MESOSCALE PRECIPITATION DISCUSSION 0706
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
633 PM EDT FRI AUG 18 2017

AREAS AFFECTED...NORTHWEST AR & SOUTHWEST MO

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

VALID 182232Z - 190232Z

SUMMARY...THUNDERSTORMS ARE EXPANDING IN COVERAGE NEAR THE
MO/AR/OK BORDER JUNCTION.  HOURLY RAIN AMOUNTS TO 2" WITH LOCAL
AMOUNTS TO 4" APPEAR POSSIBLE.

DISCUSSION...THUNDERSTORMS ARE ATTEMPTING TO GROW IN SCALE ACROSS
NORTHWEST AR AND SOUTHWEST MO TO THE NORTH OF WHAT APPEARS TO BE A
MESOSCALE WAVE IN THE TEMPERATURE AND MOISTURE FIELD.  INFLOW AT
850 HPA IS CONVERGENT OUT OF THE WEST-SOUTHWEST AT 15-20 KTS PER
VAD WIND PROFILES, WITH EFFECTIVE BULK SHEAR OF ~40 KTS PER SPC
MESOANALYSES.  ML CAPE VALUES OF 2000-3500 J/KG LIE IN THIS
REGION.  PRECIPITABLE WATER VALUES ARE LIKELY 1.5-1.75".

THUNDERSTORMS SHOULD ATTEMPT TO GROW IN SCALE AS OUTFLOW
BOUNDARIES FROM THE ACTIVITY SOUTH OF KANSAS CITY AND SOUTHWEST OF
SPRINGFIELD MERGE.  OF THE MESOSCALE GUIDANCE, THE 18Z NAM CONEST
AND 12Z WRF NSSL HAD THE BEST IDEA WITH LOCAL AMOUNTS IN THE 3-4"
RANGE, THOUGH THEY APPEAR TOO FAR TO THE NORTH.  EXPECT
THUNDERSTORMS TO EXPAND IN COVERAGE AND BACKBUILD FOR ANOTHER 1-2
HOURS DUE TO SLIGHTLY INCREASING 850 HPA WIND FLOW BEFORE SHOWING
SOME FORWARD PROPAGATING CHARACTER TO THE EAST AT 25-30 KTS.  THE
AVAILABLE MOISTURE AND INSTABILITY FAVOR HOURLY RAIN TOTALS TO 2".
 THIS COULD BE A PROBLEM IN THE OZARKS/WITHIN AREA HILLS.

ROTH

ATTN...WFO...LZK...SGF...TSA...

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

LAT...LON   37989454 37659284 36809182 35839250 35989459