MESOSCALE PRECIPITATION DISCUSSION 0296
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
409 PM EST SUN DEC 22 2013
 
AREAS AFFECTED...SE LA...SRN MS AND AL...NW FL 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 222108Z - 230208Z
 
SUMMARY...PERSISTENT CONVECTION IN THIS REGION WILL UNDERGO SUBTLE
ENHANCEMENT AS A MID LEVEL WAVE FOCUSES DEEPER ASCENT THROUGH MID
TO LATE EVENING. THE AXIS OF ENHANCED UPDRAFTS AND RAINFALL
INTENSITY WILL MIGRATE VERY SLOWLY EASTWARD. FLASH FLOODING WILL
BECOME MORE LIKELY WHERE HEAVY RAIN HAD ALREADY FALLEN. A THREAT
OF FLASH FLOODING WILL ALSO SPREAD FARTHER EAST.

DISCUSSION...HAVING BEGUN EARLY THIS MORNING...AND LIKELY TO
PERSIST THROUGH MONDAY MORNING...THIS REGION WAS EXPERIENCING A
LONG DURATION RAIN EVENT WITHIN BROADLY CONVERGENT AND RELATIVELY
UNCHANGING LOWER TO MIDDLE LEVEL FLOW ON A LARGE SCALE. THE THREAT
OF FLASH FLOODING...AS OPPOSED TO AREAL FOODING/INUNDATION...WAS
TEMPERED SOMEWHAT BY SEASONALLY WEAK INSTABILITY. STILL...OBSERVED
RAIN RATES HAVE BEEN CAUSE FOR CONCERN AT TIMES. KMOB DUAL POL
RAINFALL ESTIMATES MATCHED VERY WELL WITH THE 2.35 INCHES OF RAIN
OBSERVED AT GULFPORT MS...WITH ESTIMATES OF GREATER THAN 4 INCHES
IN NEARBY AREAS. FLASH FLOOD GUIDANCE VALUES HAD PLUMMETED IN A
ZONE SOUTHWEST OF GULFPORT INTO SE LA...AND NORTHEASTWARD INTO
CENTRAL AL. THIS REGION WILL ALSO BE THE FIRST TO EXPERIENCE
ENHANCED RAIN RATES EARLY THIS EVENING.

NESDIS SPENES MESSAGE ALREADY DISCUSSED A SPEED MAX ACTING TO
ENHANCE CONVECTION OVER SE LA AS OF 21Z. IN ADDITION A LARGER
SCALE SHORTWAVE WILL BRUSH ACROSS THIS REGION BEGINNING THIS
EVENING AS IT MOVES FROM TEXAS UP TOWARD THE OHIO VALLEY
OVERNIGHT. A SLIGHT INCREASE TO LOW LEVEL CONVERGENCE AND MID
LEVEL ASCENT...COUPLED WITH THE WEAK HEATING CONTRIBUTION FROM THE
DIURNAL CYCLE OVER THE GULF INFLOW REGION...SHOULD YIELD DEEPER
UPDRAFTS AND MORE INTENSE RAIN RATES. HIGH RESOLUTION MODELING OF
RADAR REFLECTIVITY AND MEAN LAYER LOW LEVEL WINDS SUGGEST A VERY
SLOW EASTWARD ADVANCEMENT INITIATED BY THE WAVE COMING OUT OF
TEXAS...WITH EMPHASIS FOR LOCALLY HEAVY RAIN SHIFTING TOWARD SE
AL/NW FL AND PERHAPS SW GA OVERNIGHT.

BURKE

ATTN...WFO...TAE...BMX...MOB...JAN...LIX...LCH...

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

LAT...LON   29098666 28378828 28128995 28319157 28839205 29729153
            30729063 31658921 32188729 32058570 31558532 30648543
            29098666