SPC AC 181254
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0754 AM CDT SAT MAY 18 2013
   
   VALID 181300Z - 191200Z
   
   ...THERE IS A MDT RISK OF SVR TSTMS THIS AFTERNOON AND EVENING OVER
   PORTIONS OF SOUTHWEST NEB...WESTERN KS...AND WESTERN OK...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS MUCH OF THE GREAT PLAINS
   AND UPPER MIDWEST...
   
   ...ACTIVE SEVERE WEATHER EVENT EXPECTED ACROSS PARTS OF NEB/KS/OK
   LATER THIS AFTERNOON AND EVENING...
   
   ...NEB/KS/OK...
   MORNING WATER VAPOR LOOPS SHOW A BROAD UPPER TROUGH OVER THE WESTERN
   STATES...WITH SEVERAL SHORTWAVE TROUGHS EMBEDDED IN THE CYCLONIC
   FLOW.  ONE SHORTWAVE TROUGH CURRENTLY OVER WESTERN AZ IS EXPECTED TO
   EMERGE INTO THE CENTRAL PLAINS THIS EVENING...PROVIDING THE FOCUS
   FOR SEVERE THUNDERSTORM DEVELOPMENT.  AHEAD OF THE
   TROUGH...SOUTHERLY LOW LEVEL WINDS WILL MAINTAIN AMPLE MOISTURE
   ACROSS THE PLAINS WITH 60S TO LOWER 70S DEWPOINTS EXPECTED FROM
   CENTRAL/WESTERN KS INTO OK AND NORTH TX.  THE DRYLINE IS FORECAST TO
   BECOME ESTABLISHED FROM WESTERN OK INTO THE EXTREME EASTERN TX
   PANHANDLE BY MID/LATE AFTERNOON.  STRONG HEATING AND DEEP MIXING
   BEHIND THE DRYLINE COUPLED WITH WEAK BUT SUSTAINED LARGE SCALE
   ASCENT ASSOCIATED WITH THE WESTERN TROUGH WILL EVENTUALLY ERODE THE
   CAP.  RAPID THUNDERSTORM DEVELOPMENT WILL BEGIN OVER WESTERN KS BY
   20Z...WITH ACTIVITY DEVELOPING SOUTHWARD ALONG THE OK/TX PANHANDLE
   BORDER BY LATE AFTERNOON.  FAVORABLE EFFECTIVE SHEAR AND VERY HIGH
   CAPE VALUES /MLCAPE OF 3500+ J/KG/ WILL PROMOTE SUPERCELLS CAPABLE
   OF VERY LARGE HAIL.  LCL HEIGHTS AND LOW LEVEL SHEAR ARE NOT
   FORECAST TO BE PARTICULARLY FAVORABLE FOR TORNADOES...BUT DEGREE OF
   INSTABILITY MAY COMPENSATE FOR NEGATIVE FACTORS SO HAVE MAINTAINED
   RISK OF ISOLATED STRONG TORNADOES ACROSS MUCH OF THE MODERATE RISK
   AREA.  THUNDERSTORMS ARE LIKELY TO GROW UPSCALE THROUGH THE EVENING
   AS A BROKEN LINE MOVES EASTWARD INTO CENTRAL KS AND NORTH-CENTRAL OK
   WITH AN INCREASED RISK OF DAMAGING WINDS.
   
   ...TX...
   SEVERAL MODEL SOLUTIONS INDICATE THAT AT LEAST WIDELY SCATTERED
   THUNDERSTORMS WILL DEVELOP BY LATE AFTERNOON ALONG THE
   DRYLINE...PERHAPS AS FAR SOUTH AS DYS/BWD.  FORCING WILL BE WEAK BUT
   STRONGER THAN YESTERDAY.  ANY STORM THAT FORMS ALONG THE CORRIDOR
   WILL LIKELY BECOME SUPERCELLULAR WITH A RISK OF VERY LARGE HAIL AND
   DAMAGING WINDS.
   
   ...SD/ND/MN/IA...
   MULTIPLE CLUSTERS OF THUNDERSTORMS ARE ONGOING THIS MORNING OVER
   EASTERN SD INTO MN/WI.  SOME INTENSIFICATION IS POSSIBLE ALONG THE
   LEADING EDGE OF THIS ACTIVITY LATER THIS MORNING...BUT THE PRIMARY
   SEVERE THREAT WILL LIKELY OCCUR LATE THIS AFTERNOON AND EVENING AS
   NEW STORMS FORM OVER NEB/SD AND SPREAD EAST-NORTHEASTWARD.  DETAILS
   OF CONVECTIVE EVOLUTION ARE UNCLEAR AT THIS TIME DUE TO ONGOING
   STORMS...BUT IT APPEARS THAT HAIL AND DAMAGING WINDS WILL BE
   POSSIBLE WITH STRONGER STORMS ACROSS MUCH OF THE NORTHERN PLAINS AND
   UPPER MIDWEST LATER TODAY.
   
   ...SOUTHEAST STATES...
   A REMNANT UPPER TROUGH REMAINS OVER THE TN VALLEY AND SOUTHEAST
   STATES TODAY.  THIS WILL LEAD TO ANOTHER DAY OF SCATTERED
   THUNDERSTORMS OVER A RELATIVELY LARGE AREA.  IT APPEARS THE CORRIDOR
   MOST LIKELY TO SEE A FEW STRONG STORMS WILL BE FROM CENTRAL AL INTO
   SOUTHWEST GA AND NORTH FL WHERE STRONG HEATING/DESTABILIZATION WILL
   OCCUR.  STORMS CURRENTLY OVER CENTRAL AL ARE EXPECTED TO SPREAD
   SOUTHEASTWARD ACROSS THIS REGION POSING A RISK OF LOCALLY DAMAGING
   WINDS AND HAIL.
   
   ..HART/LEITMAN.. 05/18/2013
   
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