May 13, 2009 1300 UTC Day 1 Convective Outlook
Updated: Wed May 13 12:16:15 UTC 2009
Probabilistic to Categorical Outlook Conversion Table (Effective Feb 14, 2006).
Public Severe Weather Outlook

The SPC is forecasting ...severe thunderstorms expected from the central/southern plains to the mid mississippi valley later today and tonight....   Please read the latest public statement about this event.

Categorical Graphic
20090513 1300 UTC Day 1 Outlook Graphic
Probabilistic Tornado Graphic
20090513 1300 UTC Day 1 Tornado Probabilities Graphic
Torndao Legend Image
Probabilistic Damaging Wind Graphic
20090513 1300 UTC Day 1 Damaging Wind Probabilities Graphic
Wind Legend Image
Probabilistic Large Hail Graphic
20090513 1300 UTC Day 1 Large Hail Probabilities Graphic
Hail Legend Image
   SPC AC 131212
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0712 AM CDT WED MAY 13 2009
   
   VALID 131300Z - 141200Z
   
   ...THERE IS A MDT RISK OF SVR TSTMS THIS AFTERNOON AND EVENING OVER
   PARTS OF OK...SOUTHEAST KS...NORTHWEST AR...MUCH OF MO...AND MUCH OF
   IL...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS FROM PARTS OF THE
   CENTRAL/SOUTHERN PLAINS INTO THE MID MS VALLEY...
   
   A PROGRESSIVE SHORTWAVE TROUGH WILL TRACK RAPIDLY EASTWARD ACROSS
   THE NORTHERN HIGH PLAINS TODAY...WITH AN ASSOCIATED 90-100 KNOT MID
   LEVEL JET MAX NOSING INTO THE GREAT LAKES REGION BY TONIGHT.  AT THE
   SURFACE...A COLD FRONT WILL SWEEP EASTWARD INTO THE MID MS VALLEY BY
   AFTERNOON...TRAILING IN THE CENTRAL PLAINS.  THIS FRONT AND THE
   MOIST/UNSTABLE AIRMASS TO ITS SOUTHEAST WILL BE THE PRIMARY AREA OF
   CONCERN FOR SEVERE THUNDERSTORMS THIS AFTERNOON AND TONIGHT.  IT
   APPEARS THAT A LARGE AREA WILL SEE AN ACTIVE SEVERE WEATHER EVENT
   DURING THIS PERIOD.
   
   ...MO/IL THIS AFTERNOON...
   SATELLITE AND RADAR IMAGERY SHOW A WELL-DEFINED REMNANT MCV FROM
   LAST EVENINGS CONVECTION OVER TX/OK APPROACHING THE OK/AR BORDER. 
   THIS FEATURE IS EXPECTED TO CONTINUE MOVING EAST-NORTHEASTWARD AND
   BE OVER SOUTHEAST MO BY THIS AFTERNOON.  THE AIRMASS AHEAD OF THIS
   FEATURE WILL MOISTEN THROUGH THE DAY...WITH POCKETS OF DAYTIME
   HEATING LEADING TO A MODERATELY UNSTABLE AIRMASS /MLCAPE OF
   1000-2000 J/KG/.  FORCING ASSOCIATED WITH THE MCV WILL LIKELY BE
   SUFFICIENT FOR SCATTERED THUNDERSTORM DEVELOPMENT BY MID AFTERNOON
   OVER SOUTHERN MO AND SOUTHERN IL.  THESE STORMS MAY ALSO INTERACT
   WITH AN OUTFLOW BOUNDARY LEFT FROM THIS MORNINGS CONVECTION OVER IL.
   VERTICAL SHEAR WILL BE QUITE STRONG ACROSS THIS AREA...SUGGESTING
   THE RISK OF SUPERCELLS CAPABLE OF VERY LARGE HAIL AND TORNADOES. 
   SOME TORNADOES COULD BE STRONG WITH LONGER-LIVED DISCRETE SUPERCELLS
   THIS AFTERNOON.
   
   ...MO/IL THIS EVENING...
   BY LATE AFTERNOON...STRONG CONVERGENCE ALONG THE APPROACHING COLD
   FRONT WILL LIKELY RESULT IN NUMEROUS THUNDERSTORMS FROM CENTRAL IL
   INTO CENTRAL MO.  STRONG INSTABILITY AND SUFFICIENT VERTICAL SHEAR
   WILL PROMOTE BOW/LEWP STRUCTURES ALONG THE LINE CAPABLE OF LARGE
   HAIL AND DAMAGING WINDS.  TORNADOES WILL ALSO BE POSSIBLE IN
   ISOLATED SUPERCELLS AHEAD OF THE LINE.  CONVECTION WILL SPREAD
   SOUTHEASTWARD THROUGH THE NIGHT INTO SOUTHERN PARTS OF MO/IL WITH A
   CONTINUED RISK OF DAMAGING WINDS AND HAIL.
   
   ...KS/OK/AR THIS AFTERNOON AND EVENING...
   AN EXTREMELY UNSTABLE AIRMASS IS FORECAST TO DEVELOP OVER OK THIS
   AFTERNOON WITH DEWPOINTS NEAR 70...TEMPERATURES WELL INTO THE
   80S...AND NEAR DRY-ADIABATIC MID LEVEL LAPSE RATES.  MLCAPE VALUES
   OVER 4000 J/KG WILL BE COMMON ACROSS THE REGION...BUT A STRONG
   CAPPING INVERSION WILL SUPPRESS DEEP SURFACE-BASED CONVECTION
   THROUGH MOST OF THE DAY.  BY EARLY EVENING...DEEP BOUNDARY LAYER
   MIXING SHOULD BE SUFFICIENT FOR CONVECTIVE INITIATION ALONG THE
   DRYLINE OVER WESTERN OK.  OTHER STORMS WILL LIKELY DEVELOP AROUND
   THIS TIME ALONG THE COLD FRONT SAGGING INTO NORTHERN OK/SOUTHERN KS.
    VERTICAL SHEAR PROFILES WILL BE IMPROVING RAPIDLY DURING THIS TIME
   AS THE LOW LEVEL JET STRENGTHENS.  GIVEN THE DEGREE OF INSTABILITY
   AND SUFFICIENT EFFECTIVE SHEAR VALUES...LARGE SLOW-MOVING SUPERCELL
   STORMS CAPABLE OF VERY LARGE HAIL AND DAMAGING WINDS ARE EXPECTED. 
   SOME POTENTIAL WILL ALSO EXIST FOR ISOLATED TORNADOES...MAINLY AFTER
   DARK.  STORMS WILL CONGEAL INTO A LARGE MCS AND SPREAD SOUTHEASTWARD
   THROUGH THE NIGHT ACROSS MUCH OF OK AND INTO ADJACENT PARTS OF
   WESTERN MO/AR.
   
   ..HART/HURLBUT.. 05/13/2009
   
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   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z