MESOSCALE PRECIPITATION DISCUSSION 0349
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
157 PM EDT FRI JUN 22 2018

AREAS AFFECTED...SRN AR...NRN LA...NE TX...WRN MS

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

VALID 221756Z - 222156Z

SUMMARY...THUNDERSTORMS IN A MOISTURE-RICH ENVIRONMENT WILL
PRODUCE HEAVY RAINFALL THIS AFTERNOON. FLASH FLOODING IS
POSSIBLE...BUT ESPECIALLY IN SOUTHERN ARKANSAS WHERE 2 TO 5 INCHES
OF RAIN FELL THIS MORNING.

DISCUSSION...AN UPPER LEVEL JET STREAK WAS BRUSHING ACROSS THIS
REGION...AND WHEN COUPLED WITH VEERED LOW LEVEL FLOW / WARM
ADVECTION DOWNSTREAM OF THE CAPPED ENVIRONMENT IN TEXAS...THIS HAD
LED TO A CLUSTER OF SLOW MOVING STORMS WITH HEAVY RAINFALL IN AND
SURROUNDING BRADLEY COUNTY ARKANSAS. DUAL POL RADAR ESTIMATES FROM
KLZK INDICATED SIZABLE AREAS OF 2 TO 5 INCHES OF RAINFALL SINCE
EARLY MORNING...AND THERE WERE REPORTS OF FLASH FLOODING.

APPROACHING 18Z...MESOANALYSIS INDICATED CONFLUENT LOW LEVEL FLOW
WITH PRECIPITABLE WATER VALUES CLOSE TO 2.00 INCHES...MIXED LAYER
CAPE OF AT LEAST 1500 J/KG...AN UPSTREAM SHORTWAVE TROUGH THAT HAD
BEEN TIED TO OTHER THUNDERSTORM ACTIVITY IN OKLAHOMA...AND A
HEALTHY CUMULUS FIELD OVER SOUTHWEST ARKANSAS PER VISIBLE
SATELLITE IMAGERY. THUS...RENEWED THUNDERSTORM DEVELOPMENT SEEMS
LIKELY THIS AFTERNOON...DESPITE MARGINAL MID LEVEL LAPSE RATES.

WITH THE TRANSITION TO THE DEEPLY MIXED DAYTIME BOUNDARY
LAYER...ADDITIONAL THUNDERSTORMS WILL BE MORE PROGRESSIVE...AND
THIS IS INDICATED IN THE 12Z WRF-ARW...WRF-NMM...AND RECENT HRRR
RUNS. CELL MOTIONS...HOWEVER...WILL LIKELY CARRY SOME ADDITIONAL
RAINFALL INTO THE BRADLEY COUNTY AREA WHERE THERE WILL BE A HIGH
PERCENTAGE OF RUNOFF GIVEN SATURATED CONDITIONS. ELSEWHERE RAIN
RATES OF GREATER THAN 2 INCHES PER HOUR / GIVEN THE TROPICAL PW
ENVIRONMENT / MAY LEAD TO FLASH FLOODING...ESPECIALLY URBAN AND
POORLY DRAINED LOCATIONS. THE HIGH RESOLUTION MODELS GENERALLY
INDICATE ISOLATED 3 INCH RAIN AMOUNTS THIS AFTERNOON...WEIGHTED
MORE TOWARD NORTHEAST LOUISIANA AND WESTERN MISSISSIPPI WHERE
REPEATED ACTIVITY IS POSSIBLE JUDGING BY 18Z RADAR TRENDS AND
SIMULATED REFLECTIVITY FROM THE MODELS MENTIONED ABOVE.

BURKE

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

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

LAT...LON   34039274 33149062 32168986 31869095 32219248
            32359463 33119482