MESOSCALE PRECIPITATION DISCUSSION 0688...CORRECTED
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
951 AM EDT MON AUG 14 2017

CORRECTED FOR TYPOS

AREAS AFFECTED...SOUTHERN AR, NORTHERN MS & NORTHERN AL

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

VALID 141351Z - 141951Z

SUMMARY...A CONVECTIVE COMPLEX IS SHOWING TRAINING CHARACTER
ACROSS SOUTHEAST AR AND NORTHERN MS.  HOURLY RAIN TOTALS UP TO
2.5" WITH LOCAL AMOUNTS TO 4" ARE EXPECTED.

DISCUSSION...THUNDERSTORMS ARE TRAINING BETWEEN THE TAIL END OF A
MID-LEVEL SHORTWAVE MOVING INTO WESTERN TN AND AHEAD OF AN MCV
MOVING ACROSS OK, NEAR AND AHEAD OF A WEAK SURFACE WAVE. 
PRECIPITABLE WATER VALUES OF 2.1-2.3" ARE SEEN IN THE REGION PER
GPS VALUES.  INFLOW AT 850 HPA IS CONVERGENT OUT OF THE
WEST-SOUTHWEST AT 15-20 KTS PER VAD WIND PROFILES, NEAR THE
MAGNITUDE OF THE 850-400 HPA WIND.  EFFECTIVE BULK SHEAR OF 25 KTS
IN THIS REGION COMBINED WITH NEARLY UNIDIRECTIONAL FLOW WITH
HEIGHT HAS LED TO THE TRAINING BAND.

THE MESOSCALE GUIDANCE HAS BEEN TOO SCATTERED WITH CONVECTION IN
THIS WARM AIR ADVECTION BAND, WHICH IS A TYPICAL BIAS.  THE 06Z
NAM CONEST, ADJUSTED SOUTH, LOOKS BEST, WHICH INDICATES THE
POTENTIAL FOR LOCAL AMOUNTS IN THE 3-4" RANGE THROUGH 20Z. 
BELIEVE THE FRONT/THERMAL BOUNDARY WILL JUMP NORTH TO THE SOUTHERN
EDGE OF THE CLOUD SHIELD IN THE NEXT 2-3 HOURS.  DAYTIME HEATING
SHOULD ERODE THE REST OF THE REMAINING CIN SHORTLY AND BUILD
MLCAPES 1000-1500 J/KG ACROSS CENTRAL MS/CENTRAL AL WHICH IS
GENERALLY INDICATED BY THE RAP GUIDANCE.  INFLOW AT 850 HPA SHOULD
REMAIN RELATIVELY CONSTANT, AND THERE IS THE RISK OF AN ADDITIONAL
PULSE OF CONVECTION IN THE SOUTHWEST PORTION OF THE MPD REGION
EARLY TO MID AFTERNOON, WHICH COULD EXACERBATE ISSUES.  HOURLY
RAIN TOTALS UP TO 2.5" WITH LOCAL AMOUNTS TO 4" ARE EXPECTED,
WHICH WOULD BE PROBLEMATIC IN AN AREA THAT HAS RECEIVED FOUR TIMES
THE AVERAGE PRECIPITATION NORMALLY EXPECTED DURING THE PAST WEEK
-- SOILS ARE AT LEAST PARTIALLY SATURATED.

ROTH

ATTN...WFO...BMX...HUN...JAN...LZK...MEG...MRX...OHX...SHV...

ATTN...RFC...LMRFC...SERFC...

LAT...LON   35148579 33888572 33039027 33169350 33969177
            34568949