SPC puts Moderate Risk for Wednesday
Posted by JAC on 5/10/2011, 5:15 am



DAY 2 CONVECTIVE OUTLOOK  
  NWS STORM PREDICTION CENTER NORMAN OK
  1257 AM CDT MON MAY 09 2011
 
  VALID 101200Z - 111200Z
 
  ...THERE IS A SLGT RISK OF SVR TSTMS FROM THE OH VLY TO THE SE
  ATLANTIC COAST...
 
  ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PORTIONS OF THE NRN
  PLAINS/UPPER MS VLY...
 
  ...THERE IS A SLGT RISK OF SVR TSTMS IN THE SRN PLAINS...
 
  ...MIDWEST TO THE SE ATLANTIC COAST...
  MODELS HAVE BEEN MAINTAINING A CONSISTENT MESSAGE IN MAINTAINING A
  RIDGE-TOPPING... CONVECTIVELY-INDUCED IMPULSE /CURRENT MCS OVER ERN
  DAKOTAS/ SEWD INTO THE OH VLY BY 12Z TUE AND INTO THE SRN
  APPALACHIANS AND SERN COASTAL STATES DURING TUESDAY PEAK HEATING.
  THIS WILL AUGMENT AN ALREADY ENHANCED BELT OF WNW FLOW ALOFT /H5 40+
  KTS/.  TSTMS WILL READILY FORM ALONG FRINGE OF THE EML/FRONT AS
  HEATING AND LARGE-SCALE SUPPORT SPREADS SEWD TUESDAY AFTN WITH
  THREATS FOR ORGANIZED MULTICELL STORMS AND ISOLD SUPERCELLS.  DMGG
  WIND GUSTS...LARGE HAIL AND POSSIBLY A COUPLE TORNADOES CAN BE
  EXPECTED...PARTICULARLY FROM UPSTATE SC/WRN NC TO THE COASTAL
  PLAINS.
 
  ...NRN PLAINS/UPPER MS VLY...
  STRONG MID-LEVEL WAVE...CURRENTLY ROUNDING BASE OF THE WRN STATES
  UPR TROUGH...WILL TRANSLATE INTO THE NRN PLAINS BY TUESDAY AFTN.
  ATTENDANT SFC LOW WILL TRAVEL NWD FROM NCNTRL SD AT 12Z TUE TO NERN
  ND BY EVENING AND INTO SRN MANITOBA OVERNIGHT.  DRYLINE/FRONT WILL
  ADVANCE NEWD THROUGH ERN ND AND CNTRL/NRN MN TUESDAY AFTN AND MAY BE
  FOCUS FOR A FEW SEVERE TSTMS.
 
  WEDGE OF UPR 50S-MID 60S DEW POINTS WILL ADVECT WNW AHEAD OF THE
  FRONT TO THE SFC LOW AND CONTRIBUTE TO MLCAPES OF 1500+ J/KG.  VERY
  STRONG EML SHOULD DECREASE PROBABILITIES FOR SFC-BASED STORMS WITH
  SWD EXTENT ALONG THE SURGING FRONT...BUT AS LARGER-SCALE HEIGHT
  FALLS/COOLING TEMPERATURES ALOFT GRAZE ERN ND AND CNTRL/NRN
  MN...TSTMS MAY FORM.  SUPERCELLULAR WIND PROFILES WILL EXIST WITH
  THREATS FOR LARGE HAIL AND POSSIBLY TORNADOES.  LOW-CONFIDENCE IN
  EXTENT OF CONVECTIVE INITIATION WILL PRECLUDE HIGHER PROBABILITIES
  AT THIS TIME.  WHAT ACTIVITY DOES FORM WILL BEGIN TO ENCOUNTER
  COOLER ELY FLOW OFF LAKE SUPERIOR OVER NERN MN WITH TIME TUESDAY
  EVENING AND DECREASE TORNADO THREATS.  BUT...SUFFICIENT ELEVATED
  INSTABILITY WILL EXIST FOR AT LEAST ISOLD LARGE HAIL AS STORMS
  DEVELOP ESE TOWARD PARTS OF WI AND UPPER MI TUESDAY NIGHT.
 
  ...ERN PARTS OF CNTRL/SRN PLAINS...
  REGION WILL REMAIN IN SUSTAINED SLY LOW-LEVEL FLOW THAT WILL
  MAINTAIN RELATIVELY RICH BOUNDARY LAYER MOISTURE /SFC DEW POINTS IN
  THE 60S/ THROUGH TUESDAY.  THIS MOISTURE WILL BE TOPPED BY A STRONG
  EML THAT WILL RESULT IN A STRONG CAP...BUT POTENTIALLY VERY STRONG
  INSTABILITY GIVEN 8+ DEG C/KM H5-H7 LAPSE RATES.
 
  SECONDARY MID-LEVEL WAVE...EXPECTED TO BEGIN AN ENE TREK TO THE SRN
  ROCKIES BY TUESDAY AFTN...WILL RESULT IN WEAKLY DIFLUENT UPR FLOW
  REGIME ACROSS THE DRYLINE DURING THE AFTN/EVE.  ALTHOUGH STORM
  INITIATION CANNOT BE RULED OUT FROM NRN OK INTO CNTRL/ERN
  KS...HIGHER PROBABILITIES WILL EXIST FROM CNTRL/SWRN OK INTO THE ERN
  EDWARDS PLATEAU OF TX WHERE HOTTEST BOUNDARY LAYER TEMPERATURES
  SHOULD EXIST.  WIND PROFILES CONSISTING OF VERTICAL SHEAR OF 45-50
  KTS...AND THE MAGNITUDE OF LAPSE RATES WILL YIELD SUPERCELLS WITH
  LARGE HAIL AND PERHAPS ISOLD TORNADOES/DMGG WIND GUSTS DURING THE
  EVENING.  ACTIVITY MAY PERSIST INTO LATE EVENING ACROSS ERN OK TO
  CNTRL TX WITH AT LEAST ISOLD LARGE HAIL.
 
  MEANWHILE...WRN FRINGES OF EVENING MOISTURE SURGE MAY IGNITE INTO
  TSTMS VERY LATE IN THE PERIOD AS THE UPPER TROUGH EDGES TO THE SRN
  HIGH PLAINS.  THESE STORMS MAY PRODUCE ISOLD LARGE HAIL FROM THE TX
  S PLAINS INTO THE TRANS-PECOS REGION OF SW TX.
 
  ..RACY.. 05/09/2011
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Another Possible Severe Event Around May 10 thru 12 - JAC, 5/3/2011, 7:13 am
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