MESOSCALE DISCUSSION 1637
   NWS STORM PREDICTION CENTER NORMAN OK
   0321 AM CDT TUE JUL 21 2009
   
   AREAS AFFECTED...OK...TX
   
   CONCERNING...SEVERE THUNDERSTORM WATCH 610...611...
   
   VALID 210821Z - 211015Z
   
   THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH
   610...611...CONTINUES.
   
   LARGE AND LONG-LIVED CONVECTIVE COMPLEX CONTINUES TO SPREAD SWD/SEWD
   ACROSS OK EARLY TODAY. DAMAGING WIND GUSTS WILL CONTINUE TO BE THE
   PRIMARY THREAT FROM THE MORE INTENSE STORMS EMBEDDED WITHIN THE
   LARGER SCALE COMPLEX OVER THE NEXT 1-2 HOURS.
   
   CONVECTIVELY ENHANCED CYCLONIC CIRCULATION MAINTAINING OVERALL MCS
   STRUCTURE WAS QUITE EVIDENT ON THE OK/KS BORDER IN LATEST MOSAIC
   RADAR IMAGERY LOOP. AN INVERTED TROUGH/WIND SHIFT WAS TRAILING FROM
   THE LOW AND AIDING STORMS IN AN ARC ACROSS SWRN OK WWD TO THE TX
   PNHDL. WHILE THIS LINE OF CONVECTION HAS BEEN SPREADING SWD AT ABOUT
   30KT AND SHOWING SOME DECREASE IN LIGHTNING FLASH RATES...A NUMBER
   OF LOCATIONS HAVE RECENTLY OBSERVED SEVERE WIND GUSTS OVER 60KT WITH
   THE PASSAGE OF THE LINE. THUS...IT IS LIKELY THAT SEVERE WIND
   POTENTIAL WILL CROSS THE RED RIVER AND INTO PARTS OF NWRN
   TX...COVERED BY WW 611...WITHIN THE HOUR.
   
   FARTHER NORTH...NEW CONVECTION HAS APPEARED IN THE WAKE OF THE
   LINEAR SEGMENT IN SWRN OK...EAST OF A LINE FROM HBR TO CSM. IT IS
   POSSIBLE THAT A WEAK AND VERY SMALL-SCALE WAKE-LOW MAY BE
   CONTRIBUTING TO THIS DEVELOPMENT. IN ADDITION...BACKBUILDING
   CONVECTION HAS BEEN NOTED ON THE WRN EDGE OF THE MCS CIRCULATION
   OVER LOGAN COUNTY OK. THIS NEW DEVELOPMENT COULD ALSO POSE A THREAT
   OF DAMAGING WINDS IN PARTS OF WW 610 PRIOR TO EXPIRATION.
   
   ..CARBIN.. 07/21/2009
   
   
   ATTN...WFO...TSA...FWD...OUN...SJT...
   
   LAT...LON   33839794 33389792 33379994 35419999 35459946 36159940
               36179888 36449851 36429820 36119817 36129750 36029736
               35879720 35939670 35349667 35289646 35249601 34779604
               34749634 34779688 34549690 33809693 33839794