MESOSCALE PRECIPITATION DISCUSSION 0252
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1243 PM EDT FRI JUN 01 2018

AREAS AFFECTED...EAST CENTRAL AR...SOUTHWESTERN TN....NORTHERN
MS...NORTHERN AL

CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE

VALID 011642Z - 012100Z

SUMMARY...CONVECTIVE REGENERATION ACROSS THE SAME AREAS COULD LEAD
TO LOCALIZED RAINFALL AMOUNTS OF 2-5 INCHES THROUGH 21Z. FLASH
FLOODING IS POSSIBLE.

DISCUSSION...A COLD POOL ASSOCIATED WITH CONVECTION EARLIER THIS
MORNING HAS RESULTED IN A DIFFERENTIAL HEATING BOUNDARY/MESOSCALE
FRONT ACROSS THE OUTLINED AREA. SOUTHERLY FLOW AT THE SURFACE
TRANSPORTING HIGH DEWPOINT (72 DEG F+) AIR NORTHWARD ACROSS THE
BOUNDARY IS ALREADY RESULTING IN SOME RENEWED CONVECTIVE
GENERATION EAST OF MEMPHIS. A BROADER AREA OF LOW-LEVEL
CONVERGENCE, AS EVIDENCED IN 850 HPA FLOW, HAS POOLED MOISTURE
ACROSS THIS AREA WITH VERY HIGH PRECIPITABLE WATER VALUES (1.8-2.0
INCHES) EVIDENT IN LATEST SPC MESOANALYSIS. RAINFALL RATES OF
1-1.5 IN/HR ARE ESTIMATED BY RADAR IN THE CURRENT CONVECTION
ACROSS SOUTHWESTERN TN.

AS INSTABILITY INCREASES OVER THE NEXT COUPLE HOURS, PRECIPITATION
EFFICIENCY WILL INCREASE, AND COULD LEAD TO RAINFALL RATES NEAR 2
IN/HR IN THE STRONGEST CONVECTION. ADDITIONALLY, CELL
TRAINING/MERGERS ARE EXPECTED TO INCREASE HEAVY RAIN DURATION FOR
SOME AREAS DUE TO THE LINGERING SURFACE BOUNDARY. THE HRRR SEEMED
TO HAVE THE BEST HANDLE ON THE ONGOING CONVECTION AND SHOWS THAT
AS CONVECTION BECOMES MORE ORGANIZED BY MID TO LATE AFTERNOON,
STORMS SHOULD BEGIN TO PROPAGATE SOUTHWARD MORE MORE QUICKLY
ACROSS NORTHERN MS/AL. THE HRRR AND HRRR-EXPERIMENTAL BOTH SUGGEST
THAT LOCALIZED RAINFALL MAXIMA EXCEEDING 5 INCHES ARE POSSIBLE
THROUGH 21Z. THESE RAINFALL RATES/AMOUNTS COULD LEAD TO FLASH
FLOODING.

RYAN

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

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

LAT...LON   35778849 35468724 34878683 34428684 33958744
            33888816 33948904 34158977 34439049 34709100
            35059081 35269001 35478943