MESOSCALE DISCUSSION 1402
   NWS STORM PREDICTION CENTER NORMAN OK
   0233 PM CDT SUN JUN 26 2011
   
   AREAS AFFECTED...PORTIONS OF SRN TN...NRN MS...NRN AL...FAR ERN AR
   
   CONCERNING...SEVERE THUNDERSTORM WATCH 555...
   
   VALID 261933Z - 262100Z
   
   THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 555
   CONTINUES.
   
   AN ORGANIZED...LEADING-LINE/TRAILING-STRATIFORM MCS EXTENDING FROM
   PORTIONS OF MIDDLE TN INTO NRN AL AND FAR NERN MS HAS ASSUMED MORE
   OF A BOWING STRUCTURE PER RECENT AREA RADAR IMAGERY. WITH THIS
   FEATURE...THE SEVERE THREAT APPEARS TO BE EVOLVING DIFFERENTLY
   ACROSS TWO AREAS WITHIN WW555:
   
   1. FOR AREAS WEST OF INTERSTATE 65...SSEWD PROPAGATION OF THE LINE
   AND OVERALL CONVECTIVE VIGOR HAS BEEN MORE PRONOUNCED INVOF ITS
   INTERSECTION WITH A REMNANT OUTFLOW BOUNDARY FROM AN EARLIER MCS AND
   WITH WSW-ENE-ORIENTED HORIZONTAL CONVECTIVE ROLLS EMANATING FROM
   N-CNTRL MS. WITH 20-25 KT OF NNWLY EFFECTIVE BULK SHEAR...THIS
   ACTIVITY WILL LIKELY POSE AN ENHANCED THREAT FOR DMGG WIND GUSTS
   DURING THE NEXT FEW HOURS AS IT MOVES SEWD ACROSS PORTIONS OF NWRN
   AL AND FAR NERN MS WHERE A VERY UNSTABLE AIR MASS IS IN PLACE. WEST
   OF THE ONGOING CONVECTIVE LINE...THE SEVERE WEATHER THREAT CONTINUES
   AS A CUMULUS FIELD BUILDS NEAR A COMPOSITE OUTFLOW BOUNDARY
   /RESULTING FROM ONGOING AND EARLIER CONVECTION/...AND ADDITIONAL
   CONVECTION ACROSS SRN MO POTENTIALLY PROVIDES SOME IMPACT.
   HOWEVER...THIS THREAT WILL LIKELY AVOID FAR SWRN PORTIONS OF THE WW
   AREA IN PARTS OF NRN MS...WHERE COUNTIES HAVE BEEN CLEARED UPON
   COORDINATION WITH THE MEMPHIS WFO.
   
   2. FOR LOCATIONS ALONG AND EAST OF THE INTERSTATE 65 CORRIDOR... THE
   BOWING NATURE OF THE LINE IS RELATIVELY BETTER PRONOUNCED.
   HOWEVER...OUTFLOW SURGING AHEAD OF PARENT CONVECTION PER 0.5-DEGREE
   REFLECTIVITY FROM THE HYTOP AL RADAR SUGGESTS THAT THIS ACTIVITY MAY
   BE AT LEAST SLIGHTLY ELEVATED THUS HINDERING THE THREAT FOR DMGG
   WIND GUSTS. HOWEVER...A WELL-DEFINED TRANSITION ZONE FOLLOWING THE
   CONVECTIVE LINE REFLECTS A POTENTIALLY STRONG REAR-INFLOW
   JET...WHICH COULD YIELD AN ENHANCED THREAT FOR LOCALLY STRONG SFC
   WINDS. ADDITIONAL CONVECTION COULD DEVELOP INVOF THE LEADING EDGE OF
   THE SEWD-MOVING COLD POOL AND REMNANT OUTFLOW BOUNDARY...AS STRONG
   HEATING AMIDST SFC DEWPOINTS FROM THE UPPER 60S TO THE LOWER 70S HAS
   ALLOWED MLCAPE VALUES TO REACH 2000 TO 3000 J/KG. HOWEVER...WITH VWP
   DATA SUGGESTING A RELAXATION OF THE MID-LEVEL FLOW WITH SWD
   DISPLACEMENT FROM THE ONGOING CONVECTIVE LINE...CONVECTION COULD
   BECOME INCREASINGLY DISORGANIZED WITH TIME. NEVERTHELESS...DCAPE
   VALUES OF 1000-1200 J/KG WILL YIELD A THREAT FOR DMGG WIND GUSTS
   WITH WET MICROBURSTS.
   
   ..COHEN.. 06/26/2011
   
   
   ATTN...WFO...OHX...BMX...HUN...MEG...
   
   LAT...LON   34139018 35039063 35718998 35748840 35478608 34018552
               33678611 33818771 33888870 34139018