MESOSCALE DISCUSSION 0943
   NWS STORM PREDICTION CENTER NORMAN OK
   0532 AM CDT FRI MAY 16 2008
   
   AREAS AFFECTED...SOUTHEAST LA
   
   CONCERNING...HEAVY RAINFALL 
   
   VALID 161032Z - 161330Z
   
   HEAVY CONVECTIVE RAINFALL RATES OF 1-2 INCHES PER HOUR ARE LIKELY TO
   PERSIST ACROSS PARTS OF SOUTHEAST LA EARLY THIS MORNING AS NORTH
   GULF MCS SPREADS NEWD ALONG STALLED FRONTAL ZONE BISECTING MS DELTA.
   
   
   DEEP-LAYER FRONTAL ZONE HAS STALLED WITHIN MODEST MEAN-LAYER WSWLY
   FLOW FROM THE WRN GULF NEWD ACROSS SERN LA EARLY TODAY. RECENT
   INCREASE IN DEEP CONVECTION ALONG THIS BOUNDARY COULD BE RELATED TO
   1) NOCTURNAL STRENGTHENING OF LLJ...AND/OR 2) LIFT WITH APPROACH OF
   MID/UPPER LEVEL WAVE/MCV ASSOCIATED WITH LARGE MCS OFF THE TX/LA
   GULF COAST. TPW IMAGERY FROM CIRA INDICATES A PW PLUME WITH VALUES
   AOA 2 INCHES ACROSS THE REGION. THIS RICH MOISTURE WAS LIKELY
   CONTRIBUTING TO EXCESSIVE RAINFALL RATES WITH OVER 2 INCHES PER HOUR
   RECENTLY OBSERVED IN NEW ORLEANS.
   
   WEAK LARGE SCALE HEIGHT FALLS WILL FURTHER AID LOW LEVEL CONVERGENCE
   AND LIFT ALONG THE FRONTAL ZONE THROUGH THIS MORNING. IN
   ADDITION...GENERALLY WEAK FORWARD PROPAGATION VECTORS ACROSS THE NRN
   GULF SUGGEST ONGOING MCS ACTIVITY WILL HAVE SOME TENDENCY TO
   BACKBUILD BEFORE THE ENTIRE COMPLEX MOVES THROUGH LATER THIS
   MORNING. LATEST HIREZ WRF-ARW APPEARS TO DEPICT BOTH THE FRONTAL
   CONVECTION AND THE GULF MCS WELL. ONGOING HEAVY RAINFALL OCCURRING 
   ALONG THE FRONTAL BAND WILL ONLY BE EXACERBATED AS ANOTHER ROUND OF
   HEAVY RAIN ACCOMPANIES THE MCS MOVING ACROSS THE SAME AREAS LATER
   THIS MORNING.
   
   ..CARBIN.. 05/16/2008
   
   
   ATTN...WFO...LIX...LCH...
   
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