MESOSCALE DISCUSSION 1908
   NWS STORM PREDICTION CENTER NORMAN OK
   0834 PM CDT MON AUG 17 2009
   
   AREAS AFFECTED...TX PANHANDLE...WRN/NRN OK
   
   CONCERNING...SEVERE THUNDERSTORM WATCH 708...
   
   VALID 180134Z - 180230Z
   
   THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 708
   CONTINUES.
   
   MCS IS GRADUALLY EXPANDING IN AREAL COVERAGE OVER THE SRN PLAINS
   FROM THE ERN TX PANHANDLE...INTO WCNTRL OK.  IT APPEARS A
   SIGNIFICANT COLD POOL...SUFFICIENT ENOUGH TO ALTER FORWARD
   PROPAGATION COMPONENT...HAS DEVELOPED BENEATH THE EXPANDING
   PRECIPITATION AND IS DRIVING LEADING EDGE OF CONVECTION AT ROUGHLY
   30KT ACROSS CUSTER/BECKHAM COUNTIES IN OK.  00Z SOUNDING FROM OUN
   EXHIBITED A THERMODYNAMIC ENVIRONMENT FAVORABLE FOR STORM
   MAINTENANCE...THOUGH VERTICAL SHEAR IS SOMEWHAT MARGINAL.  GIVEN
   THAT THE LLJ WILL REMAIN ESTABLISHED ACROSS THE HIGH PLAINS OVER THE
   TX PANHANDLE...IT APPEARS STORM-SCALE PROCESSES...NAMELY
   OUTFLOW...WILL STEER MCS ACROSS WRN/NRN OK INTO PORTIONS OF CNTRL OK
   OVER THE NEXT FEW HOURS.  IF CONVECTION REMAINS STRONG/SEVERE...A
   LOCAL EXTENSION TO WW708 MAY BE NEEDED ACROSS THIS REGION.
   
   FARTHER WEST...LONG LIVED SUPERCELL CONTINUES DIGGING SEWD ACROSS
   THE NWRN TX PANHANDLE THROUGH DALLAM INTO SHERMAN COUNTY.  WITH LLJ
   EXPECTED TO INCREASE AHEAD OF THIS STORM ATOP COOLER RAIN-COOLED
   AIRMASS...IT WOULD SEEM ADDITIONAL ELEVATED THUNDERSTORMS COULD
   DEVELOP AHEAD OF THIS STRONG STORM.  AS ACROSS CNTRL OK...A LOCAL
   EXTENSION MAY BE REQUIRED FOR THE NERN HALF OF THE TX PANHANDLE.
   
   ..DARROW.. 08/18/2009
   
   
   ATTN...WFO...TSA...ICT...OUN...LUB...AMA...
   
   LAT...LON   36729655 35499756 34799916 34570057 35340144 36180265
               36590200 35540008 36049904 37029741 36729655