Categorical Graphic
Probabilistic Tornado Graphic
Probability of a tornado within 25 miles of a point. Hatched Area: 10% or greater probability of EF2 - EF5 tornadoes within 25 miles of a point.
Probabilistic Damaging Wind Graphic
Probability of damaging thunderstorm winds or wind gusts of 50 knots or higher within 25 miles of a point. Hatched Area: 10% of greater probability of wind gusts 65 knots or greater within 25 miles of a point.
Probabilistic Large Hail Graphic
Probability of hail 1" or larger within 25 miles of a point. Hatched Area: 10% or greater probability of hail 2" or larger within 25 miles of a point.

   SPC AC 302145
   
   DAY 1 CONVECTIVE OUTLOOK AMEND 1
   NWS STORM PREDICTION CENTER NORMAN OK
   0445 PM CDT MON MAY 30 2011
   
   VALID 302000Z - 311200Z
   
   ...THERE IS A MDT RISK OF SVR TSTMS LATE THIS AFTN AND EVE ACROSS
   PARTS OF CENTRAL AND EASTERN NEBRASKA...ERN SOUTH DAKOTA...NORTHWEST
   IOWA...WESTERN MINNESOTA AND A PARTS OF SOUTHEASTERN NORTH DAKOTA...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MODERATE RISK
   AREA...FROM THE CENTRAL PLAINS INTO THE UPPER MISSISSIPPI
   VALLEY/GREAT LAKES REGION...
   
   AMENDED FOR ADJUST SLIGHT RISK WESTWARD ACROSS PARTS OF SW
   NEBRASKA...NORTHEAST COLORADO
   
   ...AMENDMENT...
   REFER TO SEVERE THUNDERSTORM WATCH 404 FOR DETAILS.
   
   ...20Z UPDATE...
   ADJUSTMENTS TO THE CATEGORICAL AND PROBABILISTIC LINES HAVE BEEN
   MADE ...MOSTLY TO ACCOUNT FOR THE CURRENT POSITION OF THE SURFACE
   FRONT AND THE PRE-FRONTAL CORRIDOR OF STRONGER SURFACE HEATING AND
   BOUNDARY LAYER DESTABILIZATION.  THIS HAS GENERALLY RESULTED IN A 
   SOUTHEASTWARD DISPLACEMENT OF HIGHEST SEVERE PROBABILITIES RELATIVE
   TO THE 1630Z OUTLOOK.
   
   OTHERWISE...FORECAST REASONING REMAINS GENERALLY UNCHANGED FROM THAT
   INDICATED IN THE PRIOR DISCUSSION AND APPENDED BELOW.  AS A
   SIGNIFICANT UPPER TROUGH AND EMBEDDED CLOSED LOW CONTINUE TO
   GRADUALLY LIFT NORTH NORTHEAST OF THE ROCKIES LATE THIS AFTERNOON
   ...ASSOCIATED FORCING FOR UPWARD VERTICAL MOTION APPEARS LIKELY TO
   WEAKEN INHIBITION IN SUCH A MANNER AS TO ALLOW RAPID WIDESPREAD
   STORM FORMATION WITHIN THE DEVELOPING INSTABILITY AXIS.
   
   IF STORMS MAINTAIN A DISCRETE NATURE AS THE SOUTHERLY PRE-FRONTAL
   LOW-LEVEL JET INTENSIFIES THIS EVENING /GUIDANCE INDICATES UP TO
   AROUND 70+ KT AT 850 MB/...VERY LARGE CLOCKWISE-CURVED LOW-LEVEL
   HODOGRAPHS WILL SUPPORT A RISK FOR STRONG TORNADOES.  HOWEVER... IT
   STILL APPEARS THAT THE WINDOW OF OPPORTUNITY FOR THIS MAY BE FAIRLY
   SMALL...WITH LARGE-SCALE FORCING LIKELY TO CONTRIBUTE TO A QUICK
   UPSCALE CONVECTIVE GROWTH INTO ONE OR MORE ORGANIZED STORM CLUSTERS
   CAPABLE OF PRODUCING LOCALLY STRONG TO EXTREME SURFACE
   GUSTS...PARTICULARLY ACROSS EASTERN PORTIONS OF THE MODERATE RISK
   AREA.
   
   ..KERR.. 05/30/2011
   
   .PREV DISCUSSION... /ISSUED 1121 AM CDT MON MAY 30 2011/
   
   A BROAD UPPER TROUGH IS PRESENT TODAY OVER THE WESTERN STATES...WITH
   A SHORTWAVE TROUGH EVIDENT IN WATER VAPOR IMAGERY ROUNDING THE BASE
   OF THE TROUGH OVER NM.  THIS FEATURE WILL LIFT NORTHWARD ACROSS THE
   HIGH PLAINS THIS AFTERNOON AND EVENING...LEADING TO AN ACTIVE ZONE
   OF SEVERE THUNDERSTORMS FROM CENTRAL KS INTO THE DAKOTAS AND WESTERN
   MN.
   
   ...NEB/DAKOTAS/MN...
   A WEAK SURFACE COLD FRONT CURRENTLY EXTENDS FROM SOUTHEAST ND INTO
   NORTH CENTRAL NEB.  THIS FRONT WILL MOVE ONLY SLOWLY SOUTHEASTWARD
   TODAY...AND WILL LIKELY RETREAT NORTHWARD LATER TODAY OVER ND/MN AS
   CYCLOGENESIS OCCURS OVER THE REGION.  THE FRONT WILL SERVE AS THE
   PRIMARY FOCUS FOR THUNDERSTORM INITIATION THIS AFTERNOON AS FULL
   SUNSHINE OCCURS IN THE WARM SECTOR.  AFTERNOON MLCAPE VALUES OF
   3000+ J/KG ARE EXPECTED...ALONG WITH A NARROW AXIS OF WEAK CINH
   ALONG THE FRONT.
   
   PRESENT INDICATIONS ARE THAT STORMS WILL FORM ON THE FRONT AROUND
   21Z FROM THE TRIPLE POINT OVER CENTRAL NEB NORTHWARD INTO THE
   EASTERN DAKOTAS.  STRONG WINDS THROUGH THE TROPOSPHERE WILL PROMOTE
   SUPERCELL STORM STRUCTURES.  HOWEVER...ORIENTATION OF FRONT TO UPPER
   WINDS MAKE STORM-MODE FORECASTS COMPLEX.  INITIAL STORMS MAY POSE A
   RISK OF TORNADOES.  BUT A RATHER QUICK EVOLUTION TO A SQUALL LINE
   APPEARS LIKELY WITH EMBEDDED BOWS POSSIBLE.  THROUGH THE
   EVENING...LARGE HAIL AND DAMAGING WINDS ARE EXPECTED ALONG THE
   SQUALL LINE AS IT MOVES INTO WESTERN NEB AND NORTHWEST IA.  
   
   ...KS SOUTHWARD ACROSS THE HIGH PLAINS...
   THE DRYLINE WILL EXTEND FROM CENTRAL NEB SOUTHWARD INTO WESTERN OK
   AND WEST TX.  THE POTENTIAL FOR CONVECTIVE INITIATION THIS AFTERNOON
   AND EVENING IS HIGHEST NEAR THE TRIPLE POINT OVER NEB/NORTHERN
   KS...AND DECREASES WITH SOUTHWARD EXTENT.  STORMS THAT FORM OVER
   NEB/KS WILL POSE A RISK OF LARGE HAIL...DAMAGING WINDS...AND PERHAPS
   A TORNADO.  HOWEVER...THERE REMAINS CONSIDERABLE UNCERTAINTY
   REGARDING COVERAGE AND LONGEVITY OF STORMS.  FROM WESTERN OK INTO
   WEST TX...ONLY VERY ISOLATED DRYLINE STORMS ARE EXPECTED.
   
   CLICK TO GET WUUS01 PTSDY1 PRODUCT

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z