Sep 6, 2012 0600 UTC Day 1 Convective Outlook
Updated: Thu Sep 6 05:42:27 UTC 2012
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20120906 1200 UTC Day 1 Outlook Graphic
Probabilistic Tornado Graphic
20120906 1200 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
20120906 1200 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
20120906 1200 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 060539
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1239 AM CDT THU SEP 06 2012
   
   VALID 061200Z - 071200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS CENTRAL/SRN PLAINS...
   
   ...SYNOPSIS...
   COMPLEX UPPER-AIR PATTERN WILL PREVAIL OVER AND NEAR CONUS THROUGH
   PERIOD.  STG SHORTWAVE TROUGH INITIALLY OVER NRN ONT SHOULD MOVE
   NEWD AND EVOLVE INTO CLOSED LOW...WHILE TRAILING CYCLONE NOW OVER MB
   MOVES SEWD AND DEAMPLIFIES TO OPEN-WAVE TROUGH.  NET EFFECT WILL BE
   TO SHIFT CANADIAN VORTEX EWD TO JAMES BAY THROUGH PERIOD. 
   MEANWHILE...STG SHORTWAVE TROUGH -- NOW EVIDENT IN MOISTURE CHANNEL
   IMAGERY OVER SERN BC -- IS FCST TO TRANSLATE ESEWD OVER
   MT/DAKOTAS...PHASING WITH REMAINS OF PERTURBATION NOW OVER NERN MB. 
   NET RESULT SHOULD BE POSITIVELY TILTED TROUGH FROM NWRN ONT/WRN LS
   AREA SWWD ACROSS CENTRAL/SRN SD BY 7/12Z.  MEANWHILE...THREE CUT-OFF
   SYSTEMS ARE EVIDENT ATTM...
   1. OFFSHORE E COAST OF FL...FCST TO MOVE EWD UNDER INFLUENCE OF SRN
   FRINGE OF NRN-STREAM TROUGH THAT WILL MOVE OFF MID-ATLC COAST AROUND
   6/18Z.
   2. S OF MS RIVER MOUTH...AND FCST TO MOVE SWD OR SWWD OVER OPEN
   GULF.  INFLUENCE OF THIS AND ATLC PERTURBATION ON INLAND CONVECTIVE
   PROCESSES EACH WILL LESSEN WITH TIME THIS PERIOD.  FOR DISCUSSION OF
   POTENTIAL TROPICAL DEVELOPMENT WITH THIS SYSTEM...REF NHC TROPICAL
   OUTLOOKS UNDER WMO HEADER ABNT20 KNHC.
   3. BROAD/WEAK CLOSED CYCLONE NOW OFFSHORE NRN CA...AND PROGGED TO
   DRIFT NWD...E OF WHICH DIFLUENT MID-UPPER FLOW...HEATING OF HIGHER
   TERRAIN AND AT LEAST MRGL MOISTURE WILL SUPPORT GEN TSTM POTENTIAL
   OVER PORTIONS INLAND NRN CA/ORE.
   
   AT SFC...NRN-PLAINS FRONTOGENESIS AND SWD MOTION OF BAROCLINICITY IS
   FCST THROUGH 7/00Z...AS HEIGHTS ALOFT FALL IN ADVANCE OF NRN-ROCKIES
   SHORTWAVE TROUGH.  RESULT SHOULD BE SFC LOW OVER NERN NEB/SERN SD
   AREA BY 7/00Z...WITH COLD FRONT SWWD OVER SWRN/W-CENTRAL NEB TO SERN
   WY...AND WARM FRONT SEWD ACROSS WRN IA.  COLD FRONT SHOULD CONTINUE
   ITS SEWD PROGRESS OVER CENTRAL PLAINS...REACHING SRN IA...NWRN
   MO...AND CENTRAL/SWRN KS BY 7/12Z.  PREFRONTAL
   CONFLUENCE/CONVERGENCE ZONE IS EXPECTED TO DEVELOP FROM CENTRAL NEB
   SWWD ACROSS WRN KS TO EXTREME SERN CO AND WRN OK PANHANDLE BY
   7/00Z...NEARLY COLLOCATED WITH SHARPENING DRYLINE.  THIS BOUNDARY
   WILL BE OVERTAKEN BY FRONT OVERNIGHT.
   
   ...CENTRAL/SRN PLAINS...
   STG DIABATIC HEATING AND LIFT INVOF DRYLINE/CONFLUENCE ZONE SHOULD
   CONTRIBUTE TO WEAKENING MLCINH AND DEVELOPMENT OF TSTMS DURING LATE
   AFTERNOON.  SCATTERED TSTMS SHOULD FORM IN SW-NE BAND FROM TX/OK
   PANHANDLES NEWD AT LEAST AS FAR AS CENTRAL PORTIONS KS/NEB
   BORDER...AND PROBABLY FARTHER N INTO SRN/CENTRAL NEB AS MOIST
   ADVECTION OCCURS EQUATORWARD OF SFC LOW.  DAMAGING GUSTS AND LARGE
   HAIL WILL BE POSSIBLE.  WEAK LOW-LEVEL WINDS WILL LIMIT ORGANIZED
   TORNADO THREAT...THOUGH DEEP SHEAR MAY BE SUFFICIENT TO SUPPORT SOME
   SUPERCELL TENDENCIES WITH ANY RELATIVELY DISCRETE CONVECTION IN THAT
   CORRIDOR.
   
   BY LATE AFTERNOON...MOIST-SECTOR AIR MASS SHOULD BE HOTTER AND MORE
   WELL-MIXED WITH SWD EXTENT ACROSS KS...OK AND TX PANHANDLE.  THIS
   WILL HAVE TWO PRIMARY EFFECTS...
   1. DIMINISH CAPE AND RAISE LCL WITH SWD EXTENT...THOUGH BUOYANCY
   STILL SHOULD BE FAVORABLE OVER SVR OUTLOOK AREA...AND
   2. AID POTENTIAL FOR DAMAGING DOWNDRAFT ACCELERATIONS THROUGH DEEPER
   SUBCLOUD LAYERS.
   ACTIVITY MAY ORGANIZE INTO MCS WITH SHORT-LIVED/COLD-POOL DRIVEN SVR
   WIND THREAT DURING EVENING...BEFORE MOVING EWD AND WEAKENING.
   
   ...INTERIOR MID-ATLC TO MID-SOUTH/OZARKS REGION...
   WIDELY SCATTERED TO SCATTERED TSTMS ARE EXPECTED TO DEVELOP ALONG
   AND SE OF EWD EXTENSION OF IA/MO FRONTAL ZONE THIS
   AFTERNOON...BENEATH STRONGLY DIFLUENT UPPER-LEVEL FLOW AND WEAK
   MLCINH.  LOW-MIDDLE LEVEL FLOW FROM NY-OH WILL BE GENERALLY
   UNIDIRECTIONAL...WITH BULK SHEAR LIMITED BY LACK OF MORE ROBUST
   SPEEDS.  HOWEVER...STG UPPER/ANVIL-LEVEL FLOW FROM TN NEWD SHOULD
   AID IN CONVECTIVE VENTILATION ALOFT AND MULTICELLULAR STORM
   ORGANIZATION ON MESOBETA AND SMALLER SCALES.  SFC DEW POINTS
   MID-UPPER 60S F IN MOST AREAS SHOULD SUPPORT PEAK MLCAPE IN
   1000-2000 J/KG RANGE.
   
   ..EDWARDS/LEITMAN.. 09/06/2012
   
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