABLISHED BY THE WEAK COLD POOL FROM
CONVECTION THROUGHOUT THE DAY CONTINUES TO FLATTEN E-W FROM DYING
CONVECTION ENTERING S AL ACROSS THE COASTAL COUNTIES OF MS INTO
EASTERN LA.  GIVEN THE ORIENTATION OF THE BOUNDARY AND CONTINUED
LARGE SCALE SOUTHERLY FLOW...ILL-FOCUSED/BROAD ISENTROPIC ASCENT
REMAINS LEADING TO FRACTURED CONVECTION.  GIVEN THE AMPLE MOISTURE
AND SOME SKINNY INSTABILITY PROFILES WITH MUCAPES IN THE 1000-1500
J/KG RANGE ACROSS SE LA THERE IS ENOUGH VIGOR TO KEEP THESE CELLS
GOING WITH RATES OF 1.0-1.25"/HR ON AVERAGE AND GIVEN REPEATING
NATURE ALONG WITH LITTLE MOVEMENT OF SOUTH...TOTALS HAVE BEEN
SUFFICIENT TO KEEP FLOODING A HIGH CONCERN ACROSS THE AREA
HIGHLIGHTED.  ADDITIONAL FRACTIONAL COVERAGE ACROSS SE LA MAY
INCREASE GIVEN SOME LOW LEVEL CONVERGENCE DUE TO COASTAL FRICTION
COMPONENT...POTENTIALLY SHIFTING THE FOCUS SOUTH TOWARD AREAS LESS
AFFECTED OVER THE LAST 3-4 HRS...WHICH COULD HELP THE PROLONGED
FLOODING SITUATION ALONG THE LA/MS BORDER.    

FURTHER SOUTH THE ISOLATED CONVECTION CAN BE SEEN BREAKING OUT
ALONG N-S COLD FRONTAL BOUNDARY THAT IS JUST A BIT E OF 94W THAT
WAS SEEN IN SWIR/IR LOOPS...ADDITIONAL DRYING ALOFT JUST WEST OF
THE FRONT IS EVIDENCE OF INCREASING JET STREAK THAT HAS ROUNDED
THE BASE TO PROVIDE ADDITIONAL ASCENT OVER THE NORTH WEST CENTRAL
GULF IN THE COMING HOURS.  THIS DRY AIR MIXING WILL ALLOW FOR
EASTWARD MOVEMENT OF THE BOUNDARY/COLD FRONT BUT THIS SHOULD
STRENGTHEN SURFACE CONVERGENCE FIELDS WITH THE 20-30KT SELY THAT
REMAINS QUITE MOIST OVER A DEEP LOW LEVEL DEPTH...WITH TPWS STILL
AT OR ABOVE 2.0".  BIGGEST QUESTION REMAINS THE TIMING OF THE
ACTIVATION AND APPROACH TO SHORE.  THE 12Z ARW HAD BEEN THE BEST
PERFORMING HI-RES CAM THROUGH 04Z...BUT ALSO STARTED BREAKING OUT
CONVECTION BY THIS TIME AS WELL OVER THE GULF AND WITH RECENT HRRR
RUNS BACKING OFF...SLOWING DOWN THERE INCREASING UNCERTAINTY TO
THE TIMING.

GALLINA

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

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

LAT...LON   31738903 31408849 30948845 30668838 30268842 
            29858932 29109009 29109085 29259127 29469191 
            29569226 29799245 30159244 30409228 30909140 
            31399057