MESOSCALE PRECIPITATION DISCUSSION 0040
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
942 PM EDT MON APR 13 2015
 
AREAS AFFECTED......EASTERN AR/WESTERN TN/NORTHERN MS... 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 140141Z - 140641Z
 
SUMMARY...FLASH FLOODING WILL BECOME INCREASING LIKELY ACROSS
PORTIONS OF THE SCALLOPED AREA THROUGH THE EARLY OVERNIGHT HOURS
IN VICINITY OF SURFACE CONVERGENCE ZONES REINFORCED BY THE
CYCLONIC FLOW ACCOMPANYING THE MCV.

DISCUSSION...LOCAL WSR-88D IMAGERY SHOWS THUNDERSTORMS CONTAINING
EXTREMELY HEAVY RAINFALL FORMING WITHIN NARROW CONVERGENCE ZONES
DRAPED WEST OF MEMPHIS...SOUTH OF MEMPHIS...AND ALSO IN THE BROAD
CYCLONIC FLOW BETWEEN THEM.  ALTHOUGH CONVECTIVE INSTABILITY IS
GENERALLY WEAK...THE 00Z SHV RAOB SHOWS STEEPER LOWER LEVEL LAPSE
RATES ENTERING THE REGION FROM THE SOUTHWEST...WHICH IS THE SOURCE
REGION FOR SUFFICIENT INSTABILITY.

WITH THE MCV OVER SOUTHERN ARKANSAS ALSO APPROACHING THE
REGION...BROADER SCALE ENHANCEMENT OF THE CONVECTIVE UPDRAFTS IS
LIKELY TO CONTRIBUTE TO HIGHER RATES AND MORE WIDESPREAD
DEVELOPMENT.  ADDITIONALLY...AVERAGE CELL MOTIONS NEAR 10 KNOTS
AND VEERING WIND PROFILES ARE SUPPORTING LONGER DURATION RAINS AND
TRAINING ECHOES.

WHILE AREAS OF THE HEAVIEST RAINFALL ARE LIKELY TO BE SMALL AND
LOCALIZED...THE OVERALL CONDITIONS SUPPORT RAIN RATES APPROACHING
2 INCHES PER HOUR...WITH THE POTENTIAL TO LAST FOR 2 TO 3 HOURS. 
THESE RATES ALONG WITH THE DURATION WOULD EASILY EXCEED THE 3
HOURLY FFG VALUES...RESULTING IN FLASH FLOODING. 

JAMES

ATTN...WFO...HUN...JAN...LZK...MEG...OHX...

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

LAT...LON   36248916 36048788 34998779 34098878 33648993 
            34129068 34209163 34469200 35069159 35769036