MESOSCALE PRECIPITATION DISCUSSION 0123
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
323 PM EDT THU MAY 03 2018

AREAS AFFECTED...CENTRAL/NORTHERN AR...SOUTHERN MO...SOUTHERN
IL...FAR WESTERN KY...FAR WESTERN TN

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

VALID 031920Z - 040000Z

SUMMARY...ADDITIONAL ROUNDS OF SHOWERS AND THUNDERSTORMS WILL
MAINTAIN THE THREAT FOR SOME RUNOFF PROBLEMS AND POSSIBLE FLASH
FLOODING FOR SEVERAL MORE HOURS.

DISCUSSION...AN EXPANSIVE AXIS OF SHOWERS AND THUNDERSTORMS
CONTINUES TO IMPACT AN AREA FROM NORTHEAST TX UP ACROSS WESTERN
AND NORTHERN AR AND ACROSS SOUTHERN MO. THE CONVECTION CONTINUES
TO BE FAVORED BY A RELATIVELY DIFFLUENT FLOW REGION ALOFT TO THE
EAST OF THE CENTRAL/SOUTHERN PLAINS TROUGH AXIS...AND INTERACTION
WITH A MODESTLY UNSTABLE AIRMASS POOLED UP ACROSS THE LOWER MS
VALLEY WHERE MLCAPE VALUES OF 500 TO 1000 J/KG ARE NOTED.
MEANWHILE...PWATS ACROSS THE REGION ARE RATHER HIGH AT BETWEEN 1.6
TO 1.8 INCHES.

THE CONCERN OVER THE NEXT FEW HOURS WILL BE ADDITIONAL RAINS
OCCURRING OVER AREAS THAT SAW SOME HEAVY RAIN EARLIER TODAY AND
LAST NIGHT. THE MAIN CONCERN FOR RUNOFF AND FLASH FLOODING OVER
THE NEXT FEW HOURS SHOULD TEND TO BE UP ACROSS NORTHERN AR AND
SOUTHERN MO WITH SOME POTENTIAL ALSO FOR FAR SOUTHERN IL. THESE
AREAS HAVE SEEN MULTIPLE ROUNDS OF CONVECTION THIS MORNING WHICH
HAVE RESULT IN WET ANTECEDENT CONDITIONS. ADDITIONAL UPSTREAM
CONVECTION ENTERING WESTERN AR WILL TEND TO GAIN SOME
LATITUDE...AND THERE MAY BE SOME CONVECTIVE REDEVELOPMENT ALSO
NORTH OF AN OUTFLOW BOUNDARY THAT EXTENDS DOWNWIND FROM THE BROKEN
SQUALL-LINE OVER WESTERN AR TOWARD THE LOWER OH VALLEY.

THE OVERALL CONVECTIVE ENVIRONMENT SHOULD TEND TO BECOME LESS
FAVORABLE TOWARD EVENING AS RELATIVELY LIMITED INSTABILITY COUPLED
WITH THE LIFTING OUT OF STRONGER LARGE SCALE FORCING OVER THE
PLAINS SHOULD ALLOW CONVECTION TO BECOME MORE DISORGANIZED.
HOWEVER...AT LEAST FOR THE NEXT FEW HOURS...SUFFICIENT CONVECTION
WILL PERSIST TO AT LEAST MAINTAIN A SHORT-TERM THREAT FOR RUNOFF
PROBLEMS AND POSSIBLE FLASH FLOODING.

EXPECT LOCALLY AN ADDITIONAL 2 TO 3 INCHES OF RAIN TO BE
POSSIBLE...WITH THE HEAVIEST AMOUNTS GENERALLY ALIGNED ACROSS
PARTS OF FAR NORTHERN AR AND SOUTHERN MO WITH SOME EXTENSION INTO
SOUTHERN IL GOING THROUGH 00Z. THIS IS CONSISTENT WITH THE LATEST
HRRR/HRRR-EXP GUIDANCE.

ORRISON

ATTN...WFO...LSX...LZK...MEG...PAH...SGF...TSA...

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

LAT...LON   38608896 38458784 37468790 36548850 35728946
            35099066 34719165 34429276 34439386 35099419
            35889382 36509326 37429166 38039043