MESOSCALE DISCUSSION 2146
   NWS STORM PREDICTION CENTER NORMAN OK
   0633 PM CDT TUE SEP 06 2011
   
   AREAS AFFECTED...PORTIONS CENTRAL/ERN NC...SERN VA...ERN SC.
   
   CONCERNING...TORNADO WATCH 848...
   
   VALID 062333Z - 070130Z
   
   THE SEVERE WEATHER THREAT FOR TORNADO WATCH 848 CONTINUES.
   
   WW MAY CLEARED FROM W-E IN STEP WITH POSITION/SHIFT OF UNFAVORABLE
   BOUNDARY-LAYER AIR W AND NW OF BOUNDARIES DESCRIBED BELOW. 
   OTHERWISE...PRIND WW MAY BE ALLOWED TO EXPIRE AS SCHEDULED AT 01Z. 
   SVR THREAT...WHILE NOT ENTIRELY ABSENT...WILL DIMINISH SLOWLY WITH
   TIME THROUGH EVENING.
   
   23Z SFC MESOANALYSIS SHOWS PRIMARY SFC LOW INVOF TRI...OCCLUDED
   FRONT ESEWD TO TRIPLE POINT BETWEEN CLT-VUJ.  FROM THERE COLD FRONT
   WAS ANALYZED SWD BETWEEN SSC-FLOW AND APCHG CHS.  QUASISTATIONARY
   FRONT EXTENDED NEWD NEAR RDU...EMV...WAL.  WITH CONTINUED NELY FLOW
   TO ITS N AND REINFORCEMENT OF SFC-BASED STATIC STABILITY BY
   PRECIP...ONLY MINOR LOCALIZED DRIFTING IS EXPECTED WITH LATTER
   BOUNDARY DURING NEXT 2-3 HOURS...THOUGH SOME NWWD RETREAT IS
   POSSIBLE OVER SRN CHESAPEAKE BAY REGION LATER THIS EVENING AS PARENT
   CYCLONE MOVES SLOWLY NNEWD.  COLD FRONT...WHICH SO FAR HAS BEEN
   CHARACTERIZED MORE STRONGLY BY DRYING THAN SENSIBLE COOLING GIVEN
   DIABATIC HEATING OF POSTFRONTAL BOUNDARY LAYER...SHOULD CONTINUE TO
   MOVE EWD ACROSS ERN SC AND SRN/ERN NC...ENDING SVR THREAT FROM W-E.
   
   MEANWHILE...AIR MASS BETWEEN FRONTS WILL BE CHARACTERIZED BY RICH
   LOW-LEVEL MOISTURE/THETAE...WITH SFC DEW POINTS 70S F...HELPING TO
   OFFSET WEAK LAPSE RATES ALOFT IN MAINTAINING AT LEAST MRGL BUOYANCY.
    MLCAPE WILL DIMINISH GRADUALLY WITH ONSET OF NOCTURNAL SFC
   COOLING...BUT REMAIN SFC-BASED WITH MLCAPE VALUES 500-1500 J/KG
   THROUGH ABOUT 03Z.  STRONGEST DEEP-LAYER SHEAR NOW IS ALONG AND W OF
   COLD FRONT AND SHOULD REMAIN SO...THOUGH LOW-LEVEL SRH WILL REMAIN
   MAXIMIZED INVOF QUASISTATIONARY BOUNDARY FARTHER N AND NE.  CORRIDOR
   OF 150-250 J/KG EFFECTIVE SRH ALSO MAY PERSIST SWD ACROSS SERN NC. 
   ANY RELATIVELY SUSTAINED/DISCRETE CELLS INTERACTING WITH THAT
   BOUNDARY AND CROSSING NEAR SERN NC SRH AXIS STILL MAY POSE TORNADO
   RISK.  HOWEVER...AMBIENT WIND PROFILE WILL CONTINUE TO FEATURE
   BACKING WITH HEIGHT IN VARIOUS MID-UPPER TROPOSPHERIC
   LAYERS...SUPPORTING DOMINANCE OF SEGMENTED/QUASI-LINEAR MODES.
   
   ..EDWARDS.. 09/06/2011
   
   
   ATTN...WFO...AKQ...MHX...RAH...ILM...RNK...
   
   LAT...LON   33197926 33977988 35627922 36547882 37167672 36817603
               35547622 34477648 34667662 34607720 34277774 34027789
               33697796 33897805 33687883 33477906 33197926