MESOSCALE PRECIPITATION DISCUSSION 0025
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
421 PM EDT WED MAY 01 2013
 
AREAS AFFECTED...EASTERN LA...SOUTHERN MS 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 012020Z - 020020Z
 
SUMMARY...SLOW-MOVING CONVECTION WITH EMBEDDED CELL-MERGERS ARE
PROMOTING VERY HEAVY RAINFALL RATES WHICH WILL CONTINUE FOR THE
NEXT SEVERAL HOURS.

DISCUSSION...THE LATEST IR SATELLITE IMAGERY SHOWS COOLING
CONVECTIVE CLOUD TOPS OVER PORTIONS OF EASTERN LA AND INTO
SOUTHERN MS...WITH AREAS OF MERGING CONVECTIVE CELLS EMBEDDED
WITHIN WHAT IS A LARGER NW/SE AXIS OF BKN CONVECTION. THE COOLING
CLOUD TOPS SUGGESTS INCREASING RAINFALL RATES...AND THIS IS
ALREADY BEING CONFIRMED BY THE LATEST RADAR-BASED QPE.

EXPECTING AN INCREASE IN CONVECTIVE ORGANIZATION OVER THE NEXT
COUPLE OF HOURS AS DIURNAL HEATING AND ASSOCIATED SFC-BASED
INSTABILITY IS MAXIMIZED. IN PARTICULAR THE BEST FOCUS FOR
ORGANIZED CONVECTION SHOULD BE INVOF OF A SFC TROUGH AXIS
EXTENDING SOUTHEAST OF A LOW CENTER OVER N CNTRL LA AND DOWN TO
COASTAL AREAS OF SRN MS. ENHANCED SFC CONVERGENCE WILL BE OCCURING
ALONG AND JUST TO THE RIGHT OF THIS TROUGH...AND WITH SELY H85
FLOW EXPECTED TO INCREASE TO AOA 30 KTS BY 21Z...EXPECT THE
MOISTURE TRANSPORT TO FAVOR SUSTAINABLE AND SLOW-MOVING CONVECTION
AT LEAST UNTIL ABOUT SUNSET WHEN SFC-BASED INSTABILITY WILL BE
WANING. EXPECT RAINFALL RATES OF 1 TO 2 IN/HR...WITH STORM TOTALS
OF 3 TO 4 INCHES POSSIBLE. SOME OF THIS WILL BE FALLING OVER AREAS
THAT HAVE ALREADY SEEN HVY RAINS EARLIER IN THE DAY.
THEREFORE...FLASH FLOODING WILL BE POSSIBLE.

ORRISON 


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

LAT...LON   29528932 29898980 30649055 30929140 31149199 31509258
            31989289 32409270 32489194 32249076 31778957 30998853
            30318804 29728814 29468885 29528932