MESOSCALE PRECIPITATION DISCUSSION 0080
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
809 PM EDT WED MAR 28 2018

AREAS AFFECTED...NRN MS...NRN AL...SRN TN...CENTRAL TN

CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY

VALID 290008Z - 290438Z

SUMMARY...A FOCUSED HEAVY RAIN EVENT WAS CONGEALING OVER NORTHERN
MISSISSIPPI AND SOUTHERN TENNESSEE. THIS MAY EXPAND NORTH AND
EASTWARD. FLASH FLOOD GUIDANCE OF 2 INCHES IN 3 HOURS WILL LIKELY
BE EXCEEDED IN SOME LOCATIONS...AND ISOLATED FLASH FLOODING IS
LIKELY.

DISCUSSION...APPROACHING 00Z AN MCS HAD MATURED OVER NORTHERN
LOUSIANA INTO WESTERN MISSISSIPPI...WITH A BOWING SEGMENT HEADING
NORTHEAST. AHEAD OF THE BOW...CONVECTION WAS FORMING AND MERGING
RAPIDLY ALONG WHAT IS ESSENTIALLY A 700 MB FRONTAL ZONE TO THE
REAR OF A STRENGTHENING UPPER JET EXPECTED TO REACH 150 KNOTS OVER
THE MIDWEST STATES BY 06Z. THE EVENT WAS ALSO FOCUSED BY A WELL
TIMED 700-500 MB SHORTWAVE IN THE SOUTHERN STREAM JUST UPSTREAM OF
THE ONGOING MCS IN MISSISSIPPI.

THE SETUP...WITH 0-6 KM MEAN WIND NEARLY IDENTICAL TO CORFIDI
VECTORS FOR DOWNWIND PROPAGATION...WAS JUST ABOUT IDEAL FOR
TRAINING CELLS THROUGH 0430Z AHEAD OF THE BOW STRUCTURE...FROM
NORTHERN MS TO SOUTHERN AND CENTRAL TN. THE HRRR HAD LATCHED ONTO
THIS DEVELOPMENT...AND FOR SEVERAL RUNS HAD INDICATED A SWATH OF 2
TO 4 INCHES OF RAIN OCCURRING THROUGH LATE EVENING IN THIS AREA.
MEMPHIS...KNQA...88D RADAR WAS OUT OF SERVICE...BUT DATA FROM KGWX
AT LONGER RANGE HAD BEGUN TO INDICATE RAIN RATES ABOVE 1"/HR. THE
CELL MERGERS WILL LIKELY LEAD TO EVEN MORE EFFICIENT RATES. OTHER
BOUTS OF TRAINING CONVECTION MAY SET UP FARTHER EAST OVER
TIME...AND ALTHOUGH THIS REGION HAD BEEN RELATIVELY DRY IN RECENT
DAYS...IT APPEARS LIKELY THE 2"/3 HOUR FFG VALUES WILL BE EXCEEDED
IN SOME SPOTS...AND SHOULD LEAD TO AT LEAST ISOLATED FLASH
FLOODING.

BURKE

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

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

LAT...LON   36438681 36138609 35278653 33078905 33819055
            34928991 36178813