MESOSCALE PRECIPITATION DISCUSSION 0647
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
305 PM EDT MON AUG 07 2017

AREAS AFFECTED...SOUTHEAST AR...NORTHEAST LA...CENTRAL/NORTHERN
MS...CENTRAL/NORTHERN AL

CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY

VALID 071900Z - 080100Z

SUMMARY...NUMEROUS CLUSTERS OF HEAVY SHOWERS AND THUNDERSTORMS
WILL CONTINUE INTO THE EVENING HOURS. FLASH FLOODING IS EXPECTED
TO BE LIKELY FOR SOME AREAS.

DISCUSSION...A WAVE OF LOW PRESSURE RIDING UP ALONG A WAVY AND
QUASI-STATIONARY FRONT WILL CONTINUE TO HELP FOCUS PLENTY OF DEEP
MOISTURE AND INSTABILITY ALONG AND SOUTH OF THE BOUNDARY. NUMEROUS
SHOWERS AND THUNDERSTORMS ARE IMPACTING SOUTHEAST AR/NORTHEAST LA
AND EAST ACROSS A LARGE AREA OF MS AND INTO WEST-CENTRAL AL. CLOUD
TOPS OVER THE LAST COUPLE OF HOURS HAVE BEEN COOLING A BIT FURTHER
WHICH IS SUGGESTIVE OF STRONG ASCENT/UPDRAFTS AND CORRESPONDINGLY
AN UPTICK IN RAINFALL RATES.

THE PWATS ARE GENERALLY BETWEEN 2.2 AND 2.4 INCHES AND COUPLED
WITH CIRA-LPW DATA SHOWING A HIGHLY CONCENTRATED LAYER OF MOISTURE
BETWEEN 500 MB AND 300 MB...A HIGHLY EFFICIENT ENVIRONMENT FOR
ENHANCED RAINFALL RATES IS IN PLACE. THESE MAY REACH AS HIGH AS 3
INCHES/HR IN THE STRONGER CONVECTIVE CORES AND ESPECIALLY OVER
AREAS WITH THE COLDEST CLOUD TOPS AT THIS TIME.

THE WAVE OF LOW PRESSURE WILL CONTINUE TO FOCUS ROBUST WARM
ADVECTION WITH ENHANCED MOISTURE/INSTABILITY TRANSPORT ALONG THE
FRONT THIS AFTERNOON AND INTO THE EVENING HOURS...AND THIS WILL BE
AIDED BY SOME WEAK RIGHT-ENTRANCE REGION JET DYNAMICS FROM AN
EXITING SHORTWAVE TO THE NORTH. SOME EPISODIC TRAINING OF
CONVECTIVE CELLS WILL BE EXPECTED AS THE ACTIVITY IS GENERALLY
ALIGNED WSW/ENE WITH THE MEAN LAYER FLOW.

THE RECENT HRRR GUIDANCE IS SUGGESTING AS MUCH AS 4 TO 6
ADDITIONAL INCHES OF RAIN THROUGH MID-EVENING...AND SOME ISOLATED
HEAVIER TOTALS ARE POSSIBLE. THESE TOTALS ARE LIKELY TO CAUSE SOME
FLASH FLOODING CONCERNS. WILL CONTINUE TO MONITOR.

ORRISON

ATTN...WFO...BMX...HUN...JAN...LZK...MEG...MOB...SHV...

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

LAT...LON   34558751 34468678 34138624 33548614 32868664
            32168827 31829010 31849141 32019233 32479316
            32859333 33299294 33739153 33859028 34348867