MESOSCALE PRECIPITATION DISCUSSION 0171
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
517 AM EDT SUN APR 30 2017

AREAS AFFECTED...AR...SOUTHERN MO...SOUTHERN IL...SOUTHWEST
IN...WESTERN KY...WESTERN TN

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

VALID 300915Z - 301515Z

SUMMARY...FLASH FLOODING WILL REMAIN LIKELY THROUGH MUCH OF THE
MORNING AS ADDITIONAL HEAVY SHOWERS AND THUNDERSTORMS CROSS THE
REGION WITH LOCALLY INTENSE RAINFALL RATES.

DISCUSSION...WIDESPREAD SHOWERS AND THUNDERSTORM ACTIVITY
CONTINUES THIS MORNING ACROSS MUCH OF AR...SOUTHERN MO AND
SOUTHERN IL ONCE AGAIN. THE CONVECTION CONTINUES TO BE FOSTERED BY
A STRONG WARM ADVECTION PATTERN OVER THE LOWER/MID MS VALLEYS
AHEAD OF A DEEP UPPER TROUGH/CLOSED LOW SYSTEM OVER THE SOUTHERN
HIGH PLAINS. AHEAD OF A DEEPENING SURFACE LOW PRESSURE CENTER IS A
TRANSPORT OF VERY MOIST AIR...WITH A NOSE OF 1.75 TO 2 INCH PWATS.
A STRONG LOW LEVEL JET OF 50 TO 60 KTS HAS BEEN FACILITATING THIS
AND ALSO THE ADVANCEMENT OF A MODERATE TO STRONGLY UNSTABLE
AIRMASS HIGHLIGHTED BY MUCAPE VALUES OF AROUND 2000 J/KG ACROSS
THE LOWER AND MID MS VALLEY.

OVER THE LAST COUPLE OF HOURS...THE STRONGEST CONVECTION HAS
GENERALLY BEEN ACROSS AREAS OF CENTRAL AND EASTERN AR WHERE THE
INSTABILITY HAS BEEN MUCH MORE PRONOUNCED IN THE BOUNDARY LAYER.
MEANWHILE...A QUASI-LINEAR CONVECTIVE BOW HAS BEEN ADVANCING
QUICKLY EAST-NORTHEAST ACROSS SOUTHEAST MO...SOUTHERN IL AND FAR
WESTERN TN...ALTHOUGH THIS HAS BEEN SHOWING SIGNS OF WEAKENING AS
IT ADVANCES DOWNSTREAM AWAY FROM THE NOSE OF GREATER INSTABILITY.
THE PRECIPITATION SHIELD ACROSS SOUTHERN MO THOUGH HAS BEEN
CHARACTERIZED BY PERSISTENT MODERATE TO HEAVY STRATIFORM RAIN WITH
SOME EMBEDDED ELEVATED CONVECTIVE ELEMENTS PRODUCING LOCALLY
HEAVIER RAINFALL RATES.

THE NEXT SEVERAL HOURS SHOULD BE CHARACTERIZED BY STRONG
THUNDERSTORM ACTIVITY OVER ESPECIALLY EASTERN AR AND GRADUALLY
NOSING INTO WESTERN KY/WESTERN TN AND NORTHWEST MS AS A COLD FRONT
APPROACHES FROM THE WEST AND IT INTERACTS WITH THE VERY
MOIST/UNSTABLE AIRMASS PRECEDING IT. RATHER STRONGLY DIFFLUENT
FLOW ALOFT WILL CONTINUE TO ENHANCE THE CONVECTIVE POTENTIAL.
EXPECT ADDITIONAL RAINFALL AMOUNTS OF 2 TO 4 INCHES ACROSS THESE
AREAS WITH ISOLATED HEAVIER AMOUNTS TO OVER 5 INCHES. FARTHER
NORTH OVER SOUTHERN MO AND INTO SOUTHERN IL/SOUTHWEST
IN...ADDITIONAL RAINFALL AMOUNTS OF 1 TO 2 INCHES WILL BE POSSIBLE
WHERE THERE WILL BE MORE STRATIFORM TYPE RAINFALL AND A FEW
CONVECTIVE ELEMENTS. GIVEN THE SATURATE SOIL CONDITIONS OVER MUCH
OF THE THREAT AREA...ENHANCED RUNOFF AND FLASH FLOODING WILL
CONTINUE.

ORRISON

ATTN...WFO...ILX...IND...JAN...LMK...LSX...LZK...MEG...OHX...
PAH...SGF...SHV...

ATTN...RFC...ABRFC...LMRFC...MBRFC...NCRFC...OHRFC...

LAT...LON   38808926 38748775 37898686 36828704 36088767
            35198873 34308947 33728982 32579081 32519185
            32769238 33219266 34489262 35699304 36889320
            37549264 38059144 38469049