MESOSCALE PRECIPITATION DISCUSSION 0059
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1243 PM EDT TUE MAY 21 2013
 
AREAS AFFECTED...ARKLATEX 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 211605Z - 212005Z
 
SUMMARY...A MORNING LINE OF HEAVY CONVECTIVE RAIN THAT EXTENDED
FROM SPS TO FSM HAS PUSHED TOWARD THE ARKLATEX OR A MUCH MORE
UNSTABLE ENVIRONMENT... WHILE AN IMPRESSIVE SHORT WAVE IMPULSE AND
ADDITIONAL SEVERE CONVECTION IS DEVELOPING JUST UPSTREAM. THE
COMBINATION AND INTERACTION OF THE TWO THIS AFTN COULD LEAD TO
MORE HEAVY CONVECTIVE RAINS AND POSSIBLE FLASH FLOODING.

DISCUSSION...A WELL-DEFINED OUTFLOW BOUNDARY/PRE-FRONTAL TROUGH
AHEAD OF THE STRONG SURFACE COLD FRONT HAS SURGED INTO A VERY
UNSTABLE AIR MASS NEAR THE ARKLATEX. THIS BOUNDARY SHOULD BE THE
FOCUS FOR THE ADDITIONAL UPSTREAM ACTIVE CONVECTION TO FOCUS ALONG
MIDDAY/EARLY THIS AFTN. FACTOR IN THE STRONG DIURNAL HEATING AND
ANOMALOUS MOISTURE CONTENT IN THIS REGION AND THE THREAT FOR FLASH
FLOODING WILL BE POSSIBLE. PWS REMAIN AOA 1.75 TO 2 INCHES...
WHICH IS STILL 1.5 TO 2 TIMES ABOVE AVG GFS AND ECMWF STANDARDIZED
ANOMALIES. THE FFG HERE IS ACTUALLY QUITE A BIT HIGHER...
GENERALLY 2 TO 2.5 INCHES WITHIN AN HR.  EXPECT 1 TO 3 INCH
AMOUNTS WITH LOCALLY HIGHER VALUES AND POSSIBLE FLASH FLOODING
BEFORE THE SYSTEM FINALLY BEGINS TO PROGRESS DOWNSTREAM THIS
EVENING.  

MUSHER


ATTN...WFO...LZK...SHV...TSA...FWD...OUN...

LAT...LON   34579167 34949218 34809359 34509515 34119702 33679803
            33129769 32799651 32859455 33489265 34079198 34579167