MESOSCALE PRECIPITATION DISCUSSION 0305
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
820 AM EDT SUN JUL 05 2015
 
AREAS AFFECTED...PORTIONS OF THE LOWER MISSISSIPPI VALLEY INTO SRN
MISSISSIPPI/ALABAMA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 051218Z - 051745Z
 
SUMMARY...PERIODS OF TRAINING CONVECTION MAY LEAD TO A FEW FLASH
FLOODING CONCERNS FROM SERN ARKANSAS/NERN LOUISIANA INTO SRN
MISSISSIPPI/ALABAMA THROUGH 18Z. THE THREAT DOES NOT APPEAR TO BE
WIDESPREAD IN NATURE.

DISCUSSION...SATELLITE AND RADAR TRENDS OVER THE PAST HOUR OR SO
HAVE SHOWN INCREASING COVERAGE OF CONVECTION OVER PORTIONS OF SERN
ARKANSAS INTO LOUISIANA...WITH DUAL POL RADAR ESTIMATED RAINFALL
RATES OF 1-2 IN/HR. THE ACTIVITY SEEMS TO BE PARTIALLY TIED TO A
SOMEWHAT ELONGATED AND DISORGANIZED UPPER LEVEL VORTICITY MAX
APPROACHING NRN LOUISIANA FROM THE OKLAHOMA/ARKANSAS
BORDER...NOTED ON WATER VAPOR IMAGERY AND IN RAP MODEL GUIDANCE. 

WHILE LOW LEVEL FLOW WAS ONLY 20 KTS OR SO ACROSS THE REGION AND
LOW LEVEL CONFLUENCE ACROSS SRN MISSISSIPPI/ALABAMA IS EXPECTED TO
WEAKEN INTO THE LATE MORNING HOURS...MEAN STORM MOTIONS ARE ALSO
ROUGHLY 20 KTS TOWARD THE EAST WHICH MAY PROMOTE PERIODS OF
TRAINING. FLOW ALOFT WAS DIFFLUENT ALOFT...MOST NOTABLY ACROSS THE
LOUISIANA/MISSISSIPPI BORDER WHICH MAY HELP TO ENHANCE VERTICAL
MOTIONS AS INSTABILITY GROWS WITH THE ONSET OF DAYTIME HEATING. 

HI-RES MODEL GUIDANCE IS A MIXED BAG WITH REGARD TO HEAVY
RAIN...BUT AN AXIS OF 3-5 INCHES IS NOTED IN THE 00Z HRW-ARW...06Z
NAM CONEST...00Z NSSL WRF FROM SERN ARKANSAS/NERN LOUISIANA INTO
W-CNTRL MISSISSIPPI. RECENT RUNS OF THE HRRR AND EXPERIMENTAL HRRR
ALSO SHOW THESE HEAVY AMOUNTS BUT ON A MORE LOCALIZED BASIS
THROUGH 18Z. GIVEN FLASH FLOOD GUIDANCE OF ANYWHERE BETWEEN 2-4
INCHES IN 3 HOURS ACROSS THE REGION...SOME LOCATIONS MAY
EXPERIENCE FLASH FLOOD CONCERNS.

OTTO

ATTN...WFO...BMX...JAN...LIX...LZK...MOB...SHV...

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

LAT...LON   33979174 33639083 32798951 32388767 31898720 
            31188720 30928792 30828945 31029093 31739190 
            32489250 33459290 33969258