MESOSCALE DISCUSSION 1637
   NWS STORM PREDICTION CENTER NORMAN OK
   0549 PM CDT FRI AUG 03 2007
   
   AREAS AFFECTED...CENTRAL/WRN NEB...WRN/SCENTRAL SD
   
   CONCERNING...TORNADO WATCH 561...
   
   VALID 032249Z - 040045Z
   
   THE SEVERE WEATHER THREAT FOR TORNADO WATCH 561 CONTINUES.
   
   CLUSTER OF STG-SVR TSTMS WILL CONTINUE TO MOVE EWD AROUND 20 KTS
   ACROSS WW 561 OVER THE NEXT FEW HOURS. THREAT FOR ISOLATED TORNADOES
   WILL CONTINUE...MAINLY INVOF OF STATIONARY/OUTFLOW BOUNDARY LOCATED
   GENERALLY ALONG THE SD/NEB BORDER. THOUGH NOT CURRENTLY
   ANTICIPATED...AN ADDITIONAL WW MAY BE NEEDED EAST OF WW
   561...DEPENDING ON CONVECTIVE TRENDS IN THE COUPLE OF HOURS.
   
   LATEST SFC ANALYSIS SHOWS A STATIONARY BOUNDARY EXTENDING FROM NEAR
   RAP ESEWD TO ALONG THE SD/NEB BORDER AND THEN SEWD INTO SERN NEB. AN
   AXIS OF SFC PRESSURE FALLS EXTENDS SEWD FROM THE SFC LOW THROUGH
   WRN/CENTRAL NEB.  AN UPPER LEVEL WAVE WAS MOVING TOWARDS THE AREA
   FORM CENTRAL WY...AND LARGE SCALE LIFT WILL CONTINUE TO SUPPORT
   MODERATE WAA AND VERTICAL MOTION. RECENT PROFILER DATA FROM MRR
   CONFIRMS A STRENGTHENING LOW LEVEL JET OVER THE LAST FEW HOURS.
   RELATIVELY STRONG LOW LEVEL SHEAR EXISTS OVER THE REGION AS A RESULT
   /0-1 KM SRH AROUND 200 M2/S2/ ESP INVOF OF AN OUTFLOW
   BOUNDARY/STATIONARY FRONT ACROSS THE NEB/SD BORDER SUPPORTING THE
   THREAT FOR ISOLATED TORNADOES. THE INCREASING WAA MAY SUPPORT
   ISOLATED TSTMS JUST EAST OF WW 561...AS THE AIRMASS WAS
   DESTABILIZING AND MINIMAL CINH EXIST. TRENDS WILL BE MONITORED FOR
   ANOTHER WW IF THIS ACTIVITY INCREASES IN AREAL COVERAGE/STRENGTH
   OVER THE NEXT HOUR. FURTHER WEST...A CLUSTER OF TSTMS OVER FAR NERN
   WY/SERN MY MAY STRENGTHEN AND BEGIN TO POSE A SVR THREAT OVER WRN SD
   /WEST OF WW 561/. GIVEN THE LIMITED AREAL COVERAGE OF THE SVR THREAT
   OVER THIS AREA...A WW IS NOT EXPECTED.
   
   ..CROSBIE.. 08/03/2007
   
   
   ATTN...WFO...ABR...GID...LBF...UNR...CYS...
   
   43970202 43750203 43690295 42960295 42650271 41220262
   41240202 41410201 41380021 41030026 41039917 42989927
   42979957 43709955 43770080 43990103 44000193