Its all there: Sub-Trop Impulse, Lee Low, Negative Tilt
Posted by JAC on 5/9/2011, 6:03 am


DAY 3 CONVECTIVE OUTLOOK RESENT 1
  NWS STORM PREDICTION CENTER NORMAN OK
  0310 AM CDT MON MAY 09 2011
 
  VALID 111200Z - 121200Z
 
  ...THERE IS A SLGT RISK OF SVR TSTMS OVER A LARGE PORTION OF THE
  PLAINS AND UPPER MS VLY/MIDWEST...
 
  ...CNTRL/SRN PLAINS...
  AN ACTIVE WEATHER WEDNESDAY IS EXPECTED AS PRIMARY PORTION OF THE
  WRN STATES UPPER TROUGH BEGINS TO EJECT AS A NEGATIVE-TILT ENTITY
  INTO THE CNTRL/SRN PLAINS.  ACCOMPANYING LEE LOW WILL DEVELOP FROM
  SE CO INTO NCNTRL KS DURING THE AFTN AS THE DRYLINE MIXES EWD INTO
  CNTRL KS...WRN OK AND ERN EDWARDS PLATEAU IN TX.  60S SFC DEW POINTS
  AND 7-8.5 DEG C/KM MID-LEVEL LAPSE RATES WILL CONTRIBUTE TO VERY
  UNSTABLE CONDITIONS FROM CNTRL TX NWD TO THE NCNTRL KS/SCNTRL NEB
  BORDER.
 
  THERE ARE SOME MODELS THAT SUGGEST THAT A LEAD SUB-TROPICAL IMPULSE
  MAY AID IN THE INITIATION OF TSTMS ACROSS NCNTRL TX INTO SERN OK
  DURING THE EARLY-MID AFTN...BUT CONFIDENCE IS LOW AT THIS TIME AS IT
  IS UNCLEAR ON EXACTLY WHAT INITIATING BOUNDARY MAY PLAY A ROLE IN
  THIS INITIATION.  THIS POSSIBILITY WILL HAVE TO BE CONSIDERED AND
  WAS INCLUDED IN 15% SVR PROBS SINCE VERTICAL SHEAR/BUOYANCY WILL BE
  SUFFICIENT FOR ORGANIZED STORMS.  
 
  MEANWHILE...AS MID-LEVEL COOLING AND ASCENT TIED TO THE TROUGH
  SPREADS ACROSS THE HIGH PLAINS...COMBINATION OF HEATING AND ERODING
  CAP WILL LEAD TO TSTM INITIATION NEAR TRIPLE POINT OVER NWRN/CNTRL
  KS SWD ALONG THE DRYLINE INTO CNTRL TX BY MID-LATE AFTN.  SUPERCELLS
  WILL BE LIKELY WITH VERY LARGE HAIL...TORNADOES AND DMGG WINDS.
  STRONGER ASCENT WILL SPREAD ENE ACROSS KS/NEB AND TOWARD IA/NW MO
  WEDNESDAY NIGHT AND LIKELY SUPPORT ONE OR MORE CLUSTERS OF
  STRONG/SVR STORMS.  ADDITIONAL LONGER-LIVED TSTMS WILL LIKELY EXIST
  THROUGH MOST OF THE NIGHT ACROSS PARTS OF CNTRL/NRN TX WITH SIMILAR
  THREATS FOR HAIL AND HIGH WINDS.
 
  ...CORN BELT/UPPER MIDWEST...
  A BRANCH OF THE SWLY LLJ WILL CONTINUE TO ENHANCE LOW/MID-LEVEL WARM
  ADVECTION ALONG SRN PERIPHERY OF AN EJECTING IMPULSE OVER NWRN
  ONTARIO ON WEDNESDAY.  ELEVATED CLUSTERS OF STORMS MAY ALREADY BE
  ONGOING EARLY IN THE DAY OVER PARTS OF THE UPPER GREAT LAKES.  WRN
  PERIPHERY OF THESE STORMS MAY CONTINUE TO THRIVE ALONG EDGE OF THE
  CAP ACROSS PARTS OF THE UPPER MS VALLEY AND UPPER MIDWEST THROUGH
  THE DAY...BUT OVERALL CONFIDENCE IS LOW.  THERE WILL LIKELY BE AMPLE
  INSTABILITY IN PLACE TO SUPPORT ORGANIZED SEVERE STORMS...ALTHOUGH
  VERTICAL SHEAR MAY BE LACKING AS REGION BECOMES SANDWICHED BETWEEN
  THE DEPARTING ONTARIO IMPULSE AND UPPER LOW EJECTING INTO THE
  CNTRL/SRN HIGH PLAINS.
 
  ..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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