Moving into a weaker cap
Posted by JAC on 8/4/2009, 9:06 am



MESOSCALE DISCUSSION 1769
  NWS STORM PREDICTION CENTER NORMAN OK
  0711 AM CDT TUE AUG 04 2009
 
  AREAS AFFECTED...NERN MO...SERN IA...WRN IL
 
  CONCERNING...SEVERE THUNDERSTORM WATCH 654...
 
  VALID 041211Z - 041345Z
 
  THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 654
  CONTINUES.
 
  PRIMARY SEVERE WEATHER THREAT IS EXPECTED ACROSS ERN PORTIONS OF WW
  654 FROM SERN IA THROUGH WRN IL THROUGH 14Z. STORMS HAVE APPROACHED
  THE ERN EDGE OF WW AND ANOTHER WW IS BEING CONSIDERED FARTHER EAST
  INTO CNTRL IL.
 
  A CONVECTIVE OUTFLOW BOUNDARY EXTENDS FROM SERN IA...EXTREME WRN IL
  THEN SWWD AND WWD THROUGH NRN MO. STORMS HAVE STRUGGLED TO DEVELOP
  ALONG SRN FLANKS OF THE OUTFLOW BOUNDARY...MOST LIKELY DUE TO A MORE
  STRONGLY CAPPED ENVIRONMENT OVER CNTRL MO. HOWEVER...RECENT RADAR
  TRENDS HAVE INDICATED STORMS HAVE BEGUN TO FORWARD PROPAGATE ALONG
  PORTION OF OUTFLOW BOUNDARY FROM SERN IA THROUGH WRN IL. POTENTIAL
  EXISTS FOR STORMS TO DEVELOPING EWD THROUGH CNTRL IL THIS MORNING
  ALONG INSTABILITY GRADIENT WHERE THE 12Z LINCOLN RAOB INDICATES A
  WEAK CAP...STRONG INSTABILITY AND STEEP LAPSE RATES IN THE 850-500
  MB LAYER. THE STORMS ARE EMBEDDED WITHIN UNIDIRECTIONAL 30-35 KT
  BULK SHEAR. DAMAGING WIND AND LARGE HAIL WILL REMAIN THE PRIMARY
  THREATS.
 
  ..DIAL.. 08/04/2009
20
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Bowing MCS moving thru Central IL - JAC, 8/4/2009, 9:04 am
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