MESOSCALE PRECIPITATION DISCUSSION 0467
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
322 AM EDT SUN AUG 23 2015
 
AREAS AFFECTED...NERN MISSISSIPPI INTO NRN ALABAMA AND EXTREME SRN
TENNESSEE 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 230721Z - 231215Z
 
SUMMARY...FLASH FLOODING WILL BE POSSIBLE AHEAD OF A LOW-MID-LEVEL
VORTICITY MAX...FROM NERN MISSISSIPPI INTO NRN ALABAMA INTO
EXTREME SRN TENNESSEE. HIGH MOISTURE AND POSSIBLE TRAINING MAY
CAUSE A FEW RUNOFF ISSUES GIVEN ANOMALOUS RAINFALL OVER THE PAST
SEVERAL DAYS.

DISCUSSION...REGIONAL RADAR IMAGERY AT 07Z SHOWED A CLUSTER OF
THUNDERSTORMS MOVING TOWARD THE NRN AL/MS BORDER FROM NRN
MISSISSIPPI WITH CLOUD TOP COOLING NOTED ON INFRARED SATELLITE
IMAGERY. A WELL DEFINED VORTICITY MAXIMUM WAS NOTED THROUGH WATER
VAPOR NEAR THE AR/TN/MS BORDER...MOVING EAST...WITH PRECIPITABLE
WATER VALUES RANGING BETWEEN 1.75 AND 2.00 INCHES ACCORDING TO THE
LATEST BLENDED TPW IMAGERY ACROSS MUCH OF THE DEEP SOUTH.
UNIDIRECTIONAL WLY WINDS WERE PRESENT ACROSS THE MPD THREAT AREA
WITH THE LATEST VWP WINDS AT 850 AND 700 MB BETWEEN 15 AND 20
KTS...TOWARD THE WEAK SIDE...BUT MATCHING CLOSELY TO OBSERVED CELL
MOTIONS. 

RAP FORECAST SOUNDINGS INDICATE INSTABILITY IS BETWEEN 500-1500
J/KG AS OF 07Z...BUT FORECAST TO WANE THROUGH THE REST OF THE
MORNING WHICH IS ONE LIMITING FACTOR TO SUPPORT HEAVY RAINFALL
RATES. WEAK LOW LEVEL WINDS ARE ALSO A LIMITING FACTOR...BUT GIVEN
THE HIGH MOISTURE CONTENT AND 7-DAY RAINFALL TOTALS BETWEEN 300
AND 600 PERCENT OF NORMAL ACROSS PORTIONS OF NRN ALABAMA...FLASH
FLOOD GUIDANCE IS ONLY 1-2 IN/HR IN A FEW LOCATIONS. THESE VALUES
ARE ALREADY PRESENT ACCORDING TO DUAL POL RADAR ESTIMATES FROM
KGWX. AS THE SCATTERED CONVECTION CONTINUES EAST THROUGH
12Z...FLASH FLOODING WILL BE POSSIBLE.

OTTO

ATTN...WFO...BMX...HUN...JAN...MEG...OHX...

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

LAT...LON   35338605 34448562 33698583 33268707 33368923 
            34778958 35228831