MESOSCALE PRECIPITATION DISCUSSION 0089
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
956 AM EDT SAT JUN 01 2013
 
AREAS AFFECTED......NORTHEAST ARKANSAS AND WESTERN TENNESSEE... 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 011355Z - 011955Z
 
SUMMARY...A NEARLY STEADY-STATE RAINFALL SYSTEM OVER ARKANSAS
FAVORS A HIGH PROBABILITY OF EXCEEDING FLASH FLOOD GUIDANCE ACROSS
PORTIONS OF NORTHEAST ARKANSAS AND WESTERN TENNESSEE THROUGH EARLY
OR MID AFTERNOON.

DISCUSSION...RADAR AND SATELLITE IMAGERY SHOW THE MID-LEVEL CENTER
OF A MESOSCALE RAINFALL SYSTEM NORTH OF LITTLE ROCK MOVING
EASTWARD...WHILE SURFACE ANALYSIS SHOWS A STALLED OUTFLOW BOUNDARY
ALONG A LINE FROM ABOUT LEXINGTON TO JUST SOUTH OF CLARKSVILLE TO
A MESO-LOW NEAR JONESBORO.  A PROGRESSIVE OUTFLOW BOUNDARY EXTENDS
SOUTHWESTWARD FROM THE MESO-LOW.  DEEP CONVECTION CONTINUES TO
DEVELOP NORTH OF MESOSCALE BOUNDARIES...WITH REGIONAL VAD WIND
PROFILER DATA...RAP ANALYSIS...AND LIGHTNING TRENDS INDICATING
THAT THE MAJORITY OF CONVECTION IS ROOTED IN THE 850 TO 700 MB
LAYER.

HI-RESOLUTION MODEL DATA CORRELATES ONLY MODESTLY WITH RADAR
DATA...WITH THE 12Z HRRR AND 00Z HI-RES ARW TOO FAR NORTH WITH THE
CONVECTION WHICH APPEARS TO BE A RESULT OF THE MODELS NOT
ADEQUATELY HANDLING THE MORE PROGRESSIVE OUTFLOW BOUNDARY
EXTENDING SOUTHWESTWARD FROM THE LOW.  THUS...THE SHORT RANGE
FORECAST IS BASED LARGELY ON MESO-ANALYSIS AND CONCEPTIONAL
MODELING.

THE MORE BROAD UPPER TROUGH OVER THE CENTRAL PLAINS SHOULD ALLOW
FOR LESS DIURNAL WEAKENING OF THE 850-700 MB FLOW AHEAD OF THE
TROUGH THAN WOULD NORMALLY BE EXPECTED...WHICH SHOULD HELP TO
SUSTAIN THE CURRENT CONVECTIVE ACTIVITY THROUGH AT LEAST EARLY
AFTERNOON...WITH REPEATED CELL DEVELOPMENT AND TRAINING EXPECTED. 
ADDITIONAL RAINFALL AMOUNTS THROUGH EARLY OR MID AFTERNOON OF 1 TO
2 INCHES ARE EASILY ATTAINABLE...WITH 2 TO 4 INCHES POSSIBLE
LOCALLY.  GIVEN THE ALREADY REDUCED FLASH FLOOD GUIDANCE
VALUES...THE PROBABILITY OF EXCEEDING GUIDANCE IS HIGH...
ESPECIALLY OVER WESTERN TENNESSEE.

JAMES


ATTN...WFO...OHX...PAH...MEG...LZK...

LAT...LON   35588779 34978915 34589050 34469205 34699250 35229226
            36239063 36368934 36348919 36278743 35588779