Sep 5, 2012 0100 UTC Day 1 Convective Outlook
Updated: Wed Sep 5 01:08:30 UTC 2012
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20120905 0100 UTC Day 1 Outlook Graphic
Probabilistic Tornado Graphic
20120905 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
20120905 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
20120905 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 050104
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0804 PM CDT TUE SEP 04 2012
   
   VALID 050100Z - 051200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE NRN
   PLAINS...CNTRL PLAINS AND UPPER MS VALLEY...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE CNTRL GULF
   COAST...
   
   ...UPPER MS VALLEY/NRN PLAINS...
   THE LATEST WATER VAPOR IMAGERY SHOWS WLY FLOW ACROSS THE UPPER MS
   VALLEY WITH A SUBTLE SHORTWAVE TROUGH EXTENDING SWD FROM NE MN INTO
   WI. SEVERAL CLUSTERS OF STRONG THUNDERSTORMS ARE ONGOING JUST AHEAD
   OF THE TROUGH AXIS ALONG A CORRIDOR OF MODERATE TO STRONG
   INSTABILITY. THE STORMS ARE EXPECTED TO CONTINUE EWD AS LOW-LEVEL
   JET INCREASES THIS EVENING WITH MCS DEVELOPMENT POSSIBLE ACROSS ERN
   WI. THE STORMS MAY ALSO IMPACT EXTREME NRN IL LATER THIS EVENING.
   
   THE GREEN BAY AND DAVENPORT 00Z SOUNDINGS BOTH SHOW A STRONGLY
   UNSTABLE AIRMASS WITH MLCAPE VALUES OF 200O TO 2500 J/KG. IN
   ADDITION...THE SOUNDINGS HAVE ABOUT 30 KT OF DEEP LAYER SHEAR WITH
   STEEP LAPSE RATES IN THE MID-LEVELS. THIS ENVIRONMENT SHOULD
   CONTINUE SUPPORT SUPERCELLS THIS EVENING AND LARGE HAIL APPEARS
   LIKELY WITH THE STRONGER UPDRAFTS. THE MORE DOMINANT SUPERCELLS
   COULD PRODUCE HAIL GREATER THAN 2 INCHES IN DIAMETER. FOR THIS
   REASON...HAVE LEFT A HATCHED AREA FOR VERY LARGE HAIL ACROSS SCNTRL
   WI. AS CELL MERGERS TAKE PLACE EARLY THIS EVENING AND AN MCS
   ORGANIZES...THE WIND DAMAGE THREAT SHOULD INCREASE. HAVE DRAWN THE
   SLIGHT RISK EWD TO THE SHORE OF LAKE MICHIGAN AND SWD INTO EXTREME
   NRN IL. IN ADDITION...HAVE EXTENDED THE 30 PERCENT WIND DAMAGE
   PROBABILITY EWD ACROSS SRN WI.
   
   ...NRN PLAINS...
   THE LATEST WATER VAPOR IMAGERY SHOWS AN UPPER-LEVEL TROUGH MOVING
   EWD ACROSS THE NRN HIGH PLAINS. AHEAD OF THIS FEATURE...SEVERAL
   VORTICITY MAXIMA ARE ANALYZED ACROSS THE DAKOTAS PROVIDING SUPPORT
   FOR THE ONGOING CONVECTION. AT THE SFC...A 1003 MB LOW IS LOCATED
   ACROSS SERN SD WITH A CLUSTER OF STRONG TO SEVERE THUNDERSTORMS JUST
   TO THE NORTH OF THE LOW IN SERN SD. SHORT-TERM MODEL FORECASTS
   SUGGEST THIS ACTIVITY WILL PERSIST THROUGH MUCH OF THE EVENING
   MOVING ACROSS NRN IA AND SWRN MN. MESOANALYSIS AHEAD OF THE STORMS
   HAS AN AXIS OF MODERATE INSTABILITY FROM CNTRL IA EXTENDING NEWD
   INTO SE SD WITH MLCAPE VALUES IN THE 1500 TO 2500 J/KG RANGE. IN
   ADDITION...THE WSR-88 VWP AT SIOUX FALLS SHOWS AN IMPRESSIVE SHEAR
   ENVIRONMENT WITH ABOUT 60 KT OF DEEP LAYER SHEAR. THIS ENVIRONMENT
   SHOULD CONTINUE TO SUPPORT SUPERCELL DEVELOPMENT AND LARGE HAIL WILL
   BE LIKELY WITH THE STRONGER UPDRAFTS. HOWEVER...AS CELLS MERGE AND A
   BROKEN LINE MOVES ACROSS SRN MN AND NRN IA EARLY THIS EVENING...THE
   WIND DAMAGE THREAT MAY INCREASE. DUE TO VERY STEEP LOW-LEVEL LAPSE
   RATES AND INCREASING LOW-LEVEL FLOW EARLY THIS EVENING...AN ENHANCED
   WIND DAMAGE THREAT WILL BE POSSIBLE. HAVE EXTENDED THE 30 PERCENT
   WIND DAMAGE PROBABILITY FROM THE SIOUX FALLS AREA EWD ACROSS NRN IA
   AND FAR SRN MN.
   
   ...CNTRL GULF COAST STATES...
   A CLUSTER OF STRONG TO SEVERE THUNDERSTORMS IS CURRENTLY ONGOING IN
   SRN MS AND SW AL ON THE WRN SIDE OF AN UPPER-LEVEL TROUGH EVIDENT ON
   WATER VAPOR IMAGERY. THE CONVECTION IS LOCATED IN A STRONGLY
   UNSTABLE AIRMASS WHERE SFC DEWPOINTS ARE IN THE MID 70S F. IN
   ADDITION TO THE MOIST BOUNDARY LAYER...THE 00Z SOUND AT NEW ORLEANS
   SHOWS MLCAPE AROUND 2500 J/KG WITH A LOW-LEVEL LAPSE RATE
   APPROACHING 8.0 C/KM. THIS ENVIRONMENT ALONG WITH ABOUT 20 KT OF
   DEEP LAYER SHEAR SHOULD BE FAVORABLE FOR MULTICELLS WITH WIND DAMAGE
   POTENTIAL. THIS SEVERE THREAT COULD PERSIST FOR A FEW MORE HOURS
   BEFORE THE ACTIVITY APPROACHES THE COASTAL AREAS LATER THIS EVENING.
   
   
   ...SRN AND CNTRL PLAINS...
   SEVERAL CLUSTERS OF STRONG TO SEVERE THUNDERSTORMS ARE ONGOING FROM
   NEAR SALINA SWD INTO NWRN OK. THE ACTIVITY IS LOCATED JUST AHEAD OF
   A SUBTLE UPPER-LEVEL DISTURBANCE. THE AIRMASS FROM CNTRL KS INTO NW
   OK IS MODERATELY UNSTABLE WITH MESOANALYSIS SHOWING MLCAPE OF 1000
   TO 2000 J/KG. IN ADDITION...REGIONAL WSR-88D VWPS HAVE 30 TO 40 KT
   OF DEEP LAYER SHEAR SUGGESTING THE ENVIRONMENT SHOULD SUPPORT
   ISOLATED SEVERE STORM DEVELOPMENT FOR A LITTLE WHILE LONGER THIS
   EVENING. HOWEVER...AS INSTABILITY DECREASES...THE SEVERE THREAT
   SHOULD BECOME INCREASINGLY MARGINAL. HAIL AND STRONG WIND GUSTS
   SHOULD BE THE PRIMARY THREATS WITH THE ACTIVITY.
   
   ..BROYLES.. 09/05/2012
   
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