Potentially Significant Severe Event Monday
Posted by JAC on 6/19/2011, 5:42 am



DAY 2 CONVECTIVE OUTLOOK  
  NWS STORM PREDICTION CENTER NORMAN OK
  1235 AM CDT SUN JUN 19 2011
 
  VALID 201200Z - 211200Z
 
  ...THERE IS A MDT RISK OF SVR TSTMS ACROSS SERN SD/ERN NEB INTO
  EXTREME SRN MN AND MUCH OF WRN/NRN IA...
 
  ...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MDT RISK FROM
  THE SRN PLAINS INTO THE OH VALLEY...
 
  A POTENTIALLY SIGNIFICANT SEVERE WEATHER EVENT IS POSSIBLE ACROSS
  PARTS OF THE MID MO/MID MS VALLEY REGION MONDAY...INCLUDING THE
  POSSIBILITY OF TORNADOES AND VERY LARGE HAIL.  THE REGION MOST
  LIKELY TO RECEIVE SEVERE WEATHER WILL EXTEND FROM ERN NEB INTO NRN
  IA.
 
  ...MID MO/MID MS VALLEY...
 
  LATEST NAM/GFS DATA ARE IN REASONABLE AGREEMENT REGARDING THE
  EVOLUTION OF A SIGNIFICANT UPPER TROUGH AS IT SHIFTS ACROSS THE
  CNTRL ROCKIES INTO THE PLAINS MONDAY.  BOTH MODELS INSIST A STRONG
  MID LEVEL SPEED MAX...H5 APPROACHING 70KT...WILL ROUND THE BASE OF
  THE EJECTING TROUGH ACROSS THE TX PANHANDLE EARLY IN THE PERIOD THEN
  RACE NEWD INTO SERN NEB BY 21/00Z.  THIS FEATURE WILL UNDOUBTEDLY
  ENHANCE A FOCUSED ZONE OF ASCENT AHEAD OF A SFC CYCLONE THAT WILL
  MATURE ACROSS ERN NEB/SERN SD/NWRN IA DURING THE LATTER HALF OF THE
  PERIOD.
 
  WHILE A STRONG CAP WILL OVERSPREAD THE WARM SECTOR ACROSS MUCH OF
  THE MID MS VALLEY LATE DAY1 INTO THE DAY2 PERIOD...STRONG ASCENT
  WITHIN EXIT REGION OF UPPER JET WILL REMOVE INHIBITION AHEAD OF SFC
  LOW DURING FAVORABLE PEAK HEATING HOURS SUCH THAT INTENSE SUPERCELL
  DEVELOPMENT IS LIKELY WITHIN A VERY UNSTABLE AIR MASS...SBCAPE AOA
  4000 J/KG...CHARACTERIZED BY DEEP LAYER SHEAR IN EXCESS OF 50KT.
  FORECAST SOUNDINGS STRONGLY FAVOR THE POTENTIAL FOR TORNADOES WITH
  ACTIVITY THAT DEVELOPS AFTER 21Z AHEAD OF SFC LOW...EWD ALONG WARM
  FRONT INTO NRN IA.  IT APPEARS ACTIVITY MAY BE DELAYED EWD ALONG THE
  WARM FRONT UNTIL LATER IN THE EVENING HOURS.  EVEN SO...STRONG
  THERMODYNAMIC PARAMETERS...COUPLED WITH DYNAMIC EJECTING SPEED MAX
  SUGGEST TORNADIC SUPERCELLS COULD EASILY TRACK NEWD ACROSS ERN
  NEB/EXTREME SERN SD INTO NRN IA WHERE WARM ADVECTION WILL BE
  MAXIMIZED AFTER DARK.  THUS SEVERE CONVECTION SHOULD BE MAINTAINED
  WELL INTO THE OVERNIGHT HOURS.
 
  ...KS/OK...
 
  VERY HOT SFC TEMPERATURES WILL ONCE AGAIN BE NOTED SOUTH OF I-70
  ACROSS KS INTO OK WHERE READINGS WILL REBOUND ABOVE 100F IN MANY
  PLACES.  THIS DEEP BOUNDARY LAYER...COUPLED WITH SUPERCELL SHEAR
  PROFILES...WILL PROVE FAVORABLE FOR HIGH BASED STORMS CAPABLE OF
  PRODUCING LARGE HAIL AND DAMAGING WINDS.  CLOUD BASES MAY BE
  SOMEWHAT LOWER NORTH OF I-70 WHICH MAY INCREASE THE TORNADO THREAT
  FOR PORTIONS OF NERN KS...NWD.  OTHERWISE...HAIL/WIND SHOULD BE THE
  PRIMARY THREATS ALONG SRN PORTIONS OF OUTLOOK.
 
  ...OH VALLEY SEWD INTO THE SRN APPALACHIANS...
 
  STRONG LLJ ACROSS THE MID MS VALLEY EARLY IN THE PERIOD SHOULD PROVE
  RESPONSIBLE FOR THE MAINTENANCE OF AN MCS THAT SHOULD TRACK EWD INTO
  THE OH VALLEY DURING THE DAYLIGHT HOURS.  WHETHER THIS COMPLEX
  COMPLETELY DIMINISHES PRIOR TO DIURNAL REJUVENATION IS YET TO BE
  SEEN...EVEN SO REMNANT OUTFLOW AND ADEQUATE DEEP LAYER SHEAR WILL
  ENHANCE THE SEVERE THREAT WITH ANY STORMS THAT MATERIALIZE ACROSS
  THE OH VALLEY INTO THE CNTRL/SRN APPALACHIANS WHERE MID LEVEL FLOW
  VEERS MORE NWLY ALONG FRONT SIDE OF RIDGE AXIS.  IT/S NOT COMPLETELY
  CLEAR WHAT INFLUENCES LATE DAY1 CONVECTION WILL HAVE ACROSS THIS
  REGION BUT LEFT OVER CONVECTIVE DEBRIS AND REMNANT MCV/S COULD
  CERTAINLY MODULATE TSTM ACTIVITY WITHIN NWLY FLOW REGIME.
 
  ..DARROW.. 06/19/2011
 
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Strong Tornado Risk for Nebraska Sunday - JAC, 6/18/2011, 3:42 pm
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