MESOSCALE DISCUSSION 0524
   NWS STORM PREDICTION CENTER NORMAN OK
   1223 PM CDT THU MAY 08 2014

   AREAS AFFECTED...PARTS OF ERN NEBRASKA/SOUTH DAKOTA INTO SWRN
   MINNESOTA AND WRN/CNTRL IOWA

   CONCERNING...SEVERE POTENTIAL...WATCH LIKELY 

   VALID 081723Z - 081930Z

   PROBABILITY OF WATCH ISSUANCE...80 PERCENT

   SUMMARY...ORGANIZED BOUNDARY LAYER BASED STORM DEVELOPMENT APPEARS
   INCREASINGLY LIKELY BY 19-21Z.  THIS INCLUDES THE RISK FOR
   SUPERCELLS CAPABLE OF PRODUCING VERY LARGE HAIL...LOCALLY DAMAGING
   WIND GUSTS...AND TORNADOES.  ONE OR MORE WATCHES LIKELY WILL BE
   NEEDED.

   DISCUSSION...CONFIDENCE REMAINS LOW CONCERNING JUST HOW CONVECTIVE
   DEVELOPMENT WILL EVOLVE DURING THE NEXT SEVERAL HOURS.  HOWEVER...IT
   DOES APPEAR THAT...AS A VIGOROUS SHORT WAVE IMPULSE CONTINUES NORTH
   NORTHEASTWARD ACROSS CENTRAL NEBRASKA AND SOUTH DAKOTA...LARGE-SCALE
   FORCING FOR UPWARD VERTICAL MOTION WILL WEAKEN REMAINING INHIBITION
   FOR WARM SECTOR BOUNDARY LAYER PARCELS BY 19-21Z.  

   AS THE SURFACE CYCLONE CENTER REDEVELOPS NORTHEASTWARD FROM THE
   GRAND ISLAND NEB AREA TOWARD SIOUX CITY IA...THUNDERSTORMS DRIVEN BY
   LOWER/MID TROPOSPHERIC WARM ADVECTION ALREADY ARE UNDERWAY IN AN
   ARCING BAND FROM AROUND SIOUX FALLS SD INTO NORTHWEST IOWA.  AS THIS
   ACTIVITY SPREADS NORTHEASTWARD...POTENTIAL APPEARS TO EXIST FOR
   STORMS TO ROOT IN THE BOUNDARY LAYER...ALONG A SLOWLY RETREATING
   WARM FRONT NEAR THE IOWA/MINNESOTA BORDER...NORTH OF MASON CITY. 
   THIS MAY OCCUR COINCIDENT WITH A GRADUAL STRENGTHENING OF SOUTHERLY
   850 MB FLOW...WHICH COULD ENLARGE LOW-LEVEL HODOGRAPHS SUFFICIENTLY
   TO SUPPORT INCREASING TORNADO POTENTIAL BY 21-22Z.

   OTHERWISE...STRONG/SEVERE STORM DEVELOPMENT MAY BECOME FOCUSED NEAR
   THE MISSOURI RIVER...WHERE THE COLD FRONT OVERTAKES THE PRE-FRONTAL
   DRYLINE STRUCTURE...AND KINEMATIC AS WELL AS THERMODYNAMIC PROFILES
   ARE ALREADY FAVORABLE FOR SUPERCELLS.

   ..KERR/HART.. 05/08/2014


   ATTN...WFO...ARX...MPX...DMX...FSD...OAX...ABR...

   LAT...LON   42969730 44219726 45019691 45389516 44699319 43779279
               42559271 42219380 40979438 40709565 41729670 42969730