Apr 23, 2011 1630 UTC Day 1 Convective Outlook
Updated: Sat Apr 23 16:26:06 UTC 2011
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20110423 1630 UTC Day 1 Outlook Graphic
Probabilistic Tornado Graphic
20110423 1630 UTC Day 1 Tornado Probabilities 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
20110423 1630 UTC Day 1 Damaging Wind Probabilities 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
20110423 1630 UTC Day 1 Large Hail Probabilities 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 231622
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1122 AM CDT SAT APR 23 2011
   
   VALID 231630Z - 241200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS FROM CENTRAL TX INTO THE MID MS
   AND MUCH OF THE OH VALLEY...
   
   TODAYS UPPER PATTERN IS DOMINATED BY A LONG FETCH OF SOUTHWEST FLOW
   ALOFT FROM THE SOUTHWEST STATES INTO THE NORTHEAST.  A STRONG
   MID/UPPER LEVEL JET OVER THE GREAT LAKES REGION WILL MOVE INTO
   QUEBEC...LEAVING MUCH OF THE CENTRAL/EASTERN STATES WITH RATHER WEAK
   FORCING MECHANISMS ALOFT FOR ORGANIZED CONVECTIVE DEVELOPMENT. 
   NEVERTHELESS...A SURFACE FRONT EXTENDING FROM TX INTO THE UPPER OH
   VALLEY WILL PROVIDE THE FOCUS FOR THUNDERSTORMS TODAY AND TONIGHT.
   
   ...OH VALLEY...
   LATEST SURFACE ANALYSIS SHOWS THE MAIN SURFACE BAROCLINIC ZONE
   EXTENDING FROM NORTHERN AR NORTHEASTWARD ALONG THE OH RIVER INTO
   SOUTHERN OH.  SCATTERED SHOWERS AND THUNDERSTORMS HAVE BEEN ONGOING
   ALONG THIS AXIS OVERNIGHT...REINFORCING THE THERMAL/INSTABILITY
   GRADIENT.  RELATIVELY STRONG HEATING IS EXPECTED SOUTH OF THE
   BOUNDARY WHERE FORECAST SOUNDINGS SHOW MLCAPE VALUES AROUND 1500
   J/KG.  THE COMBINATION OF LOW LEVEL CONVERGENCE ALONG THE BOUNDARY
   AND A WEAK CAP TO ITS SOUTH WILL LEAD TO SCATTERED AFTERNOON STORMS.
    STEEP MID LEVEL LAPSE RATES AND EFFECTIVE DEEP-LAYER SHEAR OVER 40
   KNOTS WILL PROMOTE SUPERCELL STRUCTURES WITH LARGE HAIL AND DAMAGING
   WINDS THE MAIN THREATS.  LOW LEVEL SHEAR PROFILES ALSO SUPPORT SOME
   RISK OF TORNADOES THIS AFTERNOON AND EVENING.
   
   ...TX/OK/AR...
   A COLD FRONT IS SAGGING SLOWLY SOUTHWARD ACROSS OK AND NORTHWEST AR.
    THIS BOUNDARY SHOULD STALL BY EARLY AFTERNOON...WITH STRONG HEATING
   AND VERY UNSTABLE CONDITIONS DEVELOPING OVER SOUTHEAST OK/NORTHEAST
   TX AND PORTIONS OF WESTERN AR.  PRESENT INDICATIONS ARE THAT STORMS
   WILL DEVELOP RAPIDLY ALONG THE BOUNDARY BY LATE AFTERNOON AND SPREAD
   SOUTHEASTWARD INTO TX/AR THROUGH THE EVENING.  FORECAST SOUNDINGS
   SHOW AMPLE MOISTURE/CAPE AND BULK SHEAR VALUES OF 35-40
   KNOTS...FAVORABLE FOR SUPERCELLS.  THERMODYNAMIC PARAMETERS SUPPORT
   A RISK OF VERY LARGE HAIL ALONG AN AXIS FROM SOUTHEAST OK/NORTH
   CENTRAL TX INTO CENTRAL AR THIS AFTERNOON AND EVENING.
   
   LATER TONIGHT...LOW LEVEL WARM ADVECTION IS EXPECTED TO INTENSIFY
   ACROSS OK WHERE STEEP LAPSE RATES AND MODERATE ELEVATED CAPE WILL BE
   PRESENT.  SOME POTENTIAL FOR ELEVATED HAILSTORMS WILL EXIST TONIGHT
   ACROSS THIS REGION.
   
   ..HART/GARNER.. 04/23/2011
   
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