MESOSCALE PRECIPITATION DISCUSSION 0211
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
728 PM EDT THU MAY 11 2017

AREAS AFFECTED...NORTHEAST AR...BOOTHEEL OF MO...SOUTHWEST
KY...CENTRAL/WESTERN TN

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

VALID 112325Z - 120525Z

SUMMARY...SHOWERS AND THUNDERSTORMS WILL INCREASE IN COVERAGE OVER
THE NEXT SEVERAL HOURS. THE RELATIVELY SLOW CELL MOVEMENT COUPLED
WITH INTENSE RAINFALL RATES UP TO 2 INCHES/HR MAY RESULT IN SOME
FLASH FLOODING CONCERNS.

DISCUSSION...NUMEROUS SHOWERS AND THUNDERSTORMS OVER AREAS OF
NORTHERN AR AND SOUTHERN MO WILL GRADUALLY DEVELOP OFF TO
NORTHEAST AS WARM ADVECTION STRENGTHENS A BIT THIS EVENING AHEAD
OF THE LARGER SCALE UPPER TROUGH OVER THE SOUTHERN PLAINS. THERE
ARE POCKETS OF RATHER ROBUST INSTABILITY POOLED ALONG AND SOUTH OF
THE FRONTAL ZONE SLICING THROUGH THE OH RIVER VALLEY AND BACK
ACROSS SOUTHERN MO...WITH AS MUCH AS 1500 TO 2000 J/KG OF MLCAPE.
THIS INSTABILITY WILL BE INSTRUMENTAL IN ALLOWING CONVECTION TO
DEVELOP FARTHER EAST THIS EVENING AND ALSO WITH THE AID OF SOME
IMPROVING UPPER JET SUPPORT AS SUGGESTED BY THE LATEST RAP
GUIDANCE WHICH HAS A WEAK COUPLED JET STRUCTURE DEVELOPING OVER
CENTRAL/EASTERN AR BY LATE EVENING.

THE CELL MOTIONS SHOULD BE RATHER WEAK AND SO THIS WILL TEND TO
ENHANCE THE RAINFALL TOTALS WITH THE CONVECTION. RAINFALL RATES UP
TO 2 INCHES/HR ARE EXPECTED...WITH SOME STORM TOTALS OF 2 TO 4
INCHES EXPECTED THROUGH MIDNIGHT AS SUGGESTED BY A CONSENSUS OF
THE CAM GUIDANCE...AND ESPECIALLY THE RECENT HRRR/HRRRX RUNS.
ALTHOUGH IT IS NOTED THAT THE CAM GUIDANCE APPEARS TO BE A BIT TOO
SLOW IN ADVANCING CONVECTION EAST WITH TIME. IN ANY CASE...THESE
EXPECTED RAINFALL TOTALS WILL PROMOTE AT LEAST SOME FLASH FLOOD
CONCERNS.

ORRISON

ATTN...WFO...LMK...MEG...OHX...PAH...

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

LAT...LON   37348762 37198679 36628620 36178622 35488716
            35088876 34969033 35409086 36119066 36878963
            37218869