MESOSCALE DISCUSSION 1034
   NWS STORM PREDICTION CENTER NORMAN OK
   0617 PM CDT MON MAY 30 2011
   
   AREAS AFFECTED...PORTIONS SERN ND...CENTRAL NEB...ERN
   SD...WRN-CENTRAL MN.
   
   CONCERNING...TORNADO WATCH 402...403...
   
   VALID 302317Z - 310115Z
   
   THE SEVERE WEATHER THREAT FOR TORNADO WATCH 402...403...CONTINUES.
   
   AT 2230Z...CONVENTIONAL AND REFLECTIVITY DATA INDICATES SFC COLD
   FRONT EXTENDING SWD FROM SERN ND LOW ACROSS ERN SD BETWEEN
   MHE-ATY...THEN SSWWD ACROSS HOLT/CUSTER COUNTIES NEB...INTERSECTING
   DRYLINE BETWEEN LBF-BBW.  DRYLINE WAS ANALYZED SWD FROM THERE ACROSS
   FRONTIER COUNTY NEB AND GRAY COUNTY KS...AND SHOULD RETREAT/MERGE
   WITH COLD FRONT OVER SERN NEB DURING NEXT FEW HOURS.  THIS PROCESS
   MAY BE ACCELERATED AS COMBINED GRADIENT WINDS AND TSTM OUTFLOW OVER
   WW 404--SEE MESOSCALE DISCUSSION 1033--MOVE EWD ACROSS WRN NEB INTO
   SRN PORTIONS WW 402.
   
   BAND OF STG-SVR TSTMS FROM FRONT-DRYLINE INTERSECTION NEWD TO SERN
   SD...WITH ADDITIONAL ACTIVITY MOVING MORE NWD BEHIND COLD FRONT. 
   APPARENT HEAVY-PRECIP SUPERCELL HAS PRODUCED A FEW TORNADO REPORTS
   ACROSS PORTIONS ROCK/BLAINE/HOLT COUNTIES NEB DURING PAST 1-2
   HOURS...AS WELL AS VERY LARGE/DAMAGING HAIL UP TO 3.5 INCHES
   DIAMETER.  SIMILAR THREATS WILL PERSIST FOR THIS OR ANY OTHER CELLS
   THAT CAN REMAIN SOMEWHAT DISCRETE OR MAINTAIN SEWD EXTENSIONS INTO
   RELATIVELY UNIMPEDED WARM-SECTOR INFLOW AIR.  PREFRONTAL AIR MASS
   WILL BE CHARACTERIZED BY MID 60S TO NEAR 70 F DEW POINTS...WITH
   MLCAPE 2500-4000 J/KG AND MINIMAL CINH FOR ANOTHER FEW HOURS...AND
   50-60 KT EFFECTIVE SHEAR MAGNITUDES.  THOUGH SRH WILL REMAIN LARGEST
   ALONG WARM FRONT NOW MOVING NWD BEYOND FAR/DTL/MSP AREAS...FAVORABLE
   LOW-LEVEL SHEAR FOR SUPERCELLS AND OCNL TORNADOES WILL PERSIST SWWD
   ACROSS ERN SD AND CENTRAL NEB.
   
   UPSCALE GROWTH AND MORE LINEAR EVOLUTION STILL APPEARS LIKELY GIVEN
   SMALLNESS OF MEAN-WIND AND DEEP-SHEAR VECTOR ANGLES WITH RESPECT TO
   COLD FRONTAL ZONE.  GIVEN PROGRESS OF SFC COLD FRONT...ANY STORM
   MOTION VECTORS ALONG FRONT AND CERTAINLY TO ITS W WILL REMAIN
   LEFTWARD OF FRONT...AND THEREFORE ATOP BOUNDARY LAYER WITH
   SUBSTANTIALLY LOWER THETAE AND STRONGER MLCINH.  ELEVATED BUOYANCY
   AVAILABLE TO THIS ACTIVITY STILL SHOULD BE SUFFICIENT TO SUPPORT
   LARGE HAIL THREAT...AND SHALLOWNESS OF STABLE LAYER JUST W OF FRONT
   SHOULD NOT PRECLUDE OCNL DAMAGING GUSTS AS WELL.  MLCINH ESTIMATES
   INCREASE TO AOA 200 J/KG IN PROGRESSIVELY MORE STABLE POST-FRONTAL
   AIR W OF ABOUT 9V9-ABR LINE.
   
   ..EDWARDS.. 05/30/2011
   
   
   ATTN...WFO...DLH...MPX...FGF...FSD...OAX...ABR...GID...BIS...
   LBF...UNR...GLD...
   
   LAT...LON   41900027 43679954 44609905 46589801 47699677 47189444
               44819467 43389640 41629756 40319819 40210083 41900027