MESOSCALE PRECIPITATION DISCUSSION 0693
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
410 AM EDT TUE AUG 15 2017

AREAS AFFECTED...EAST-CENTRAL OK...CENTRAL/NORTHERN AR

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

VALID 150805Z - 151300Z

SUMMARY...HEAVY SHOWERS AND THUNDERSTORMS MAY TEND TO INCREASE A
BIT MORE IN COVERAGE AND ORGANIZATION OVER THE NEXT FEW HOURS. THE
RATHER SLOW CELL MOTION WILL FOSTER SOME HEAVY RAINFALL
AMOUNTS...WITH SOME FLASH FLOODING POSSIBLE.

DISCUSSION...RADAR IMAGERY HAS BEEN SHOWING A GRADUAL INCREASE IN
SHOWER AND THUNDERSTORM ACTIVITY OVER PARTS OF EAST-CENTRAL OK AND
EVEN MORE SO OVER WEST-CENTRAL AND NORTHWEST AR. GOES IR SATELLITE
IMAGERY HAS OVERALL BEEN SHOWING SOME ADDITIONAL COOLING OF THE
CONVECTIVE TOPS WHICH IS SUGGESTIVE OF A STRONGER FORCING
ENVIRONMENT AND THIS SHOULD BE CORRELATING TO HEAVIER RAINFALL
RATES AS A RESULT.

THE CONVECTION IS GENERALLY FORMING WITHIN A BROAD WARM ADVECTION
PATTERN WITH SOUTHWEST LOW TO MID LEVEL FLOW OUT AHEAD OF A
SHORTWAVE TROUGH ADVANCING EAST FROM THE SOUTHERN PLAINS INTO THE
LOWER MS VALLEY. THE LOW LEVEL SOUTHWEST FLOW IS ON THE ORDER OF
20 TO 30 KTS WHICH IS RELATIVELY MODEST...BUT THERE IS SUFFICIENT
ISENTROPIC ASCENT AND LARGE SCALE DIVERGENCE OVER THE REGION FOR
THE CONVECTION TO DEVELOP AND EXPAND IN COVERAGE. PWATS ARE ON THE
ORDER OF 2 INCHES...AND THE CONVECTION HAS BEEN TENDING TO FOCUS
ALONG A MODEST INSTABILITY GRADIENT WITH AS MUCH AS 1000 TO 1500
J/KG OF MLCAPE NOTED OVER SOUTHWEST AR.

SOME ADDITIONAL CONVECTIVE ORGANIZATION IS EXPECTED OVER THE NEXT
COUPLE OF HOURS AS THE LOW LEVEL JET STRENGTHENS A TAD MORE WHICH
WILL ENHANCE THE WARM ADVECTION A BIT MORE ALONG WITH THE
TRANSPORT OF DEEPER MOISTURE AND INSTABILITY. SOME LOW LEVEL SPEED
CONVERGENCE IS ALSO NOTED IN THE AREA WIND PROFILER DATA...AND
THIS WILL ALSO FACILITATE SOME GREATER CONVECTIVE ORGANIZATION.

EXPECT RAINFALL TOTALS OF AS MUCH AS 2 TO 4 INCHES WITH SOME
ISOLATED CONCENTRATED TOTALS POSSIBLY EXCEEDING 5 INCHES POSSIBLE
WHERE CELLS TEND TO REPEAT OVER THE SAME AREA. LOCALLY THE
ANTECEDENT CONDITIONS ARE RATHER WET AND SOME FLASH FLOODING
CONCERNS WILL EXIST AS A RESULT.

ORRISON

ATTN...WFO...LZK...MEG...TSA...

ATTN...RFC...ABRFC...LMRFC...

LAT...LON   36439112 35869033 35099055 34639184 34379340
            34459433 35099483 35829420 36379274