Categorical Graphic
Probabilistic Tornado 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
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
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 061257
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0757 AM CDT THU SEP 06 2012
   
   VALID 061300Z - 071200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE GREAT PLAINS TO
   UPPER MIDWEST...
   
   ...SYNOPSIS...
   AN EXTENSIVE BELT OF BROADLY CYCLONIC MID/UPPER LEVEL FLOW ACROSS
   THE NRN 1/3RD OF THE CONUS WILL AMPLIFY THIS PERIOD AS SHORT WAVE
   TROUGHS ROTATES THROUGH THE LARGER SCALE DEEP-LAYER CYCLONE ACROSS
   MUCH OF SRN/CNTRL CANADA. IN ADDITION TO A WELL-DEFINED SHORT WAVE
   TROUGH ON WATER VAPOR IMAGERY DIGGING SWD TOWARD THE NRN ROCKIES
   FROM BC/AB ATTM...OTHER DISTURBANCES ARE EMANATING FROM A LARGE
   PACIFIC TROUGH OFF OF NRN CA. THESE IMPULSES WILL ENTER A ZONE OF
   FASTER CONFLUENT MID LEVEL FLOW ACROSS THE GREAT BASIN AND NRN HIGH
   PLAINS BEFORE MERGING WITH THE AMPLIFYING NRN STREAM SHORTWAVE
   TROUGH AND PRODUCING A LARGE AREA OF MODEST 500MB HEIGHT FALLS FROM
   THE CNTRL PLAINS TO UPPER MS VALLEY AND WRN GREAT LAKES BY FRIDAY
   MORNING. THE END RESULT WILL BE A POSITIVE TILT TROUGH ORIGINATING
   FROM A CLOSED LOW NORTH OF JAMES BAY AND EXTENDING SWWD TO THE CNTRL
   PLAINS. SOUTH OF THIS TROUGH...THE SUBTROPICAL RIDGE WILL HOLD FIRM
   FROM THE SOUTHWEST TO LOWER MS VALLEY. THE CLOSED LOW THAT HAS
   LINGERED EAST OF FL WILL WEAKEN FURTHER AS A WEAKENING AND ELONGATED
   UPPER TROUGH DRIFTS ACROSS THE SOUTHEAST AND TOWARD THE COAST.
   
   AT THE SFC...LEE CYCLONE FORMING OVER WY/NEB/SD BORDERS WILL TRACK
   EAST ACROSS THE MIDDLE MO RIVER VALLEY THROUGH TONIGHT AS A COLD
   FRONT...NOW MOVING INTO NRN MT...SPREADS SOUTH OUT OF MT AND
   EVENTUALLY CATCHES UP WITH SFC LOW IN NRN NEB. A RESERVOIR OF RICH
   LOW LEVEL MOISTURE RESIDING ALONG A DECAYING FRONT OVER TX/OK WILL
   RETURN NWD AS LOW LEVEL SLY FLOW INCREASES ACROSS THE DEVELOPING
   WARM SECTOR AND AHEAD OF A SHARPENING DRYLINE FROM THE TX PNHDL TO
   THE TRIPLE-POINT LOW IN NEB. BY FRIDAY MORNING...THE COLD FRONT WILL
   EXTEND FROM LM SWWD TO CNTRL/SRN KS WITH SEVERAL AREAS OF ACTIVE
   CONVECTION LIKELY ALONG THIS FRONT FROM THE UPPER MIDWEST TO THE
   SRN/CNTRL PLAINS.
   
   ...TX/OK PNHDLS NEWD ACROSS KS TO SRN NEB...
   RELATIVELY STRONG CAPPING AND WEAK FORCING SHOULD INHIBIT TSTM
   DEVELOPMENT ACROSS THE DEVELOPING WARM SECTOR AND AHEAD OF THE
   SHARPENING DRYLINE THROUGH MUCH OF THE DAY. THIS SHOULD ALLOW FOR
   MODERATE TO STRONG INSTABILITY WITH MLCAPE ON THE ORDER OF 1500-2000
   J/KG FROM OK/TX PNHDLS NEWD ACROSS KS INTO SCNTRL NEB. HEATING AND
   DEEP MIXING WILL LIKELY OVERCOME INHIBITION SUFFICIENTLY FOR STORM
   INITIATION TO TAKE PLACE ALONG THE DRYLINE/LEE TROUGH OVER NWRN KS
   BY EVENING. STRONGER EFFECTIVE SHEAR AND SUPERCELL WIND PROFILES
   FROM KS NWD WILL LIKELY PROMOTE LARGE HAIL IN ADDITION TO
   SEVERE/DAMAGING WINDS/DOWNDRAFTS. GREATEST THREAT SHOULD EVOLVE FROM
   CNTRL/NRN KS INTO SRN NEB THROUGH THE EVENING WITH MORE ISOLATED
   STORMS...POSING PRIMARILY A CHANCE FOR DAMAGING OUTFLOW
   WINDS...SOUTH INTO OK/TX.
   
   ONE OR TWO STORM COMPLEXES MAY EVOLVE THROUGH LATE EVENING WITH A
   FEW HAIL/WIND EVENTS POSSIBLE INTO THE NIGHT ACROSS KS AND PERHAPS
   INTO WRN OK OR THE ERN TX PNHDL.
   
   ...ACROSS MIDDLE MO VALLEY FROM IA TO NRN IL LATE...
   LOW LEVEL JET WILL STRENGTHEN AFTER DARK AS STRONGER DYNAMIC FORCING
   SPREADS EAST ACROSS THE MIDDLE MO RIVER VALLEY. PRONOUNCED WARM
   ADVECTION AHEAD OF THE SFC LOW MOVING EAST FROM NEB SHOULD SUPPORT
   THE DEVELOPMENT OF TSTMS ROOTED ABOVE A STABLE BOUNDARY LAYER.
   MUCAPE INTO THIS ZONE OF DEEP CONVECTIVE POTENTIAL SHOULD REACH 1000
   J/KG WITH STRONG SHEAR IN THE CLOUD LAYER AIDING UPDRAFT
   INTENSIFICATION AND THE CHANCE FOR HAIL FROM IA EAST TO NRN IL
   THROUGH LATE TONIGHT/EARLY FRIDAY. THUS...HAIL PROBABILITIES HAVE
   BEEN EXPANDED INTO THESE AREAS WITH THIS UPDATE.
   
   ...VA TIDEWATER ACROSS ERN NC...
   A FEW STRONG TO ISOLATED SEVERE STORMS SEEM POSSIBLE ACROSS THESE
   AREAS AS WEAK FRONT SETTLES SOUTH INTO STRENGTHENING INSTABILITY
   THROUGH THE AFTERNOON. LIFT ACROSS THE REGION MAY ALSO BE AIDED AS A
   WEAK SHORTWAVE TROUGH SPREADS EAST ACROSS THE APPALACHIANS. FLOW
   DOES NOT APPEAR PARTICULARLY STRONG BUT STORMS IN CLUSTERS OR SHORT
   LINES COULD PRODUCE A COUPLE OF DAMAGING WINDS EVENTS UNTIL BOUNDARY
   LAYER COOLING/STABILIZATION SETS IN AFTER SUNSET.
   
   ...MO/AR OZARKS...
   AN AXIS OF POTENTIALLY STRONGER DESTABILIZATION ACROSS THE
   OZARKS...AND THE HINT OF A WEAK DISTURBANCE ALOFT AIDING ASCENT
   ACROSS THE RESIDUAL FRONT ACROSS SRN MO/NRN AR...COULD SUPPORT A
   MORE CONCENTRATED CLUSTER OF STRONG TO ISOLATED SEVERE STORMS IN
   THIS REGION THROUGH THE AFTERNOON. SHEAR WILL NOT BE PARTICULARLY
   STRONG BUT MAY BE OFFSET BY DEGREE OF DESTABILIZATION WITH MLCAPE
   POSSIBLY EXCEEDING 2000 J/KG IN SOME AREAS. A COUPLE OF MARGINAL
   HAIL AND/OR WIND EVENTS SEEM POSSIBLE AND SEVERE PROBABILITIES MAY
   NEED TO BE INCREASED IF IT APPEARS STORM COVERAGE AND PERSISTENCE
   WILL BE GREATER THAN CURRENTLY INDICATED IN AVAILABLE GUIDANCE.
   
   ...NY/OH TO MID-SOUTH...
   NO CHANGES TO LOW PROBABILITY AREAS FROM INITIAL SWODY1...WIDELY
   SCATTERED TO SCATTERED TSTMS ARE EXPECTED TO DEVELOP ALONG WEAK
   FRONTAL ZONE THROUGH THIS AFTERNOON BENEATH DIFFLUENT UPPER-LEVEL
   FLOW AND WEAK INHIBITION. LOW THROUGH MID LEVEL FLOW ACROSS NY-OH
   WILL BE GENERALLY UNIDIRECTIONAL WITH MARGINAL EFFECTIVE SHEAR
   LIMITING STORM POTENTIAL. UPPER/ANVIL-LEVEL FLOW FROM TN NEWD MAY
   ACT TO AID CONVECTIVE VENTILATION ALOFT SO THAT SMALLER SCALE
   MULTICELLULAR STORM ORGANIZATION COULD RESULT IN A COUPLE OF
   HAIL/WIND EVENTS OVER A LARGE REGION.
   
   ..CARBIN/ROGERS.. 09/06/2012
   
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