Good chance for Derecho's today. Textbook Hodos
Posted by JAC on 10/29/2009, 7:01 am



DAY 1 CONVECTIVE OUTLOOK  
  NWS STORM PREDICTION CENTER NORMAN OK
  1256 AM CDT THU OCT 29 2009
 
  VALID 291200Z - 301200Z
 
  ...THERE IS A SLGT RISK OF SVR TSTMS FROM PARTS OF THE SRN AND CNTRL
  PLAINS INTO THE LOWER MS VALLEY...
 
  ...SYNOPSIS...
 
  POSITIVE TILT UPPER TROUGH OVER THE SWRN STATES WILL ADVANCE SLOWLY
  EAST THIS PERIOD WHILE A SERIES OF IMPULSES MOVE THROUGH THIS
  FEATURE. LEAD IMPULSE CURRENTLY OVER THE SRN AND CNTRL HIGH PLAINS
  WILL LIFT NWD THROUGH THE NRN PLAINS EARLY THURSDAY. A STRONGER
  UPPER JET NOW ROUNDING THE BASE OF THE TROUGH WILL EJECT NEWD
  THROUGH THE SRN PLAINS THIS AFTERNOON...REACHING THE CNTRL PLAINS BY
  EARLY EVENING. AT THE SURFACE A WARM FRONT WILL LIFT NWD ACROSS NERN
  TX...SERN OK AND THE LOWER MS VALLEY. A SURFACE LOW WILL DEVELOP
  NEWD ALONG THE FRONT IN ASSOCIATION WITH EJECTING UPPER JET. THIS
  FEATURE WILL REACH THE UPPER MS VALLEY LATE THURSDAY NIGHT. THE
  TRAILING COLD FRONT WILL ADVANCE SLOWLY EWD THROUGH THE CNTRL AND
  SRN PLAINS TODAY AND MID-LOWER MS VALLEY OVERNIGHT.
 
  ...SRN PLAINS THROUGH SERN KS...SWRN MO AND LOWER MS VALLEY...
 
  RICH GULF MOISTURE WITH LOW 60S DEWPOINTS AS FAR NORTH AS ERN OK AND
  LOW 70S ACROSS ERN TX AND THE LOWER MS VALLEY WILL ADVECT NWD IN
  WAKE OF RETREATING WARM FRONT ALONG STRONG LOW LEVEL JET. MODEST MID
  LEVEL LAPSE RATES AND AREAS OF CLOUDS WILL LIKELY LIMIT MLCAPE TO
  AOB 1500 J/KG ACROSS MUCH OF THE WARM SECTOR...BUT MLCAPE COULD
  APPROACH 2000 J/KG WHERE LOW CLOUDS CAN MIX OUT.
 
  SCATTERED THUNDERSTORMS...MOST OF WHICH SHOULD BE AT LEAST SLIGHTLY
  ELEVATED...MAY BE ONGOING EARLY THURSDAY MAINLY FROM NERN TX...ERN
  OK INTO THE LOWER MS VALLEY WITHIN ZONE OF STRONGER ISENTROPIC LIFT
  NORTH OF RETREATING WARM FRONT. UPPER FLOW WILL REMAIN MERIDIONAL
  EAST OF UPPER TROUGH AND MAY RESULT IN AT LEAST SLIGHT WARMING IN
  THE 850-500 MB LAYER ACROSS WARM SECTOR. THIS AND TENDENCY FOR
  DEEPER FORCING ASSOCIATED WITH EJECTING UPPER JET TO REMAIN POST
  FRONTAL RAISES CONCERNS THAT THE THERMODYNAMIC ENVIRONMENT COULD
  POTENTIALLY LIMIT THE ROBUSTNESS AND EXTENT OF SURFACE BASED
  THUNDERSTORMS IN WARM SECTOR. HOWEVER...VERTICAL SHEAR AND 0-1 KM
  HODOGRAPHS WILL REMAIN SUFFICIENT FOR A THREAT OF SUPERCELLS AND
  ISOLATED TORNADOES WITH ANY SURFACE BASED STORMS THAT DEVELOP.
 
  OTHER STORMS WILL LIKELY CONTINUE WITHIN CORRIDOR OF DEEP ASCENT
  ALONG BAROCLINIC ZONE AS IT ADVANCES EAST THROUGH TX...OK AND ERN KS
  DURING THE DAY. THE NATURE OF THE FORCING AND MERIDIONAL UPPER FLOW
  WILL PROMOTE PRIMARILY LINEAR STRUCTURES. HOWEVER...STORMS WILL
  REMAIN WITHIN AN ENVIRONMENT CHARACTERIZED BY 50+ KT BULK SHEAR AND
  SUFFICIENTLY LARGE LOW LEVEL HODOGRAPHS FOR EMBEDDED SUPERCELLS AND
  BOWING SEGMENTS. DAMAGING WIND WILL BE THE MAIN THREAT WITH THIS
  ACTIVITY...BUT ISOLATED TORNADOES WILL ALSO BE POSSIBLE. THREAT FOR
  ISOLATED DAMAGING WIND MAY EXTEND AS FAR NORTH AS SERN KS AND SRN
  MO...BUT NWD EXTENT OF THREAT WILL BE LIMITED BY WEAK INSTABILITY.
 
  ..DIAL/GARNER.. 10/29/2009









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Possible Severe System for MS-Valley/Midwest around the Weekend - JAC, 10/26/2009, 3:53 pm
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