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 151240
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0740 AM CDT THU SEP 15 2011
   
   VALID 151300Z - 161200Z
   
   ...NO SVR TSTM AREAS FORECAST...
   
   ...SYNOPSIS...
   A PRONOUNCED MIDLEVEL SHORTWAVE TROUGH OVER THE GREAT LAKES WILL
   ROTATE EWD OVER NEW ENGLAND THROUGH TONIGHT...WHILE AN ASSOCIATED
   SURFACE COLD FRONT MOVES SEWD OFF THE SE NEW ENGLAND AND MID
   ATLANTIC COASTS LATER THIS AFTERNOON/EVENING.  THE COLD FRONT WILL
   ALSO CONTINUE SWD TO THE SE ATLANTIC AND GULF COASTS BY THE END OF
   THE PERIOD.  FARTHER W...THE PERSISTENT UPPER TROUGH OVER AZ WILL
   CONTINUE TO WEAKEN SLOWLY WHILE PROGRESSING EWD TOWARD NM.  A
   POST-FRONTAL UPSLOPE REGIME WILL REMAIN ACROSS THE SRN HIGH
   PLAINS...TRANSITIONING MORE TO A WAA REGIME TONIGHT AS A SLY LLJ
   DEVELOPS FROM TX INTO OK.  OTHERWISE...A SEPARATE NRN STREAM TROUGH
   WILL MOVE INLAND OVER THE PAC NW...WITH A RISK FOR THUNDERSTORMS
   ALONG AN ASSOCIATED COLD FRONT FROM SE ORE ACROSS ID TO SW MT THIS
   AFTERNOON/EVENING.  
   
   ...DELMARVA TO SE NEW ENGLAND THROUGH THIS AFTERNOON...
   THE COLD FRONT IS EXPECTED TO MOVE SLOWLY SEWD TO AN AXIS FROM
   CENTRAL VA TO THE SE NEW ENGLAND COAST BY MID-LATE AFTERNOON. 
   ASCENT ALONG THE FRONT AND SURFACE HEATING E OF THE FRONT/THICK
   CLOUD BAND SHOULD PROMOTE ADDITIONAL THUNDERSTORM DEVELOPMENT THIS
   AFTERNOON.  A NARROW ZONE OF OVERLAP IN THE PRE-FRONTAL INSTABILITY
   /MLCAPE OF 500-1000 J PER KG/ AND THE SERN FRINGE OF THE STRONGER
   MIDLEVEL FLOW COULD SUPPORT A FEW ORGANIZED MULTICELLS/MARGINAL
   SUPERCELL STRUCTURES THIS AFTERNOON...WITH AN ATTENDANT RISK FOR
   ISOLATED DAMAGING WINDS AND MARGINALLY SEVERE HAIL.  RATHER MODEST
   INSTABILITY SUGGESTS THAT THE SEVERE STORM RISK WILL REMAIN TOO
   MARGINAL FOR A CATEGORICAL SLIGHT RISK AREA.  
   
   ...SE AZ/SRN NM/FAR W TX THIS AFTERNOON INTO EARLY TONIGHT...
   THE MIDLEVEL TROUGH OVER AZ WILL ONLY DRIFT EWD...BUT A BELT OF 30+
   KT SWLY MIDLEVEL FLOW WILL BE MAINTAINED OVER SE AZ/NM/W
   TX...ROUGHLY COINCIDENT WITH THE MIDLEVEL DRY SLOT.  SURFACE HEATING
   AND WEAK ASCENT WITH THE MID-UPPER TROUGH WILL SUPPORT SCATTERED
   TSTMS ACROSS SE AZ/SW NM.  THE THICKER CLOUDS WILL LIMIT SURFACE
   HEATING ACROSS W TX...BUT WAA ABOVE THE SHALLOW COOL AIR MASS AND
   UPSLOPE LOW-LEVEL FLOW WILL PROMOTE THUNDERSTORM DEVELOPMENT. 
   MEANWHILE...DEEP-LAYER VERTICAL SHEAR WILL BE MORE FAVORABLE FOR
   SUPERCELLS ACROSS W TX COMPARED TO SE AZ...AND INSTABILITY WILL BE
   RATHER MODEST IN BOTH AREAS.  COMBINING THESE FACTORS...IT APPEARS
   THAT THE STORM ENVIRONMENT COULD SUPPORT A LOW-END RISK OF
   HAIL/DAMAGING WINDS THIS AFTERNOON ACROSS SE AZ/SW NM...AND THIS
   RISK COULD PERSIST INTO EARLY TONIGHT ACROSS FAR W/SW TX IN THE
   DEVELOPING WAA REGIME.
   
   ..THOMPSON/HURLBUT.. 09/15/2011
   
   CLICK TO GET WUUS01 PTSDY1 PRODUCT

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z