MESOSCALE PRECIPITATION DISCUSSION 0523
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
902 PM EDT SUN SEP 27 2015
 
AREAS AFFECTED...PORTIONS OF THE CENTRAL GULF COAST 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 280100Z - 280500Z
 
SUMMARY...CONVECTION WITH HEAVY RAIN MOVING ACROSS PORTIONS OF
SOUTHERN MS/SOUTHWEST AL AND THE WESTERN FL PANHANDLE COULD RESULT
IN FLASH FLOODING.

DISCUSSION...THE CORE OF THE STRONGEST CONVECTION PRODUCING FLASH
FLOODING ACROSS SOUTHEAST MS/SOUTHWEST AL (WHERE 4-7 INCHES OF
RAINFALL WAS OBSERVED) HAS WEAKENED AS IT CROSSED SOUTHWEST AL
EARLY THIS EVENING. CLOUDS TOP ARE WARMING (PER THE LATEST IR LOOP
IMAGES)...AND THE KMOB RADAR SHOWED HOURLY RAINFALL RATES DROPPING
BELOW 2 INCHES. 

THE LOW LEVEL INFLOW IS FORECAST TO REMAIN BETWEEN 20 TO 25
KNOTS...AND INSTABILITY SHOULD REMAIN MARGINALLY SUFFICIENT FOR
ADDITIONAL CONVECTIVE DEVELOPMENT. REGIONAL RADARS SHOWED TWO
DISTINCT AREAS OF INFLOW. THE FIRST WAS ANCHORED IN THE LOW LEVEL
EAST SOUTHEAST FLOW...SENDING ADDITIONAL CONVECTION INTO SOUTHWEST
AL. THE SECOND WAS TRACKING NORTH IN THE MID LEVEL FLOW AHEAD OF
THE CLOSED SYSTEM OVER THE WESTERN GULF OF MEXICO. 

THE CONVERGENCE OF THE INFLOWS WILL RESULT IN ADDITIONAL
CONVECTION CROSSING AREAS THAT RECEIVED VERY HEAVY RAINFALL
EARLIER. IT SHOULD BE NOTED THAT MOST THE LATEST HIGH RESOLUTION
GUIDANCE (INCLUDING THE 22Z HRRR/RAP AND 12Z WRF ARW/NMMB) HAD THE
CONVECTION THAT IS OCCURRING OVER SOUTHWEST AL OVER SOUTH CENTRAL
MS. THUS...THE HIGH RESOLUTION GUIDANCE HAS NOT BEEN HELPFUL FOR
PLACING THE HEAVIEST RAINFALL AND FLASH FLOOD POTENTIAL THROUGH
THE LATE EVENING HOURS.

BASED ON THE DEEP MOISTURE IN PLACE (WITH PRECIPITABLE WATER
VALUES REMAINING NEAR 2.00 INCHES)...PERSISTENT INFLOW AND
INSTABILITY OVER THE GULF OF MEXICO SOUTH OF MS/AL/WESTERN
FL...ADDITIONAL CONVECTION COULD PRODUCE 2 INCHES OF RAINFALL IN
PLACES THAT EXPERIENCED FLASH FLOODING EARLIER. THE ADDITIONAL
HEAVY RAINFALL COULD RESULT IN ADDITIONAL FLASH FLOODING.

HAYES

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

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

LAT...LON   32248821 32038761 31488719 31038702 30798699 
            30358702 30148757 30138767 30128776 30168831 
            30248879 30498895 30938901 31498900 31658889 
            32148871