MESOSCALE PRECIPITATION DISCUSSION 0215
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1148 AM EDT FRI JUL 18 2014
 
AREAS AFFECTED...CNTRL/SRN LOUISIANA INTO CNTRL/SRN MISSISSIPPI 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 181545Z - 182030Z
 
SUMMARY...VERY HEAVY RAINFALL RATES OF 2 TO 4 IN/HR ARE EXPECTED
TO CONTINUE NEAR AND SOUTH OF THE I-10 CORRIDOR ACROSS CNTRL AND
ERN LOUISIANA THROUGH THE EARLY AFTERNOON WITH WEAKENING LIKELY
AFTER 20Z. SLOW MOVEMENT AND REPEATING CELLS WILL CONTINUE THE
THREAT OF FLASH FLOODING.

DISCUSSION...AN ANOMALOUSLY MOIST AIRMASS IS IN PLACE OVER SERN
TEXAS INTO MUCH OF LOUISIANA CHARACTERIZED BY RECENT GROUND BASED
GPS PRECIPITABLE WATER VALUES OF 2.25 TO 2.75 INCHES...WHICH ARE
ABOVE THE 95TH PERCENTILE AND/OR NEAR THE 99TH PERCENTILE FOR
JULY. RAINFALL RATES OF 3.29 IN/HR AS OBSERVED FROM 13Z AT BPT AND
DUAL POL ZDR VALUES LARGELY LESS THAN 1.5 ARE INDICATIVE OF THE
TROPICAL AIRMASS IN PLACE ACROSS THE REGION. 

THERE ARE SEVERAL MESOSCALE CIRCULATIONS NOTED IN THE LATEST RADAR
IMAGERY WITH THE MOST PRONOUNCED OVER NRN ALLEN PARISH AT 15Z.
THESE CIRCULATIONS ARE EXPECTED TO TRACK EAST OVER THE NEXT FEW
HOURS WITH A CONTINUED CONFLUENT LOW LEVEL FLOW TRANSPORTING MOIST
GULF AIR NWD INTO LOUISIANA. THE HEAVIEST RAINFALL IS EXPECTED TO
OCCUR AHEAD OF THE MCV NOTED ABOVE...BUT ALONG THE SRN HALF OF THE
THREAT AREA WHERE THE GREATEST INSTABILITY IS PRESENT HELPING TO
SUPPORT HIGHER RAINFALL RATES. 

A LOWER FLASH FLOOD THREAT EXISTS ALONG THE WRN PORTION OF THE
THREAT AREA WHERE IT APPEARS HEAVY RAINFALL HAS ENDED FOR THE
TIMING BEING...BUT HEAVY RAINS FROM EARLIER THIS MORNING HAVE
SATURATED THE GROUND TO THE POINT WHERE ANY ADDITIONAL RAIN WILL
RESULT IN RUNOFF. WHILE RAINFALL RATES SHOULD BE LOWER ACROSS SWRN
MISSISSIPPI WITH LESS CAPE IN PLACE...ONGOING STEADY RAINFALL MAY
SET THE STAGE FOR A FEW FLASH FLOOD CONCERNS THROUGH THE EARLY
AFTERNOON.  

OTTO

ATTN...WFO...MOB...JAN...LIX...LCH...SHV...HGX...

ATTN...RFC...LMRFC...WGRFC...

LAT...LON   31898949 30898928 29929003 29419112 29559239 29669360
            29549439 29859473 30179469 31199398 31419281 31759172
            32349060 31898949