MESOSCALE PRECIPITATION DISCUSSION 0028...CORRECTION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
927 AM EDT THU MAY 02 2013
 
AREAS AFFECTED...SOUTHERN MS AND SOUTHERN AL 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 021309Z - 021909Z
 
SUMMARY...NEW THUNDERSTORM ACTIVITY IS DEVELOPING WITHIN AN AREA
WHICH RECEIVED SIGNIFICANT RAINS OVERNIGHT, WHICH WILL LEAD TO
FLASH FLOODING THIS MORNING INTO EARLY THIS AFTERNOON.

DISCUSSION...RECENT RADAR IMAGERY SHOWS A SMALL REDEVELOPING BAND
OF CONVECTION ACROSS SOUTHERN MS OVER AREAS DELUGED DURING THE
PAST 18 HOURS, WHICH PREVIOUSLY DROPPED THREE-HOUR FLASH FLOOD
GUIDANCE (FFG) VALUES UNDER AN INCH.  THE SYNOPTIC AND MESOSCALE
PATTERN IS TRICKY IN THIS REGION, AS THE BEST LOW-LEVEL
CONVERGENCE LIES ALONG AN INVERTED TROUGH ACROSS SOUTHEAST LA AND
SOUTHWEST MS, WHERE IT IS EXPECTED TO PERSIST INTO THIS AFTERNOON.
 HOWEVER, A DEEP-LAYERED LOW NEAR THE MOUTH OF THE MS RIVER IS
EXPECTED TO SHIFT EASTWARD INTO THE NORTHERN GULF OF MEXICO, WHICH
FORCES THE BETTER DIVERGENCE ALOFT OVER SOUTHERN MS AND SOUTHERN
AL AND OUT OF SOUTHEAST LA WITH TIME.  PROPAGATION/ CORFIDI
VECTORS COUNTER THE LOW-LEVEL FLOW, ENHANCING THE THREAT FOR
TRAINING/STALLED CONVECTIVE CELLS ACROSS THIS REGION TODAY. 
EXISTING PRECIPITABLE WATER (PW) VALUES ARE OVER 1.5 INCHES AND
THE BEST 850 HPA INFLOW IS A BIT TO THE NORTH OF THE COAST CLOSE
TO THE 32TH PARALLEL.  THE MESOSCALE GUIDANCE IS NOT AGREEABLE
WITH THEIR PRECIPITATION PLACEMENT, WITH THE 00Z NMM FOCUSING
ACTIVITY ALONG THE EAST-WEST PORTION OF THE LA/MS BORDER, WHILE
THE 09-11Z RAP FAVOR SOUTHERN AL.  KEEPING ALL THIS MIND, AND
ACCOUNTING FOR THE UNCERTAINTY, THE AREA WAS DRAWN TO ENCOMPASS AS
MANY FAVORABLE ATTRIBUTES TO FLASH FLOODING AS POSSIBLE.  LOCAL
RAINFALL AMOUNTS OF 2-4 INCHES ARE EXPECTED WITHIN A SHORT TIME
FRAME.

ROTH


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

LAT...LON   29008893 29909006 30989047 31859016 32238919 31778807
            30308786 29508810 29008893