MESOSCALE PRECIPITATION DISCUSSION 0157
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
510 AM EDT SAT APR 29 2017

AREAS AFFECTED...CENTRAL/EASTERN OK...FAR SOUTHEAST KS...FAR
NORTHWEST AR...SOUTHERN MO...FAR SOUTHWEST IL

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

VALID 290910Z - 291510Z

SUMMARY...HIGH-IMPACT AND LIFE-THREATENING FLASH FLOODING IS
EXPECTED THIS MORNING AS STRONG THUNDERSTORMS CONTINUE TO TRAIN
OVER THE SAME AREA.

DISCUSSION...A VERY ACTIVE MORNING WITH TRAINING THUNDERSTORMS
CONTINUES ACROSS AREAS OF CENTRAL/NORTHEAST OK...FAR NORTHWEST AR
AND ACROSS SOUTHERN MO. ALREADY VERY HEAVY RAINFALL HAS OCCURRED
AND ADDITIONAL HEAVY RAIN IS EXPECTED THIS MORNING AS A WIDESPREAD
AXIS OF THUNDERSTORMS CONTINUES TO SUSTAIN ITSELF.

THIS IS BEING FACILITATED BY A SLOW-MOVING UPPER TROUGH THAT IS
SLOWLY EJECTING EAST OUT INTO THE SOUTHERN HIGH PLAINS. MEANWHILE
DOWNSTREAM FROM THIS ACROSS THE LOWER MS VALLEY REGION...A STRONG
WARM ADVECTION PATTERN CONTINUES WITH A DEEP LAYER FETCH OF
MOISTURE AND INSTABILITY SURGING NORTHWARD INTO A STRONG FRONTAL
ZONE THAT IS ORIENTED FROM NORTH OF THE RED RIVER UP ACROSS
NORTHERN AR AND THEN EAST INTO THE OH VALLEY. IN FACT...AREA VWP
DATA IS INDICATING A S/SW LOW LEVEL JET OF AS MUCH AS 60 KTS
ACROSS NORTH TEXAS AND CENTRAL AR. PWATS OF 1.6 TO 1.8 INCHES ARE
NOTED OVER EASTERN OK AND INTO NORTHERN AR AND SOUTHERN MO...WITH
IMPRESSIVELY HIGH MUCAPE VALUES OF 3000 TO 4000 J/KG ALONG THE
FRONT.

THE THERMODYNAMICS ALONE ARE SUFFICIENT TO DRIVE INTENSE RAINFALL
RATES...BUT WITH A COUPLED JET STRUCTURE ADVANCING EAST OUT INTO
THE SOUTHERN HIGH PLAINS...THE UPPER LEVEL FLOW ACROSS
CENTRAL/EASTERN OK AND THROUGH SOUTHERN MO IS QUITE DIFFLUENT AND
IS HELPING TO PROVIDE ADDITIONAL DEEP LAYER ASCENT.

EXPECT RAINFALL RATES AGAIN TO BE UPWARDS OF 2 INCHES/HR...WITH
LOCALLY HEAVIER RATES WHERE OVERSHOOTING TOP ACTIVITY OCCURS. THE
LATEST HRRR GUIDANCE FAVORS AS MUCH AS 3 TO 5 INCHES OF ADDITIONAL
RAIN OVER PARTS OF NORTHEAST OK...FAR NORTHWEST AR AND SOUTHERN MO
THROUGH LATE MORNING. THE 00Z ARW/NSSL-WRF GUIDANCE ALSO INDICATES
HEAVY AMOUNTS WITH JUST SOMEWHAT LESSER AMOUNTS. IN ANY
CASE...THESE ADDITIONAL RAINS WILL BE FALLING OVER AREAS THAT HAVE
ALREADY SEEN LOCALLY AS MUCH AS 3 TO 5 INCHES OF RAIN. THE
SATURATED SOIL CONDITIONS WILL RESULT IN SIGNIFICANT RUNOFF
PROBLEMS THIS MORNING AND A LIKELIHOOD OF LIFE-THREATENING FLASH
FLOODING.

ORRISON

ATTN...WFO...ICT...LSX...LZK...OUN...PAH...SGF...TSA...

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

LAT...LON   38598989 38428913 37938889 37328951 36989070
            36439159 36109243 35919349 35659453 35329567
            35019710 35009787 35519817 36329760 37029670
            37459569 37769460 37919310 38169212 38469083