MESOSCALE DISCUSSION 2074
   NWS STORM PREDICTION CENTER NORMAN OK
   0516 AM CDT SUN AUG 28 2011
   
   AREAS AFFECTED...PORTIONS CENTRAL/ERN SD...NERN NEB...EXTREME NWRN
   IA...EXTREME SWRN MN.
   
   CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 
   
   VALID 281016Z - 281245Z
   
   MCS MOVING FROM SRN ND INTO NRN SD CONTINUES TO BE MONITORED FOR
   INCREASING ORGANIZATION AND/OR UPSCALE GROWTH...WITH HAIL BEING MAIN
   THREAT.  SPORADIC DAMAGING WIND ALSO MAY BECOME
   POSSIBLE...ESPECIALLY IF ACTIVITY ORGANIZES DEEP COLD POOL WITH
   FORWARD-PROPAGATIONAL DOMINANCE OF STORM MOTION VECTOR.
   
   SFC MESOANALYSIS SHOWS FRONTAL ZONE HAS BECOME
   QUASISTATIONARY...EXTENDING SEWD FROM LOW NEAR 2WX ACROSS PHP AREA
   AND INTO ERN SANDHILLS OF NEB.  MAIN CONVECTIVE THREAT WILL REMAIN
   NE OF THIS FRONT...IN ZONE OF ENHANCED MID-UPPER LEVEL NWLYS AND
   RELATED 50-60 KT EFFECTIVE SHEAR MAGNITUDES.  MODIFIED RAOBS AND RUC
   SOUNDINGS INDICATE 1000-2000 J/KG MUCAPE ROOTED IN 750-850 MB LAYER
   ACROSS E-CENTRAL SD...WITHIN PROSPECTIVE CORRIDOR OF MCS MOTION SEWD
   ALONG GRADIENT IN ELEVATED BUOYANCY.  RELATIVELY STABLE LAYER NEAR
   SFC...AND NE OF FRONT...WILL BE MAINTAINED UNTIL A FEW HOURS AFTER
   SUNRISE.  WHILE THIS WILL LIMIT INTENSITY OF DOWNDRAFTS AT SFC...A
   FEW STG-SVR GUSTS MAY BE ACCELERATED SUFFICIENTLY THROUGH SUBCLOUD
   LAYER OF RELATIVELY LOW RH...SUCH THAT THEY CAN PENETRATE STABLE
   BOUNDARY LAYER.
   
   AHEAD OF MAIN TSTM COMPLEX...WIDELY SCATTERED TSTMS HAVE DEVELOPED
   IN LEADING EDGE OF FAVORABLE LARGE-SCALE ASCENT...PRIMARILY IN ZONE
   OF STG LOW-LEVEL WAA ACCOMPANYING BROAD/SWLY/15-25 KT FETCH AT 850
   MB.  THIS ACTIVITY WILL MOVE SEWD TOWARD PORTIONS NERN NEB AND NWRN
   IA WITH POTENTIAL FOR LARGE HAIL.  THOUGH DEEP-LAYER SHEAR IS WEAKER
   OVER SERN SD THAN FARTHER NW NEAR MCS...IT WILL STRENGTHEN WITH TIME
   AS SHORTWAVE TROUGH APCHS FROM ND.
   
   ..EDWARDS.. 08/28/2011
   
   
   ATTN...WFO...FSD...OAX...ABR...LBF...UNR...
   
   LAT...LON   45890024 45919924 45469814 44919716 44059590 43229631
               42439805 42599957 44050050 45550069 45890024