Aug 21, 2011 0100 UTC Day 1 Convective Outlook
Updated: Sun Aug 21 01:02:12 UTC 2011
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20110821 0100 UTC Day 1 Outlook Graphic
Probabilistic Tornado Graphic
20110821 0100 UTC Day 1 Tornado Probabilities Graphic
Probability of a tornado within 25 miles of a point.
Hatched Area: 10% or greater probability of EF2 - EF5 tornadoes within 25 miles of a point.
Probabilistic Damaging Wind Graphic
20110821 0100 UTC Day 1 Damaging Wind Probabilities Graphic
Probability of damaging thunderstorm winds or wind gusts of 50 knots or higher within 25 miles of a point.
Hatched Area: 10% of greater probability of wind gusts 65 knots or greater within 25 miles of a point.
Probabilistic Large Hail Graphic
20110821 0100 UTC Day 1 Large Hail Probabilities Graphic
Probability of hail 1" or larger within 25 miles of a point.
Hatched Area: 10% or greater probability of hail 2" or larger within 25 miles of a point.
   SPC AC 210058
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0758 PM CDT SAT AUG 20 2011
   
   VALID 210100Z - 211200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF SRN MO AND NRN
   AR...
   
   ...SYNOPSIS...
   A BROAD CYCLONIC FLOW REGIME/STRONGER FLOW ALOFT WILL CONTINUE TO
   EVOLVE SWD INTO THE GREAT LAKES...WITH AMPLIFICATION SEWD TO THE OH
   VALLEY THIS FORECAST PERIOD.  MEANWHILE...A MID MS VALLEY/OZARKS
   SHORTWAVE TROUGH AND ATTENDANT BAND OF 40-50 KT WLY MIDLEVEL WINDS
   WILL ADVANCE ESEWD INTO THE OH/TN VALLEYS TONIGHT.  AT THE
   SURFACE...A COLD FRONT ATTENDANT TO THE LARGE SCALE TROUGH EXTENDED
   FROM SWRN ONTARIO TO NRN IND...ERN IL THROUGH SWRN MO...AND WSWWD
   THROUGH CENTRAL OK TO THE TX PANHANDLE LATE THIS AFTERNOON.  BY 12Z
   SUNDAY...THIS BOUNDARY SHOULD EXTEND FROM THE LOWER GREAT LAKES
   THROUGH ERN OH...KY TO NRN AR AND WWD INTO OK.
   
   ...SRN MO/AR TO LOWER TN VALLEY/PARTS OF MID SOUTH...
   ONGOING CLUSTER OF STRONG TO SEVERE STORMS HAS EVOLVED OVER FAR SRN
   MO INTO NWRN AR INVOF OF THE NRN EXTENT OF A WWD MOVING CONVECTIVE
   OUTFLOW BOUNDARY AND ITS INTERSECTION WITH A SSEWD ADVANCING COLD
   FRONT TOWARD NRN AR AND ERN OK.  IN THE SHORT TERM...STRONGEST
   INSTABILITY RESIDES ALONG THE SRN-WRN FLANKS OF THE CLUSTER/MCS WITH
   20 KT OF SSWLY LOW LEVEL FLOW INTO THIS SYSTEM SUPPORTING ADDITIONAL
   DEVELOPMENT IN THE SHORT TERM /THROUGH 02Z/.  FOR ADDITIONAL
   DETAILS...REFER TO SPC MESOSCALE DISCUSSION #2029.  AFTER
   02Z...MODELS SUGGEST A WLY LLJ...THOUGH MODEST IN SPEED /20-30 KT/
   ACROSS NRN AR...AND THE ESEWD TRACK OF THE MID MS VALLEY/OZARKS
   TROUGH SUGGEST SOME POTENTIAL FOR STRONGER...SOME SEVERE STORMS TO
   SPREAD E TOWARD SERN MO/NERN AR.  FOR THESE REASONS...THE SLIGHT
   RISK AREA HAS BEEN EXPANDED EWD WITH THIS OUTLOOK ISSUANCE.
   
   ...ERN IL/IND/WRN OH...
   MIDLEVEL ASCENT ATTENDANT TO THE APPROACH OF THE MID MS VALLEY
   SHORTWAVE TROUGH SHOULD PROVE SUFFICIENT IN SUPPORTING A FEW
   ADDITIONAL MORE ROBUST UPDRAFTS/STRONGER STORMS ACROSS ERN IL TO
   WRN/SRN IND THROUGH THE EVENING/EARLY OVERNIGHT PERIOD.  SHORT TERM
   MODELS SUGGEST A CONVECTIVE POTENTIAL WILL OCCUR THIS FORECAST
   PERIOD INTO THE LOWER OH VALLEY.  HOWEVER...WEAK LOW LEVEL
   CONVERGENCE AND WEAK LOW LEVEL WAA INDICATE THAT THE LIKELIHOOD FOR
   STRONGER STORM DEVELOPMENT AND WEAKENING DEEP LAYER SHEAR WILL
   PRECLUDE AN ORGANIZED SEVERE THREAT.
   
   ..PETERS.. 08/21/2011
   
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   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0600Z