MESOSCALE PRECIPITATION DISCUSSION 0433
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
900 PM EDT SUN JUL 02 2017

AREAS AFFECTED...FAR NORTHERN TX...SOUTHERN/EASTERN OK...WESTERN
AR...EXTREME SOUTHWEST MO

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

VALID 030100Z - 030700Z

SUMMARY...LOCALLY VERY HEAVY RAINFALL IS EXPECTED OVERNIGHT. FLASH
FLOODING IS LIKELY...WHICH MAY BE SIGNIFICANT.

DISCUSSION...A LONG-LIVED MCV WHICH HAS BEEN SLOWLY ADVANCING EAST
ACROSS CENTRAL OK THROUGH THE AFTERNOON AND EARLY EVENING HOURS
HAS BECOME CONVECTIVELY QUITE ACTIVE OVER THE LAST SEVERAL HOURS
WITH MULTIPLE CLUSTERS OF THUNDERSTORMS ADVANCING EAST ACROSS
EASTERN OK AND NOW PUSHING INTO PARTS OF NORTHWEST AR AND EXTREME
SOUTHEAST MO WHERE THE LEADING EDGE OF THE CONVECTION CONTINUES TO
INTERACT WITH A MODERATE TO STRONGLY UNSTABLE AIRMASS AHEAD OF IT.
MLCAPE VALUES ACROSS CENTRAL/NORTHWEST AR AND INTO EXTREME
SOUTHWEST MO ARE LOCALLY OVER 2000 J/KG ALONG WITH ABOUT 30 KTS OF
EFFECTIVE BULK SHEAR HELPING TO SUSTAIN SOME ORGANIZED CELL
DEVELOPMENT.

MEANWHILE...AROUND THE SOUTHERN FLANK OF THE MCV ACROSS SOUTHERN
OK...THE SITUATION HERE IS BECOMING MORE ALARMING AS CONVECTION
ACROSS THIS AREA IS BECOMING MORE FOCUSED/ORGANIZED WITHIN AN AREA
OF ENHANCING LOW TO MID LEVEL CONVERGENCE. THIS IS EVIDENCED IN
THE LATE-DAY EXPERIMENTAL GOES-16 0.64 MICRON/VIS IMAGERY WHICH
SHOWS A DUAL FETCH OF AGITATED CU/TCU CONVERGING ON THE RED RIVER
AND ADJACENT AREAS OF SOUTHERN OK FROM STEPHENS AND CARTER
COUNTIES EAST-NORTHEAST TO PONTOTOC AND COAL COUNTIES. IN
FACT...CONVECTION IN THESE AREAS HAS BECOME QUITE INTENSE WITH A
STRONG OVERSHOOTING TOP NOTED OVER COAL COUNTY IN PARTICULAR OVER
THE LAST HOUR.

THE HRRR/HRRRX GUIDANCE IS IN VERY STRONG AGREEMENT IN SUGGESTING
A STRENGTHENING OF THE MCV OVERNIGHT...WITH A TIGHTENING OF THE
VORTICITY FIELDS AS IT MOVES TOWARD EASTERN OK AFTER 06Z. THIS
WILL RESULT IN NOTABLY STRONGER WIND FIELDS IN THE 925/700 MB
LAYER TOWARD AND ESPECIALLY AFTER 06Z ACROSS AREAS OF FAR NORTHERN
TX...THE GREATER RED RIVER VALLEY AND INTO SOUTHEAST OK AND
GRADUALLY PARTS OF WESTERN AR THROUGH 09Z. THIS WILL ENHANCE THE
MOISTURE/INSTABILITY TRANSPORT ACROSS THESE AREAS ALONG WITH A
SIGNIFICANTLY CONFLUENT LOW TO MID LEVEL SPEED CORE REACHING
BETWEEN 30 TO 50 KTS THAT WILL ENHANCE FORCING FOR SUSTAINABLE
BACKBUILDING AND TRAINING CONVECTION AROUND THE SOUTHERN FLANK OF
THE MCV.

THE THREAT OF VERY HEAVY RAINFALL IS HIGH ACROSS AREAS OF
ESPECIALLY SOUTHEAST OK TONIGHT WHERE REPEATED HRRR/HRRRX QPF
OUTPUT HAS BEEN SIGNALING TOTALS OF 4 TO 6+ INCHES OF RAIN THROUGH
06Z ALONE...AND ADDITIONAL HEAVY RAINS AFTER THIS PERIOD GOING
THROUGH 12Z WITH A NOTABLE SET-UP FOR A HIGH-IMPACT STORM EVENT.
LESSER AMOUNTS OF AS MUCH AS 2 TO 4+ INCHES ARE EXPECTED AT LEAST
LOCALLY ELSEWHERE ACROSS AREAS OF EASTERN OK...WESTERN AR AND INTO
FAR SOUTHWEST MO.

FLASH FLOODING IS LIKELY TONIGHT...WITH THE HIGH THREAT AREA AGAIN
FOCUSED OVER AREAS NEAR THE RED RIVER AND ESPECIALLY OVER
SOUTHEAST OK. SOME OF THIS MAY BE QUITE SIGNIFICANT AND SHOULD BE
MONITORED CLOSELY.

ORRISON

ATTN...WFO...FWD...LZK...OUN...SGF...SHV...TSA...

ATTN...RFC...ABRFC...LMRFC...MBRFC...WGRFC...

LAT...LON   37099473 37079353 36409257 35599249 34549315
            33819419 33499546 33489691 33769777 34219795
            34809748 35259668 35599624 36619568