Sep 1, 2012 2000 UTC Day 1 Convective Outlook
Updated: Sat Sep 1 19:59:35 UTC 2012
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20120901 2000 UTC Day 1 Outlook Graphic
Probabilistic Tornado Graphic
20120901 2000 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
20120901 2000 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
20120901 2000 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 011955
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0255 PM CDT SAT SEP 01 2012
   
   VALID 012000Z - 021200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE LWR MS AND LWR TN
   VLYS INTO THE LWR OH VLY...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PORTIONS OF THE GREAT
   BASIN/INTERMOUNTAIN REGION...
   
   ...AR/MIDDLE MS VALLEY/LOWER OH VALLEY...
   LIMITED CHANGES IN RISK AREAS/FORECAST REASONING...ALTHOUGH
   CATEGORICAL SLIGHT RISK/TORNADO PROBABILITIES WERE EXTENDED A BIT
   FARTHER NORTH ACROSS CENTRAL IL. REFERENCE TORNADO WATCHES 602/603
   FOR ADDITIONAL DETAILS.
   
   ...GREAT BASIN/INTERMOUNTAIN REGION...
   SLIGHT RISK HAS BEEN INTRODUCED FOR PORTIONS OF NORTHEAST NV INTO
   UT/SOUTHERN ID/SOUTHWEST WY IN ACCORDANCE WITH SEVERE TSTM WATCH
   604. DAMAGING WINDS AND SEVERE HAIL WILL BE THE PRIMARY HAZARDS.
   
   ...ELSEWHERE...
   NO CHANGES NEEDED...SEE PRIOR DISCUSSION BELOW AND ANY SUBSEQUENT
   MESOSCALE DISCUSSIONS.
   
   ..GUYER.. 09/01/2012
   
   .PREV DISCUSSION... /ISSUED 1129 AM CDT SAT SEP 01 2012/
   
   ...SYNOPSIS...
   REMNANT CIRCULATION OF EX-HRCN ISAAC WILL BECOME ABSORBED WITHIN THE
   WLYS LATER THIS PERIOD AS BC UPR LOW PIVOTS ENE INTO WRN
   MB...ENHANCING WSW FLOW FROM THE NRN GRT BASIN TO THE NRN PLNS/UPR
   MS VLY. OTHERWISE...WEAKER DISTURBANCES WILL CONTINUE TO PROGRESS
   ENE ACROSS THE INTERMOUNTAIN WEST...AND ESE FROM THE UPR GRT LKS TO
   THE NEW ENGLAND/MID ATLANTIC CST. 
   
   ...AR TO LWR OH VLY THIS AFTN/EVE...
   AREA VWP DATA SHOW A BELT OF SEASONABLY STRONG /APPROXIMATELY 40 KT/
   LWR TROPOSPHERIC FLOW SKIRTING SRN AND ERN SIDE OF REMNANT
   CIRCULATION OF ISAAC. ATTM THE CIRCULATION IS CENTERED JUST SW OF
   COLUMBIA MISSOURI. THE CENTER SHOULD CONTINUE SLOWLY E TO NEAR ST
   LOUIS THIS EVE...AND REACH S CNTRL IL EARLY SUN.  
   
   CURRENT SATELLITE DATA SUGGEST THAT MID LVL DRY SLOT NOW IN SE
   MO/NRN AR SHOULD MOVE ENE INTO SRN IL LATER TODAY. INITIAL
   IMPRESSION IS THAT THIS SHOULD SERVE TO ENHANCE THE POTENTIAL FOR
   SFC HEATING/DESTABILIZATION IN CORRIDOR OF BKN LOW-LVL CLOUDS THAT
   ATTM EXTENDS FROM NR AR NEWD INTO SRN/CNTRL IL...ROUGHLY COINCIDENT
   WITH AFOREMENTIONED BELT OF STRONG LWR TROPOSPHERIC FLOW.
   
   AMPLE LOW TO MID LVL SPEED AND DIRECTIONAL SHEAR SHOULD REMAIN
   PRESENT TO SUPPORT LOW-LVL UPDRAFT ROTATION/MESOS THROUGH THIS EVE
   FROM CNTRL/ERN AR E/NEWD INTO THE LWR OH/TN VLY. IN ADDITION...BOTH
   SATELLITE AND MODELS SUGGEST THAT THE REGION WILL EXPERIENCE LARGE
   SCALE UVV THAT...WITH SFC HEATING...COULD FOSTER STORM DEVELOPMENT.
   ON THE OTHER HAND...MID-LVL TEMPS WILL BE QUITE WARM /AROUND MINUS
   3-4 C AT 500 MB/...AND HIGH-LVL FLOW WEAK. IT ALSO APPEARS THAT THE
   STRONGEST FORCING FOR ASCENT MAY NOT REACH THE LOW LVL MOIST AXIS
   UNTIL EARLY EVE. THESE FACTORS COULD HINDER...OR AT LEAST
   DELAY...ROBUST STORM DEVELOPMENT.
   
   AT ANY RATE...GIVEN DEGREE OF LOW-LVL HODOGRAPH CURVATURE AND THE
   PRESENCE OF RICH LOW-LVL MOISTURE /DEWPOINTS IN THE LOW 70S
   F/...SITUATION LOOKS A LEAST AS FAVORABLE AS YESTERDAY'S AS FAR AS
   TORNADIC POTENTIAL IS CONCERNED..ESPECIALLY OVER THE NRN HALF OF THE
   SLGT RISK. THE POTENTIAL ALSO WILL EXIST FOR A FEW LOCALLY DMGG WIND
   GUSTS...MAINLY IN SRN HALF OF THE RISK AREA. IF THE ARRIVAL OF
   STRONGER LARGE-SCALE FORCING FOR ASCENT IS INDEED DELAYED TIL EARLY
   EVE...THE SVR THREAT...INCLUDING BOTH WIND GUSTS AND
   TORNADOES...COULD PERSIST INTO EARLY TNGT EWD INTO WRN PARTS OF
   KY/TN AND PERHAPS FAR NRN MS.
   
   ...NRN GRT BASIN NE TO NRN PLNS THIS AFTN INTO TNGT...
   LOW AMPLITUDE DISTURBANCES ACCELERATING NEWD AHEAD OF BC/AB UPR
   TROUGH EXPECTED TO FOSTER SCTD SMALL CLUSTERS OF STRONG TO POSSIBLY
   LOCALLY SVR STORMS LATER THIS AFTN INTO TNGT FROM UT/ERN ID E/NE
   INTO MUCH OF WY AND CNTRL/ERN MT. THE MAIN THREAT WITH THIS ACTIVITY
   SHOULD BE DMGG WIND GIVEN 30 KT LWR TROPOSPHERIC MEAN FLOW AND STEEP
   LOW LVL LAPSE RATES.
   
   SOME POTENTIAL ALSO WILL EXIST FOR A LOOSELY-ORGANIZED CLUSTER OF
   FORWARD-PROPAGATING STORMS TO EVOLVE NEAR LEE TROUGH OVER ERN MT
   AND/OR NE WY TOWARD EVE. SUCH A SYSTEM...WERE IT TO DEVELOP...COULD
   MOVE NE INTO WRN AND NRN ND POSING A RISK FOR DMGG WIND GIVEN VERY
   WARM/DEEP MIXED ENVIRONMENT...NOCTURNALLY/DYNAMICALLY STRENGTHENING
   LLJ...AND AT LEAST THE GLANCING INFLUENCE OF FORCING FOR ASCENT
   ASSOCIATED WITH BC/AB/MB UPR TROUGH. LOW SVR PROBABILITIES HAVE BEEN
   EXTENDED INTO ND FOR THIS POSSIBLE SCENARIO.  
   
   ...MID ATLANTIC THIS AFTN...
   WDLY SCTD PULSE STORMS MAY FORM ALONG AND AHEAD OF BACK-DOOR FRONT
   EDGING S ACROSS ERN PA/NJ.  MODEST...DEEP UNIDIRECTIONAL NW FLOW AND
   RELATIVELY STEEP LOW LVL LAPSE RATES MAY FOSTER ISOLD LOCALLY DMGG
   GUSTS BEFORE SUNSET ACROSS PARTS OF WV/MD/DE/VA.
   
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