Apr 26, 2011 1730 UTC Day 2 Convective Outlook
Updated: Tue Apr 26 17:32:01 UTC 2011
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20110426 1730 UTC Day 2 Outlook Graphic
Probabilistic Graphic
20110426 1730 UTC Day Probabilitic Graphic
Probability of severe weather within 25 miles of a point.
Hatched Area: 10% or greater probability of significant severe within 25 miles of a point.
   SPC AC 261730
   
   DAY 2 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1230 PM CDT TUE APR 26 2011
   
   VALID 271200Z - 281200Z
   
   ...THERE IS A MDT RISK OF SVR TSTMS WEDNESDAY ACROSS PARTS OF
   EASTERN INDIANA...MUCH OF OHIO...WESTERN PENNSYLVANIA...WEST
   VIRGINIA...MUCH OF KENTUCKY AND TENNESSEE...NORTHEAST
   GEORGIA...CENTRAL AND NORTHERN ALABAMA AND MISSISSIPPI...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MODERATE RISK
   AREA ACROSS MUCH OF THE EASTERN U.S....
   
   ...SYNOPSIS...
   ...OUTBREAK OF SEVERE THUNDERSTORMS POSSIBLE...
   MODELS INDICATE THAT THE LARGE UPPER TROUGH...NOW EVOLVING OVER THE
   CENTRAL U.S...WILL SLOWLY LIFT ACROSS AND EAST OF THE MISSISSIPPI
   VALLEY DURING THIS PERIOD.  AS IT DOES...IT APPEARS LIKELY TO TAKE
   ON AN INCREASING NEGATIVE TILT...AS A STRONG SHORT WAVE IMPULSE
   LIFTS OUT OF ITS BASE...AND GRADUALLY PIVOTS AROUND THE EASTERN
   PERIPHERY OF A DEVELOPING CYCLONIC CIRCULATION OVER THE UPPER
   MISSISSIPPI VALLEY/GREAT LAKES REGION.  THIS SHOULD BE ACCOMPANIED
   BY STRENGTHENING CYCLONIC MID/UPPER FLOW FIELDS IN THE WARM SECTOR
   OF A SURFACE CYCLONE PROGGED TO DEEPEN AS IT MIGRATES NORTHEAST OF
   THE OZARK PLATEAU TOWARD THE GREAT LAKES.  THIS PROBABLY WILL
   INCLUDE A 90-100 KT 500 MB JET CORE NOSING ACROSS THE TENNESSEE AND
   OHIO VALLEYS BY LATE AFTERNOON.
   
   VARIABILITY EXISTS AMONG THE MODELS CONCERNING THE DETAILS OF THIS
   CYCLOGENESIS...PERHAPS IN PART DUE TO THE INFLUENCE OF CONVECTION
   ...WHICH COULD BE EXTENSIVE AND ONGOING AT 12Z WEDNESDAY.  HIGH
   RESOLUTION MODEL DATA IS STRONGLY SUGGESTIVE THAT A SIGNIFICANT
   CLUSTER OF STORMS COULD BE IN PROGRESS WEDNESDAY MORNING EAST OF THE
   MIDDLE AND LOWER MISSISSIPPI VALLEY.  IF THIS VERIFIES...IT IS
   UNCERTAIN WHAT INFLUENCE IT WILL HAVE ON SUBSEQUENT BOUNDARY LAYER
   DESTABILIZATION ACROSS THE OHIO/TENNESSEE VALLEY REGION.  THIS
   UNCERTAINTY PRECLUDES AN OUTLOOK UPGRADE TO HIGH RISK PROBABILITIES
   AT THE PRESENT TIME.  HOWEVER...MOST OTHER INDICATIONS ARE STRONGLY
   SUGGESTIVE THAT A MAJOR OUTBREAK OF SEVERE THUNDERSTORMS COMMENCING
   TONIGHT ACROSS PARTS OF THE OZARK PLATEAU/LOWER MISSISSIPPI VALLEY
   WILL CONTINUE AND EXPAND NORTHWARD AND EASTWARD TOWARD THE
   APPALACHIANS DURING THE DAY WEDNESDAY.  THIS WILL INCLUDE THE
   POTENTIAL FOR LONG-LIVED SUPERCELLS CAPABLE OF STRONG
   TORNADOES...AND ORGANIZED STORM CLUSTERS CAPABLE OF STRONG DAMAGING
   WIND GUSTS.
   
   ...EASTERN U.S...
   IN AREAS NOT IMPACTED SIGNIFICANTLY BY EARLY MORNING CONVECTION...
   PRE-FRONTAL BOUNDARY LAYER MOISTURE OVER A BROAD AREA EAST OF THE
   MISSISSIPPI VALLEY INTO THE APPALACHIANS...AND PERHAPS EAST OF THE
   APPALACHIANS...WILL BE SUPPORTIVE OF CAPE ON THE ORDER OF 1000 TO
   2000 J/KG WITH SURFACE HEATING.  IN THE PRESENCE OF WIND PROFILES
   CHARACTERIZED BY STRONG DEEP LAYER SHEAR...AND LARGE CLOCKWISE
   CURVED LOW-LEVEL HODOGRAPHS BENEATH A BROAD 50-70 KT SOUTHERLY
   LOW-LEVEL JET...A SIGNIFICANT TORNADIC SUPERCELL THREAT COULD BE
   ONGOING OR RAPIDLY DEVELOP BY LATE MORNING ACROSS PARTS OF
   NORTHEASTERN MISSISSIPPI/NORTHERN ALABAMA THROUGH WESTERN/MIDDLE
   TENNESSEE AND WESTERN/CENTRAL KENTUCKY.  HOWEVER...THIS WILL BE
   LARGELY CONTINGENT ON EVOLUTION OF OVERNIGHT CONVECTION.  IF AN
   LARGE CLUSTER OF STORMS DEVELOPS AS SOME GUIDANCE SUGGESTS...AN
   EXPANSIVE SURFACE COLD POOL COULD SLOW DESTABILIZATION AND MITIGATE
   THE SEVERE POTENTIAL.
   
   REGARDLESS...SUFFICIENT WEAKENING OF THE CONVECTION AND THE
   ASSOCIATED COLD POOL IS EXPECTED TO OCCUR BY THE AFTERNOON TO
   SUPPORT WEAK TO MODERATE DESTABILIZATION IN THE PRESENCE OF
   STRENGTHENING LARGE-SCALE FORCING FOR UPWARD VERTICAL MOTION.  AND
   THIS PROBABLY WILL BE SUFFICIENT TO SUPPORT CONVECTIVE
   DEVELOPMENT...INCLUDING TORNADIC SUPERCELLS...IN THE WARM SECTOR
   ...AND ALONG AND AHEAD OF THE COLD FRONT TRAILING SOUTHWARD FROM THE
   SURFACE LOW.  AS THIS FRONT ADVANCES TOWARD THE APPALACHIANS
   ...UPSCALE CONVECTIVE GROWTH INTO AN EXTENSIVE SQUALL LINE COULD
   OCCUR BY EARLY WEDNESDAY EVENING...BEFORE SPREADING EAST OF THE
   APPALACHIANS OVERNIGHT.
   
   ..KERR.. 04/26/2011
   
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   NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 0600Z