Sep 7, 2012 1630 UTC Day 1 Convective Outlook
Updated: Fri Sep 7 16:32:31 UTC 2012
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20120907 1630 UTC Day 1 Outlook Graphic
Probabilistic Tornado Graphic
20120907 1630 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 1630 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 1630 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 071628
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1128 AM CDT FRI SEP 07 2012
   
   VALID 071630Z - 081200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS THROUGH EARLY TONIGHT FROM ERN
   OK NEWD ACROSS THE MID MS AND OH VALLEYS...
   
   ...ERN OK NEWD ACROSS THE MID MS/OH VALLEYS THROUGH EARLY TONIGHT...
   
   A STRONG EARLY-SEASON COLD FRONT IS MOVING SWD INTO THE SRN
   PLAINS...AND SEWD ACROSS THE MID MS VALLEY AND UPPER GREAT LAKES. 
   THIS FRONT IS ASSOCIATED WITH AN AMPLIFYING MIDLEVEL TROUGH THAT IS
   PROGRESSING SEWD FROM THE CENTRAL/NRN PLAINS AND THE UPPER MS
   VALLEY.  ON THE MESOSCALE...A SEPARATE REMNANT FRONTAL SEGMENT
   EXTENDS FROM THE SAINT LAWRENCE VALLEY TO NRN INDIANA...WHERE IT IS
   INTERSECTED BY AN OUTFLOW BOUNDARY WITH ONGOING CONVECTION ACROSS
   CENTRAL IL AND NRN INDIANA.  REGIONAL 12Z SOUNDINGS SUGGEST THAT
   SURFACE TEMPERATURES IN THE LOW-MID 80S WITH BOUNDARY LAYER
   DEWPOINTS NEAR 70 F WILL REDUCE CONVECTIVE INHIBITION AND RESULT IN
   MLCAPE NEAR 2500 J/KG IN ADVANCE OF THE ONGOING STORMS.
   THUS...SURFACE-BASED CONVECTION IS LIKELY ACROSS IL/INDIANA/OH THIS
   AFTERNOON...WITH AN ACCOMPANYING RISK FOR DAMAGING WINDS/LARGE HAIL
   GIVEN THE MODERATE INSTABILITY AND THE SRN FRINGE OF THE MODERATE
   MIDLEVEL FLOW/SHEAR.  THE AFTERNOON CONVECTION COULD SPREAD AS FAR E
   AS WRN PA BEFORE WEAKENING THIS EVENING.
   
   FARTHER W AND LATER THIS AFTERNOON...ADDITIONAL THUNDERSTORM
   DEVELOPMENT IS EXPECTED ALONG THE COLD FRONT FROM E/NE OK NEWD
   ACROSS MO/NW AR/SRN IL.  STRONG SURFACE HEATING AND STEEP
   LOW-MIDLEVEL LAPSE RATES WILL PROMOTE STRONG DOWNDRAFTS WITH THE
   POTENTIAL FOR DAMAGING SURFACE WINDS.  CONVECTION WILL LIKELY GROW
   UPSCALE INTO A LINE ALONG THE FRONT...WITH THE SEVERE RISK EXPECTED
   TO PERSIST INTO EARLY TONIGHT AS STORMS SPREAD SEWD ACROSS AR/WRN
   TN/KY.
   
   ..THOMPSON/COHEN.. 09/07/2012
   
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   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 2000Z