MESOSCALE PRECIPITATION DISCUSSION 0034
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
246 PM EST TUE FEB 23 2016
 
AREAS AFFECTED...S LOUISIANA...S MISSISSIPPI 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 231946Z - 232346Z
 
SUMMARY...ISOLATED RISK FOR FLASH FLOODING WITH CELL MERGERS AND
SHORT TERM TRAINING

DISCUSSION...CONVENTIONAL GOES-EAST SATELLITE IMAGERY SHOWS THE
WELL DEVELOPING CUT-OFF LOW ACROSS NE TX.
HIGHLY DIFFLUENT FLOW BETWEEN THE MID TO UPPER POLAR JET CURVING
NORTH WHILE SLIGHTLY HIGHER FLOW OF THE SOUTHERN STREAM IS
ACCELERATING EASTWARD ALONG THE GULF COAST. UPSTREAM JET ENERGY
WILL CONTINUE TO INCREASE UPPER LEVEL FLOW TO OVER 120 KTS IN THE
EVENING PERIOD FOR CONTINUED STRONG ASCENT. AT THE
SURFACE...SIGNIFICANT HEIGHT FALLS SUPPORT STRENGTHENING
ISALLOBARIC SOUTHERLY FLOW FOR STRONG MOISTURE FLUX ALONG SW-NE
FRONTAL ZONE ACROSS S LA INTO S MS ATTM.  CONVECTION ALONG AND
SOUTH OF THE FRONTAL ZONE WILL CONTINUE TO BECOME MORE EFFICIENT
WITH TIME AND WITH TPWS OVER 1.5" AND HIGH FLUX ON 50 KT 850 SLY
FLOW PER TMSY VAD...RATES IN EXCESS OF 2.0"/HR ARE POSSIBLE.  ONLY
LIMITING FACTOR APPEARS TO BE THE DURATION TO EXCEED THE VERY HIGH
FFG VALUES ACROSS S LA AND S MS...THIS MAY BE ALLEVIATED LOCALLY
DUE TO SOME ISOLATED TRAINING OF CONVECTION ALONG THE FRONTAL
BOUNDARY THAT IS FAIRLY WELL ORIENTED WITH RECENT RAP MEAN CELL
MOTION VECTORS.  THOUGH NOT AS LIKELY THE UPPER LEVEL JET SPLIT
WITH UPSTREAM ENERGY CAN PRESENT A FAVORABLE ENVIRONMENT FOR
BACKBUILDING CELLS...THOUGH OVERALL FORWARD PROGRESS OF THE SYSTEM
AS A WHOLE SHOULD LIMIT THE OVERALL TIME UPSTREAM DEVELOPMENT
WOULD SUPPORT TRAINING AT ANY GIVEN LOCATION IN THE SHORT TERM. 
CURRENTLY THINKING BEST SET UP IS ALONG THE LINE FROM WESTERN
VERMILLION BAY TOWARD WASHINGTON PARISH THROUGH THE NEXT FEW HOURS
BEFORE A GENERAL EASTWARD SHIFT BEGINS TO AFFECT S MS COUNTIES
TOWARD 00Z. 
THIS SCENARIO IS BEST SUPPORTED BY THE RECENT HRRR AND ESRL EXP.
HRRR RUNS...SUGGESTING TOTALS IN THE 2-4" RANGE FOR ISOLATED FFG
EXCEEDANCE.  

GALLINA

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

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

LAT...LON   31718972 31618905 31218880 30618882 30378902 
            29838952 29249027 29139084 29279170 29539242 
            29849277 30219286 30809164 31399066