SPC Discussion for Sunday
Posted by JAC on 4/8/2011, 7:57 am



DAY 3 CONVECTIVE OUTLOOK CORR 1
  NWS STORM PREDICTION CENTER NORMAN OK
  0246 AM CDT FRI APR 08 2011
 
  VALID 101200Z - 111200Z
 
  ...THERE IS A MDT RISK OF SVR TSTMS ACROSS PARTS OF SE
  MN...WI...ECNTRL IA...NW IL AND FAR NE MO...
 
  ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE UPPER MS
  VALLEY...MID-MS VALLEY...OZARKS AND SRN PLAINS...
 
  CORRECTED TO EXTEND MDT RISK AREA FURTHER INTO SE MN AND NRN IA TO
  MATCH PROBABILITIES
 
  ...UPPER MS VALLEY/WRN GREAT LAKES...
  AN IMPRESSIVE UPPER-LEVEL TROUGH IS FORECAST TO MOVE INTO THE CNTRL
  PLAINS SUNDAY WITH AN UPPER-LEVEL LOW CLOSING OFF OVER THE NRN
  PLAINS. AHEAD OF THE SYSTEM...A POWERFUL 55 TO 70 KT JET WILL
  TRANSPORT LOW-LEVEL MOISTURE QUICKLY NWD INTO THE UPPER MS VALLEY
  WHERE SFC DEWPOINTS SHOULD REACH THE LOWER TO MID 60S F. THIS SHOULD
  ALLOW MODERATE INSTABILITY TO DEVELOP ACROSS MUCH OF THE UPPER
  MIDWEST BY SUNDAY AFTERNOON WHERE NUMEROUS THUNDERSTORMS APPEAR
  LIKELY TO DEVELOP AS LARGE-SCALE ASCENT INCREASES DURING THE
  AFTERNOON. THUNDERSTORMS SHOULD FIRST DEVELOP DURING THE AFTERNOON
  ALONG A WARM FRONT ACROSS IA...WI AND SRN MN WITH ADDITIONAL
  CONVECTION INITIATING ALONG THE COLD FRONT DURING THE EARLY EVENING
  EXTENDING SWD INTO NW MO. THIS IS EXPECTED AS THE EXIT REGION OF THE
  AN IMPRESSIVE 80 TO 100 KT MID-LEVEL JET SPREADS ACROSS THE
  UPPER-MIDWEST CREATING STRONG DEEP LAYER SHEAR AND VERY FAVORABLE
  CONDITIONS FOR SEVERE STORMS. THIS COMBINED WITH STRONG LOW-LEVEL
  SHEAR PROFILES SHOULD BE FAVORABLE FOR SUPERCELLS AND TORNADOES
  ESPECIALLY IN ERN IA...NW IL...SE MN AND SW WI WHERE A MODERATE RISK
  HAS BEEN PLACED. A FEW STRONG TORNADOES COULD OCCUR EITHER NEAR THE
  WARM FRONT IN THE AFTERNOON OR ALONG THE COLD FRONT AS THE LOW-LEVEL
  JET STRENGTHENS DURING THE EARLY EVENING.
 
  AT THIS POINT...THE MODELS APPEAR TO BE IN GOOD AGREEMENT CONCERNING
  THE TIMING AND STRENGTH OF THE SYSTEM. ALTHOUGH THIS IS THE
  CASE...AM EXPECTING THE UPPER-LEVEL TROUGH TO BE A BIT SLOWER INTO
  THE PLAINS SO HAVE NUDGED THE MODERATE RISK A BIT SWWD TO ACCOUNT
  FOR THIS.
 
  ...SRN AND CNTRL PLAINS...
  AN IMPRESSIVE UPPER-LEVEL TROUGH WILL MOVE INTO THE GREAT PLAINS
  SUNDAY. THUNDERSTORM DEVELOPMENT WILL BE PROBABLE AHEAD OF THE
  TROUGH ALONG A COLD FRONT FROM ERN KS SWD INTO ERN OK AND ECNTRL TX
  WHERE MODERATE INSTABILITY AND STRONG DEEP LAYER SHEAR IS FORECAST.
  DUE THE POTENTIAL FOR SUPERCELL DEVELOPMENT...AN ENHANCED THREAT FOR
  TORNADOES...LARGE HAIL AND WIND DAMAGE COULD OCCUR DURING THE EARLY
  EVENING FROM WCNTRL MO SWD INTO NW AR AND NE OK. THE THREAT SHOULD
  BE MORE ISOLATED IN SE OK AND ECNTRL TX BUT THE ENVIRONMENT SHOULD
  STILL SUPPORT HAIL AND WIND DAMAGE.
 
  ...UPPER OH VALLEY AND CNTRL APPALACHIAN MTNS...
  ISOLATED THUNDERSTORM DEVELOPMENT ALSO MAY OCCUR JUST TO THE EAST OF
  AN UPPER-LEVEL RIDGE IN THE UPPER OH VALLEY AND CNTRL APPALACHIAN
  MTNS. IN THIS REGION...MODELS FORECAST AN AXIS OF MODERATE
  INSTABILITY WITH ENOUGH DEEP LAYER SHEAR FOR A MARGINAL SEVERE
  THREAT MAINLY SUNDAY AFTERNOON.
 
  ..BROYLES.. 04/08/2011
52
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Setup for this Weekends Severe Weather Event - JAC, 4/6/2011, 7:26 am
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