MESOSCALE DISCUSSION 1638
   NWS STORM PREDICTION CENTER NORMAN OK
   0802 PM CDT FRI AUG 03 2007
   
   AREAS AFFECTED...NRN NEB...SWRN...CENTRAL...ERN SD
   
   CONCERNING...TORNADO WATCH 561...
   
   VALID 040102Z - 040300Z
   
   THE SEVERE WEATHER THREAT FOR TORNADO WATCH 561 CONTINUES.
   
   LONE SUPERCELL OVER KEYA PAHA COUNTY IN NCENTRAL NEB WILL CONTINUE
   TO MOVE SLOWLY /AROUND 10 KTS/ ESEWD ALONG A STATIONARY BOUNDARY
   ACROSS FAR NRN NEB FOR THE NEXT COUPLE OF HRS AND REMAIN CAPABLE OF
   PRODUCING ISOLATED TORNADO. ADDITIONAL TSTMS OVER THE REMAINDER OF
   WW 561 HAVE SHOWN RECENT WEAKENING TRENDS...AN ISOLATED SVR TSTM OR
   TWO MAY MOVE INTO FAR WRN PORTION OF WW 591. SVR THREAT SHOULD
   TRANSITION INTO A HEAVY RAIN THREAT OVER THE NEXT FEW HOURS...ACROSS
   CENTRAL/SERN SD AND NERN NEB.
   
   LATEST SFC ANALYSIS SHOWS A PERSISTENT PRESSURE FALL CENTER OVER
   NCENTRAL NEB AHEAD OF LONE SUPERCELL OVER KEYA PAHA COUNTY. STRONG
   LOW LEVEL WAA PROFILE WILL SUSTAIN THIS SUPERCELL FOR THE NEXT FEW
   HOURS AND SUPPORT THE THREAT FOR ISOLATED TORNADOES. A LOCAL
   EXTENSION OF WW 591 MAY BE NECESSARY FOR HOLT COUNTY AHEAD OF THIS
   SUPERCELL. A WELL DEFINED OUTFLOW/SYNOPTIC BOUNDARY ORIENTED FROM
   SCENTRAL SD INTO NERN NEB...AND STRONG LOW LEVEL JET IMPINGING
   NEARLY PERPENDICULAR TO THIS BOUNDARY...ADDITIONAL CONVECTION IS
   EXPECTED TO CONTINUE TO DEVELOP ALONG THE COOL SIDE OF THE BOUNDARY
   OVER CENTRAL/ERN SD WITH HEAVY RAIN BECOMING THE PRIMARY THREAT
   ACROSS THIS AREA.
   
   ..CROSBIE.. 08/04/2007
   
   
   ATTN...WFO...FSD...OAX...ABR...GID...LBF...UNR...
   
   44539908 44829970 44530081 43830115 43380114 42900135
   42340183 41840127 41720060 41669974 41649913 41699844
   42069794 42529773 43089754 43449730 44049803 44339872