Sep 8, 2012 0100 UTC Day 1 Convective Outlook
Updated: Sat Sep 8 01:03:35 UTC 2012
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20120908 0100 UTC Day 1 Outlook Graphic
Probabilistic Tornado Graphic
20120908 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
20120908 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
20120908 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 080059
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0759 PM CDT FRI SEP 07 2012
   
   VALID 080100Z - 081200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS AR TO WRN PORTIONS
   NY/PA...
   
   ...SYNOPSIS...
   UPPER-AIR PATTERN OVER MOST OF CONUS IS INFLUENCED BY HUDSON BAY
   VORTEX AND WELL-DEFINED RIDGING OVER NRN ROCKIES AND INTERMOUNTAIN
   W.  BETWEEN THOSE FEATURES...STG AND POSITIVELY TILTED SHORTWAVE
   TROUGH WAS ANALYZED FROM LS/UPPER MI SWWD ACROSS IA TO SRN NEB THEN
   WWD OVER SRN WY.  NRN PORTION OF THIS TROUGH WILL BECOME LESS
   STRONGLY TILTED WITH TIME.  BY 12Z...500-MB TROUGH SHOULD EXTEND
   FROM LOWER MI TO SRN IL AND OZARKS...THEN ARCHING WSWWD-WNWWD OVER
   OK TO SERN CO/NERN NM REGION. 
   
   AT SFC...23Z ANALYSIS SHOWED SFC LOWS OVER SERN LOWER MI AND SWRN
   IL..CONNECTED BY COLD FRONT.  FRONT EXTENDED FROM IL LOW SWWD ACROSS
   S-CENTRAL MO....NWRN AR...S-CENTRAL OK...NW TX AND SERN NM.  COLD
   FRONT IS FCST TO CONTINUE SURGING SWD OVER SRN PLAINS AND SEWD
   ACROSS MID-LOWER MS VALLEY REGION...REACHING ERN OH...MIDDLE
   TN...NRN/WRN LA...UPPER TX COASTAL PLAIN AND NRN COAHUILA BY 12Z. 
   AS THIS OCCURS...SFC LOW SHOULD DEEPEN AND MOVE/REDEVELOP TO SERN
   ONT.  
   
   ...PORTIONS AR TO WRN PORTIONS NY/PA...
   BAND OF STG-SVR TSTMS OFFERING DAMAGING WINDS AND ISOLATED SVR HAIL
   HAS BECOME BETTER DEFINED FROM CENTRAL INDIANA TO SERN OK...PRECEDED
   BY WIDELY SCATTERED DISCRETE CONVECTION OF MULTICELLULAR/OCNL
   SUPERCELLULAR CHARACTER.  BELT OF SCTD POSTFRONTAL CONVECTION ALSO
   WAS EVIDENT OVER PORTIONS OK/NRN AR THAT STILL MAY POSE RISK OF
   ISOLATED STG-SVR GUSTS...DUE TO DOWNDRAFT ENHANCEMENT OF STG
   POSTFRONTAL GRADIENT FLOW. FRONTAL/PREFRONTAL CONVECTION WILL
   CONTINUE TO POSE MAIN WIND-DAMAGE HAZARD THROUGH REMAINDER
   PERIOD...WITH CONDITIONAL TORNADO POTENTIAL MAINLY ACCOMPANYING
   SUITABLY STRUCTURED QLCS MESOVORTICES AND/OR INTENSE BOW
   CIRCULATIONS.  WIND THREAT WILL BE ENHANCED INVOF LOCALIZED LEWP/BOW
   FEATURES THAT HELP TO BRING HIGH-MOMENTUM FLOW TO SFC.  REF
   REMAINDER SPC WWS 630...631...632...633 AND RELATED MESOSCALE
   DISCUSSIONS FOR LATEST NEAR-TERM GUIDANCE ON SVR THREAT. 
   
   OVERNIGHT PROBABILITIES SUPPORTING CATEGORICAL SVR THREAT ARE
   EXPANDED SOMEWHAT SEWD ACROSS CORRIDOR FROM AR-MS TO WV TO ACCOUNT
   FOR TIMING OF THIS ACTIVITY AND POTENTIAL FOR AT LEAST MRGLLY
   FAVORABLE BUOYANCY/SHEAR OVERLAP OVER PORTIONS MID-SOUTH AND CENTRAL
   APPALACHIANS BEFORE 12Z.  SUBSTANTIALLY COUNTERBALANCING INFLUENCES
   LEND CONSIDERABLE UNCERTAINTY AS TO HOW FAR NE AND HOW FAR INTO
   PRE-DAWN HOURS ORGANIZED SVR WIND THREAT WILL PERSIST WITH PRIMARY
   BAND OF CONVECTION.  ON ONE HAND...STG LOW-LEVEL WAA AND MOISTURE
   TRANSPORT WILL OCCUR OVER PREFRONTAL OH/TN VALLEY REGIONS...WHILE
   FRONTOGENETIC FORCING STRENGTHENS AHEAD OF FAVORABLE EVOLVING
   MID-UPPER WAVE.  HOWEVER...DIABATIC SFC COOLING WILL REDUCE MLCAPE
   AND INCREASE MLCINH WITH TIME.  DEEP-LAYER SHEAR AND LARGE-SCALE
   SUPPORT ALSO WILL DIMINISH WITH SWD EXTENT.
   
   ..EDWARDS.. 09/08/2012
   
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   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0600Z