Sep 7, 2012 0100 UTC Day 1 Convective Outlook
Updated: Fri Sep 7 01:04:32 UTC 2012
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20120907 0100 UTC Day 1 Outlook Graphic
Probabilistic Tornado Graphic
20120907 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
20120907 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
20120907 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 070100
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0800 PM CDT THU SEP 06 2012
   
   VALID 070100Z - 071200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS CENTRAL/SRN
   PLAINS...IA TO NWRN IL...
   
   ...SYNOPSIS...
   MID-UPPER LEVEL PATTERN REMAINS DOMINATED LARGELY BY HUDSON BAY-AREA
   VORTEX...ZONAL TO GENTLY CYCLONIC FLOW TO ITS S ACROSS NRN HALF OF
   CONUS...AND CUT-OFF LOWS OFF ERN FL AND OFF NRN CA.  STG SHORTWAVE
   TROUGH -- NOW EVIDENT IN MOISTURE CHANNEL IMAGERY OVER MB/ONT BORDER
   REGION SWWD OVER MT -- IS FCST TO MOVE SEWD THROUGH REMAINDER
   PERIOD.  BY 12Z...TROUGH SHOULD EXTEND FROM ONT N OF LS...ACROSS NRN
   MN...ERN ND...WRN SD...AND NRN WY.  BETWEEN THAT TROUGH AND ATLC
   PERTURBATION OFFSHORE FL...STRONGLY DIFLUENT FLOW WILL COVER AREAS
   FROM OH VALLEY SWD ACROSS MUCH OF DIXIE.
   
   AT SFC...WEAK LOWS WERE ANALYZED AT 23Z OVER ERN NY AND SERN LOWER
   MI...CONNECTED BY WEAK COLD FRONT THAT WAS DRAWN ACROSS ERN PORTIONS
   OF WRN NY...NWRN PA...AND NERN OH.  COLD FRONT EXTENDED SWWD FROM
   SERN MI ACROSS NWRN OH...W-CENTRAL INDIANA...AND S-CENTRAL
   IL...BECOMING QUASISTATIONARY ACROSS NRN MO AND WARM FRONT OVER
   EXTREME ERN NEB...INTO ANOTHER SFC LOW BETWEEN FSD-ONL. FRONT THEN
   EXTENDED SWWD OVER CENTRAL NEB AND WWD OVER NEB PANHANDLE.  LATTER
   LOW SHOULD MOVE SEWD ACROSS IA AND WEAKEN THROUGH REMAINDER
   PERIOD...WHILE PLAINS SEGMENT OF COLD FRONT PROCEEDS SEWD ACROSS NEB
   TO NERN/N-CENTRAL/SWRN KS.  SECONDARY SFC CYCLONE SHOULD DEVELOP
   WHERE THAT FRONT INTERSECTS LEE TROUGH OVER SERN CO/SWRN KS. 
   COMBINED SFC TROUGH/DRYLINE/CONFLUENCE ZONE WAS ANALYZED FROM SERN
   NM NNEWD ACROSS WRN PANHANDLE OF OK...W-CENTRAL/NW KS AND S-CENTRAL
   NEB TO SFC LOW.  COLD FRONT SHOULD OVERTAKE KS/NEB PORTION OF
   DRYLINE/TROUGH FROM N-S THROUGH 12Z.  MEANWHILE...MUCH OF FRONTAL
   ZONE FROM IL-NY SHOULD BECOME QUASISTATIONARY.
   
   ...CENTRAL/SRN PLAINS...IA TO NWRN IL...
   BKN BAND OF STG-SVR TSTMS...INCLUDING A FEW ORGANIZED MULTICELL/OCNL
   SUPERCELL CONVECTIVE MODES...CONTINUE TO MOVE EWD AND SEWD AWAY FROM
   GENESIS REGION NEAR TROUGH/DRYLINE.  FAVORABLE DEEP-LAYER SHEAR WILL
   PERSIST...THOUGH STABILIZATION OF NEAR-SFC LAYER WILL REDUCE CURRENT
   700-1300 J/KG MLCAPE WITH TIME.  REF SPC WW 627 AND RELATED
   MESOSCALE DISCUSSIONS FOR NEAR-TERM INSIGHT.  ADDITIONAL DEVELOPMENT
   IS POSSIBLE INVOF ERN NEB/WRN IA OVERNIGHT...AS
   1. LOW-LEVEL WAA AND MOISTURE TRANSPORT INCREASE CURRENTLY MEAGER
   LOW-LEVEL THETAE EVIDENT IN OAX RAOB...AND
   2. THAT AIR IS LIFTED ISENTROPICALLY TO LFC NEAR AND NE OF WARM
   FRONT...LEADING TO ENVIRONMENT CHARACTERIZED BY ELEVATED MUCAPE
   AROUND 500 J/KG AND EFFECTIVE SHEAR MAGNITUDES 45-55 KT.
   MAIN CONCERN WITH THAT ACTIVITY WILL BE LARGE HAIL...THOUGH ISOLATED
   STG/DAMAGING GUSTS MAY PENETRATE TO SFC.
   
   ...OZARKS TO WRN PORTIONS KY/TN...
   PRIMARY CONVECTIVE AREA CONSISTS OF BOW ECHO OVER WRN PORTIONS TN/KY
   THAT HAS UNDERGONE PRONOUNCED WEAKENING TREND DURING PAST 1-2 HOURS
   IN REFLECTIVITY...IR IMAGERY AND LTG DATA.  ALTHOUGH SVR THREAT HAS
   DIMINISHED CONSIDERABLY...WITH GUST FRONT SURGING WELL AHEAD OF THIS
   CONVECTION.  ADDITIONAL TSTMS OVER NRN AR/SRN MO OZARKS MAY POSE
   RISK OF ISOLATED DAMAGING DOWNDRAFTS AND MRGLLY SVR HAIL FOR ANOTHER
   FEW HOURS BEFORE AIR MASS BECOMES TOO STABLE TO SUPPORT SVR THREAT. 
   FOR ADDITIONAL DETAILS REF SPC MESOSCALE DISCUSSION 1906.
   
   ...INLAND MID-ATLC...NRN APPALACHIANS...
   LOOSELY ORGANIZED MULTICELLULAR COMPLEX OF TSTMS PERSISTS ATTM
   ACROSS NRN PORTIONS PA...WITH MORE ISOLATED ACTIVITY FARTHER NW OVER
   ERN NY AND VT/MA BORDER REGION.  ISOLATED DAMAGING GUSTS OR SVR HAIL
   REMAIN POSSIBLE FOR ANOTHER COUPLE HOURS. HOWEVER...SVR POTENTIAL
   SHOULD CONTINUE TO DIMINISH THROUGH REMAINDER EVENING AS DIABATIC
   SFC COOLING RENDERS INFLOW-LAYER PARCELS PROGRESSIVELY MORE STABLE
   WITH TIME.
   
   ..EDWARDS.. 09/07/2012
   
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