MESOSCALE PRECIPITATION DISCUSSION 0348
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
751 AM EDT FRI JUN 22 2018

AREAS AFFECTED......SOUTHERN ARKANSAS...NORTHERN LOUISIANA...FAR
NORTHEAST TEXAS...

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

VALID 221150Z - 221750Z

SUMMARY...SHOWERS AND THUNDERSTORMS WILL EXPAND AND BACKBUILD THIS
MORNING AHEAD OF A QUASI-STATIONARY SURFACE FRONT. HOURLY RAINFALL
RATES PEAKING BETWEEN 2-3 INCHES MAY RESULT IN FLASH FLOODING.

DISCUSSION...THE LATEST GOES-16 LONGWAVE IR IMAGERY SHOWS A
COMPACT AREA OF COOLING CLOUD TOPS ACROSS SOUTHERN ARKANSAS, ALONG
AND JUST SOUTH OF A STATIONARY FRONTAL BOUNDARY AND ON THE
SOUTHERN PERIPHERY OF THE MID-UPPER LEVEL LOW. THE UPPER LEVEL
CONFLUENCE SOUTH OF THIS UPPER LOW IS INDUCING A RIBBON OF
STRONGER UPPER LEVEL FLOW THROUGH CENTRAL ARKANSAS -- 70 TO 90+
KTS AT 250 MB PER THE LATEST VAD WIND PROFILES AND RAP/HRRR
ANALYSIS. THE ENHANCED UPPER LEVEL DIVERGENCE WITHIN THE RIGHT
ENTRANCE REGION OF THIS JET STREAK, AND ENSUING UPTICK IN THE
LOW-LEVEL MOISTURE FLUX CONVERGENCE ALONG THE FRONT, WILL FURTHER
THE CONVECTIVE GROWTH/ORGANIZATION, ESPECIALLY THROUGH 1500 UTC.

THE THERMODYNAMIC ENVIRONMENT WITHIN THE OUTLOOK AREA IS QUITE
FAVORABLE FOR HEAVY AND POTENTIALLY EXCESSIVE RAINFALL,
PARTICULARLY FOR THE TIME OF DAY, WITH MUCAPES BETWEEN 2000-3000
J/KG AND PWATS OF 1.75-2.0" PER THE LATEST SPC MESOANALYSIS. IN
ADDITION, AS THE WEST-SOUTHWEST 925-850 MB FLOW ALONG AND SOUTH OF
THE SURFACE BOUNDARY INCREASES TO 25-30 KTS, THE RESULTANT UPWIND
PROPAGATION WILL ALLOW THE CONVECTION TO BACKBUILD AND TRAIN.
HOURLY RAINFALL RATES OF 2-3" ARE LIKELY WITHIN THE STRONGEST
CORES, WITH EVENT TOTALS OF 4-7 INCHES POSSIBLE IN A FEW AREAS PER
THE LATEST HIGH-RES CAM GUIDANCE.

HURLEY

ATTN...WFO...JAN...LZK...SHV...

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

LAT...LON   34169385 33889236 33689163 33449128 33069120
            32639141 32289210 32419328 32879413 33639441
            34069426