MESOSCALE PRECIPITATION DISCUSSION 0001
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
906 PM EST THU FEB 20 2014
 
AREAS AFFECTED...PORTIONS OF SOUTHEAST LA AND SOUTHERN MS 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 210205Z - 210605Z
 
SUMMARY...A LARGE CLUSTER OF THUNDERSTORMS IS BEGINNING TO TRAIN
ALONG AND NORTHEAST OF AN OUTFLOW BOUNDARY JUST SOUTH OF THE LA/MS
BORDER.  HIGH PRECIPITATION EFFICIENCY AND MINIMAL PROPAGATION
OVER THE NEXT FEW HOURS SHOULD LEAD TO FLASH FLOODING.

DISCUSSION...PRECIPITABLE WATER VALUES OF AROUND 1.75 INCHES -- IN
THE 99TH PERCENTILE FOR MID TO LATE FEBRUARY -- EXIST WITHIN A
REGION AHEAD OF A COLD FRONT.  THE MOISTURE AVAILABILITY IS
LEADING TO PRECIPITATION EFFICIENCY NEAR THE LA/MS BORDER, WITH
HOURLY RAINFALL RATES OF 2-3" REPORTED BY THE SLIDELL LA WSR-88D. 
IT IS POSSIBLE THAT HAIL IS INFLATING RADAR ESTIMATES, SO THE BEST
GUESS IS THAT RAINFALL RATES OF 1-2" PER HOUR ARE OCCURRING. 
DIVERGENCE ALOFT IS EXCELLENT IN A SPLIT BETWEEN THE POLAR AND
SUBTROPICAL H2 JETS.  EARLIER CONVECTION HAVE LEFT WHAT APPEARS TO
BE AN OUTFLOW BOUNDARY SOUTH OF THE EAST-WEST PORTION OF THE MS/LA
BORDER.  THE 01Z RAP INDICATES INFLOW AT 850 HPA INCREASES TOWARDS
50 KTS OVER THE NEXT COUPLE HOURS, BRINGING LOW-LEVEL SHEAR TO
35-40 KTS AND COULD LEAD TO BACKBUILDING AND SOME SLIGHT SOUTHWARD
PROPAGATION TO THE OUTFLOW BOUNDARY.  CORFIDI VECTORS BASED ON THE
18Z GFS IMPLY MINIMAL MOVEMENT TO THE ORGANIZED CONVECTIVE
ACTIVITY.  CAPE VALUES ARE EXPECTED TO REMAIN IN THE 1000-1500
J/KG RANGE PER THE 12Z ARW FOR THE NEXT SEVERAL HOURS.  THIS
COMBINATION OF INDICES IS FAVORABLE FOR WET MULTICELLS.  WITH NEW
ACTIVITY MOVING IN FROM THE ATCHAFALAYA SWAMP AND ANOTHER BATCH OF
THUNDERSTORMS MOVING INTO SOUTHWEST LA, BELIEVE THE REGION SHOULD
SEE REGIONAL FLASH FLOODING THROUGH 06Z.

ROTH

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

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

LAT...LON   31818909 32048989 31549127 30829179 30429146 30519028
            30948925 31558892 31818909