MESOSCALE PRECIPITATION DISCUSSION 285
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
828 AM EDT TUE MAY 30 2017

AREAS AFFECTED...SOUTHERN LA AND SOUTHERN MS

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

VALID 301227Z - 301727Z

SUMMARY...THUNDERSTORMS PRODUCING HEAVY RAINFALL RATES ARE
EXPECTED TO SPREAD INLAND ACROSS SOUTHERN LOUISIANA AND SOUTHERN
MISSISSIPPI THROUGH THE REMAINDER OF THE MORNING.  FLASH FLOODING
IS POSSIBLE WITH THE MOST PERSISTENT CONVECTION.

DESCRIPTION...REGIONAL RADARS INDICATE SLOW MOVING THUNDERSTORMS
PRODUCING RAINFALL RATES OF 2-3 INCHES PER HOUR MOVING INLAND FROM
THE NORTHERN GULF OF MEXICO.  THIS CONVECTION IS FORECAST TO
SPREAD FURTHER NORTHEAST OVER THE SOUTHERN THIRD OF LOUISIANA THIS
MORNING, WITH THE POTENTIAL FOR HEAVY RAINFALL RATES WITH A
PLETHORA OF DEEP MOISTURE ADVECTING NORTHWARD.  A STATIONARY
FRONTAL BOUNDARY NEAR THE COAST WILL PROVIDE A LIFTING MECHANISM
AND THUS ENHANCED MOISTURE CONVERGENCE. 

SURFACE DEW POINTS ARE IN THE MID TO UPPER 70S SOUTH OF THIS
BOUNDARY, WITH THE LATEST SPC MESOANALYSIS INDICATING PWS OF
NEARLY 2 INCHES APPROACHING THE COAST.   THE LATEST RAP MODEL
SHOWS PWS REMAINING NEAR 2 INCHES AS MOISTURE POOLS ALONG AND
SOUTH OF THIS FRONT AND REMAINS IN THIS GENERAL AREA THROUGH THE
REMAINDER OF THE MORNING HOURS. THE RAP AND SPC MESOANALYSIS ALSO
SHOW SURFACE BASED CAPES OF 2000-3000 J/KG OVER THE NEXT FEW HOURS
NEAR AND JUST INLAND FROM THE COAST.  THE 10Z HRRR SHOWS
ADDITIONAL RAINFALL ACCUMULATIONS OF LOCALLY 2 TO 4 INCHES WITHIN
THE HIGHLIGHTED AREA BY NOON TODAY, WITH ADDITIONAL HEAVY RAINFALL
POSSIBLE BEYOND THIS TIME PERIOD.  THIS IS ALSO SUPPORTED BY THE
00Z ECMWF WHICH INDICATES AREAS OF VERY HEAVY RAINFALL TODAY.

HAMRICK

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

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

LAT...LON   31268929 30978866 30458858 29538884 28918906
            28849023 28989109 29339178 29469262 29569327
            29719364 30299364 30639288 30909177 31219045