MAJOR TORNADO OUTBREAK IS FORECAST
Posted by JAC on 5/25/2011, 12:50 pm
http://www.spc.noaa.gov/products/outlook/day1otlk.html

DAY 1 CONVECTIVE OUTLOOK  
  NWS STORM PREDICTION CENTER NORMAN OK
  1123 AM CDT WED MAY 25 2011
 
  VALID 251630Z - 261200Z
 
  ...THERE IS A HIGH RISK OF SVR TSTMS THIS AFTERNOON INTO EARLY
  TONIGHT OVER PARTS OF NORTHEAST AR...WEST TN...SOUTHEAST
  MO...SOUTHERN IL...WESTERN AND CENTRAL KY...AND SOUTHERN IND...
 
  ...THERE IS A MDT RISK OF SVR TSTMS FROM SOUTHERN AR AND NORTHERN MS
  ACROSS MUCH OF THE MID MS/OH AND TN RIVER VALLEYS...
 
  ...THERE IS A SLGT RISK OF SVR TSTMS FROM NORTHERN LA INTO THE
  EASTERN GREAT LAKES...
 
  ...MAJOR TORNADO OUTBREAK IS FORECAST LATER TODAY AND TONIGHT OVER
  PORTIONS OF THE MID MS AND LOWER OH VALLEYS...
 
  A STRONG UPPER LOW OVER KS WILL MOVE SLOWLY EASTWARD TODAY...WHILE A
  SHORTWAVE TROUGH ROTATES AROUND THE SOUTHERN PERIPHERY OF THE LOW
  INTO THE MID MS AND LOWER OH VALLEYS.  A LARGE BAND OF 70+ KNOT
  WESTERLY MID LEVEL WINDS STRETCH FROM OK/TX INTO IL/KY/TN THIS
  MORNING...ACROSS A LARGE/MOIST WARM SECTOR.  AN EXPANSIVE AREA OF
  MID/UPPER 60S DEWPOINTS EXTEND FROM THE COLD FRONT OVER WRN MO/AR
  EASTWARD TO EASTERN KY AND NORTHWARD INTO NORTHERN IND.  THE RESULT
  WILL BE A VERY DANGEROUS RISK OF WIDESPREAD SEVERE THUNDERSTORMS
  LATER THIS AFTERNOON AND EVENING...INCLUDING LONG-DURATION
  STRONG/VIOLENT TORNADOES.
 
  MORNING RAOBS AND FORECAST SOUNDINGS SUGGEST THAT WIDESPREAD MOIST
  AND VERY UNSTABLE CONDITIONS WILL BE PRESENT ACROSS THE WARM SECTOR
  TODAY.  BROKEN CLOUDS WILL YIELD AFTERNOON MLCAPE VALUES OF
  2500-3500 J/KG OVER A LARGE AREA...ALONG WITH A RELATIVELY WEAK CAP.
   THIS WILL RESULT IN THE POTENTIAL FOR MULTIPLE ROUNDS OF SEVERE
  THUNDERSTORMS ACROSS THE AREA...BOTH IN THE WARM SECTOR...AND ALONG
  THE SURFACE COLD FRONT AS IT SWEEPS EASTWARD LATER TODAY.
 
  TCU AND THUNDERSTORMS HAVE BEGUN TO DEVELOP AHEAD OF THE UPPER LOW
  AND NEAR THE COLD FRONT OVER WESTERN MO/AR.  THE 15Z SGF RAOB SHOWS
  FAVORABLE VERTICAL SHEAR PROFILES FOR SUPERCELL THUNDERSTORMS
  CAPABLE OF VERY LARGE HAIL AND TORNADOES.  THESE STORMS SHOULD
  INTENSIFY THROUGH THE DAY WITH AN INCREASING RISK OF STRONG/VIOLENT
  TORNADOES.  ONCE THESE STORMS BECOME ESTABLISHED...THEY MAY PERSIST
  THROUGH MUCH OF THE FORECAST PERIOD AND SURGE EASTWARD ACROSS THE
  MDT/HIGH RISK AREAS.
 
  FARTHER EAST...SEVERAL MODEL SOLUTIONS INDICATE THE DEVELOPMENT OF
  CONVECTION IN THE WARM SECTOR OVER PORTIONS OF NORTHEAST
  AR/SOUTHEAST MO/SOUTHERN IL/WESTERN KY...SPREADING INTO WEST TN AND
  SOUTHERN IND.  0-3KM SRH VALUES OF 250-400 M2/S2 COUPLED WITH LONG
  HODOGRAPHS AND HIGH INSTABILITY SUGGEST THESE STORMS WOULD LIKELY BE
  DISCRETE SUPERCELLS WITH AN INCREASING RISK OF MULTIPLE
  STRONG/VIOLENT TORNADOES AND VERY LARGE HAIL.
 
  DURING THE EVENING...MULTIPLE LINES/CLUSTERS OF INTENSE/SUPERCELL
  STORMS AND BOWS MAY BE TRACKING RAPIDLY EAST-NORTHEASTWARD ACROSS
  THE MDT/HIGH RISK AREAS.  GIVEN THE LARGE AREA POTENTIALLY AFFECTED
  BY SEVERE STORMS TODAY...THE STRENGTH OF THE LOW AND DEEP LAYER
  SHEAR...AND THE STRONG INSTABILITY...THE POTENTIAL IS INCREASING FOR
  A MAJOR TORNADO OUTBREAK.  WIDESPREAD WIND DAMAGE AND LARGE HAIL ARE
  ALSO A PROMINENT CONCERN THROUGH THE EVENING HOURS.
 
  BY MID TO LATE EVENING...THUNDERSTORMS ARE LIKELY TO DEVELOP
  SOUTHWARD ALONG THE COLD FRONT INTO SOUTHERN AR/NORTHERN LA.  THIS
  ACTIVITY WILL BE NEAR THE NOSE OF A STRONG WESTERLY MID LEVEL
  JET...AND MAY POSE A RISK OF SIGNIFICANT SEVERE WEATHER AS WELL.
  UNCERTAINTY EXISTS REGARDING THE COVERAGE OF STORMS IN THIS
  AREA...BUT NONETHELESS HAVE EXTENDED THE MDT RISK SLIGHTLY FARTHER
  SOUTH TO HIGHLIGHT THIS THREAT.
 
  ..HART/GRAMS.. 05/25/2011
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Mid MS-River Area under High-Risk for Severe Weather Today - JAC, 5/25/2011, 9:01 am
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