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