DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0211 PM CDT WED APR 27 2011
   
   VALID 272000Z - 281200Z
   
   ...THERE IS A HIGH RISK OF SVR TSTMS LATE THIS AFTN AND EVE ACROSS
   PARTS OF NORTHERN AND EASTERN MISSISSIPPI...CENTRAL AND NORTHERN
   ALABAMA...NORTHWEST GEORGIA AND SOUTHERN TENNESSEE...
   
   ...THERE IS A MDT RISK OF SVR TSTMS SURROUNDING THE HIGH RISK
   AREA....ACROSS MUCH OF THE REMAINDER OF MISSISSIPPI...ALABAMA AND
   NORTHERN GEORGIA...THE WESTERN
   CAROLINAS...TENNESSEE...KENTUCKY...SOUTHEASTERN
   INDIANA...OHIO...PARTS OF WESTERN PENNSYLVANIA AND WEST VIRGINIA...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MODERATE RISK
   AREA...ACROSS MUCH OF THE EASTERN U.S....
   
   ...20Z OUTLOOK UPDATE...
   
   ...A DANGEROUS OUTBREAK OF SEVERE THUNDERSTORM AND TORNADOES APPEARS
   UNDERWAY...AND CONFIDENCE IS INCREASING THAT THIS WILL EXPAND
   NORTHWARD FROM THE GULF STATES THROUGH MUCH OF THE OHIO VALLEY LATE
   THIS AFTERNOON AND EVENING...
   
   REMNANTS OF THE MORNING MESOSCALE CONVECTIVE SYSTEM AND ITS
   ASSOCIATED SURFACE COLD POOL...JUST EAST OF UPPER PORTIONS OF THE
   LOWER MISSISSIPPI VALLEY INTO THE TENNESSEE VALLEY...REMAIN A
   COMPLICATING FACTOR CONCERNING CONVECTIVE POTENTIAL.  HOWEVER...
   LATEST OBSERVATIONAL DATA SUGGEST THAT THE COLD POOL MAY BE IN THE
   PROCESS OF WEAKENING.  AND BOUNDARY LAYER MOISTENING ASSOCIATED WITH
   THE PRECEDING RAINFALL...COUPLED WITH LATE AFTERNOON INSOLATION AND
   MODIFYING LOW-LEVEL THERMODYNAMIC PROFILES ASSOCIATED WITH STRONG
   DYNAMIC FORCING FOR UPWARD VERTICAL MOTION...PROBABLY WILL
   CONTRIBUTE TO SUFFICIENT DESTABILIZATION TO JUSTIFY EXPANDING
   MODERATE RISK SEVERE PROBABILITIES NORTHWESTWARD AND NORTHWARD
   THROUGH MUCH OF THE REMAINDER OF THE OHIO VALLEY.
   
   MODEL GUIDANCE...INCLUDING THE LATEST RUC AND 12Z ECMWF...INDICATE
   THAT A DEEP SURFACE CYCLONE WILL DEEPEN FURTHER AS IT MIGRATES
   NORTHWARD OUT OF THE OZARK PLATEAU...ACROSS THE LOWER OHIO VALLEY
   ...INTO THE LOWER GREAT LAKES REGION LATE THIS AFTERNOON AND
   TONIGHT.  THIS WILL ACCOMPANY A VIGOROUS MID-LEVEL SHORT WAVE
   IMPULSE...WHICH IS PROGGED TO CONTRIBUTE TO STRONG MID-LEVEL HEIGHT
   FALLS CENTERED ALONG THE OHIO RIVER...FROM NEAR ITS CONFLUENCE WITH
   THE MISSISSIPPI RIVER INTO THE CINCINNATI OH AREA BETWEEN 28/00-06Z.
    A 50-70 KT 850 MB JET APPEAR LIKELY TO DEVELOP  NORTHWARD TO THE
   WEST OF THE APPALACHIANS...AS A 100 KT 500 MB JET STREAK NOSES
   NORTHEASTWARD ACROSS KENTUCKY AND TENNESSEE INTO OHIO BY LATE THIS
   EVENING...CONTRIBUTING TO STRONG VERTICAL SHEAR SUPPORTIVE OF BOTH
   LONG-LIVED SUPERCELLS AND ORGANIZED STORM CLUSTERS.  GIVEN AT LEAST
   WEAK BOUNDARY LAYER DESTABILIZATION... STRONG TORNADOES APPEAR
   POSSIBLE...IN ADDITION TO THE RISK FOR STRONG /STRAIGHT LINE/
   DAMAGING CONVECTIVE GUSTS.
   
   ..KERR.. 04/27/2011