Jul 3, 2012 1300 UTC Day 1 Convective Outlook
Updated: Tue Jul 3 12:46:29 UTC 2012
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20120703 1300 UTC Day 1 Outlook Graphic
Probabilistic Tornado Graphic
20120703 1300 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
20120703 1300 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
20120703 1300 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 031242
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0742 AM CDT TUE JUL 03 2012
   
   VALID 031300Z - 041200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON INTO TONIGHT
   ACROSS PORTIONS OF THE NRN HIGH PLAINS...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON AND EVENING OVER
   PARTS OF THE GREAT LAKES AND OH VALLEY...
   
   ...SYNOPSIS...
   
   STRONG SHORTWAVE TROUGH AND ASSOCIATED 60-70 KT MIDLEVEL JET STREAK
   OVER THE NRN INTERMOUNTAIN REGION WILL PROGRESS NEWD INTO
   ALBERTA/SASKATCHEWAN WITH THE SRN FRINGE OF HEIGHT FALLS/FORCING FOR
   ASCENT SPREADING ACROSS N-CNTRL/NERN MT.  DOWNSTREAM FROM THIS
   FEATURE...A LOWER-AMPLITUDE SHORTWAVE TROUGH OVER THE UPPER GREAT
   LAKES WILL TRANSLATE SEWD THROUGH THE LOWER GREAT LAKES TO THE
   VICINITY OF THE NEW ENGLAND AND MID ATLANTIC COASTS BY 04/12Z.
   
   AT THE SURFACE...COLD FRONT FROM N-CNTRL MN SWWD INTO SRN SD WILL
   SETTLE SEWD ACROSS PORTIONS OF THE UPPER GREAT LAKES. THE WRN
   EXTENSION OF THE COLD FRONT WHICH HAS STALLED FROM SRN SD INTO CNTRL
   MT WILL LIFT NWD IN ADVANCE OF A PACIFIC FRONT ADVANCING FROM THE
   NRN ROCKIES INTO WRN DAKOTAS.  FARTHER E...A WARM FRONT WILL LIFT
   NEWD THROUGH THE LOWER GREAT LAKES INTO THE HUDSON VALLEY.
   
   ...NRN HIGH PLAINS...
   
   LOW-LEVEL MASS RESPONSE TO NRN ROCKIES SHORTWAVE TROUGH --MANIFEST
   AS A 30-35 KT LLJ-- WILL ENHANCED THE NWWD FLUX OF A MOIST
   POST-FRONTAL BOUNDARY LAYER OVER THE DAKOTAS INTO ERN MT TODAY
   ALONG/N RETREATING WARM FRONT.  THIS PROCESS WILL OCCUR BENEATH A
   PRONOUNCED EML...YIELDING AFTERNOON MLCAPE VALUES OF 1500-2500 J/KG.
   THE STRONGEST FORCING FOR ASCENT AND RESULTANT GREATER STORM
   COVERAGE ON THE PACIFIC FRONT IS ANTICIPATED N OF THE INTERNATIONAL
   BORDER.  HOWEVER...THE GLANCING INFLUENCE OF UPPER SYSTEM MAY BE
   SUFFICIENT TO SUPPORT ISOLATED-WIDELY SCATTERED STORMS BY LATE
   AFTERNOON OR EVENING ACROSS PORTIONS OF NERN MT.  IN THE PRESENCE OF
   A VERTICALLY VEERING WIND FIELD AND 35-40 KT OF DEEP-LAYER
   SHEAR...SETUP WILL PROMOTE SUPERCELLS AND BOWING STRUCTURES WITH A
   RISK FOR LARGE HAIL AND DAMAGING WINDS SPREADING EWD INTO ND
   TONIGHT.
   
   ...GREAT LAKES TO MID ATLANTIC COAST...
   
   WIDESPREAD CONVECTIVE OUTFLOW AND RESIDUAL CLOUD COVER ASSOCIATED
   WITH MULTIPLE TSTM CLUSTERS/MCSS ONGOING OVER THE GREAT LAKES CAST
   CONSIDERABLE UNCERTAINTY ON AIR MASS DESTABILIZATION AND LOCATION
   AND TIMING OF DIURNALLY ENHANCED STORM DEVELOPMENT LATER TODAY. 
   BASED ON CURRENT OBSERVATIONAL DATA AND MODEL FORECASTS...IT APPEARS
   THAT SOME SUBSET OF ONGOING STORMS MAY RE-INTENSIFY BY LATE MORNING
   OR AFTERNOON ACROSS PARTS OF THE UPPER OH VALLEY INTO LOWER GREAT
   LAKES WITHIN DESTABILIZING AIR MASS INVOF RETREATING WARM FRONT. 
   OTHER STRONG-SEVERE STORMS WILL BE POSSIBLE THIS AFTERNOON AND
   EVENING ALONG RESIDUAL OUTFLOW BOUNDARIES AND SYNOPTIC COLD FRONT
   ACROSS PORTIONS OF THE UPPER GREAT LAKES.
   
   WITH RESPECT TO THE LATTER...12Z MPX SOUNDING SAMPLED STEEP MIDLEVEL
   LAPSE RATES AND A MOIST BOUNDARY LAYER ON THE WRN FRINGE OF ONGOING
   TSTMS.  CURRENT THINKING IS THAT PREVAILING WLY DEEP-LAYER FLOW
   FIELD SHOULD ALLOW A SIMILAR THERMODYNAMIC ENVIRONMENT TO BE
   ADVECTED ACROSS THE UPPER GREAT LAKES IN THE WAKE OF NOCTURNAL
   STORMS...AND AHEAD OF COLD FRONT.  THE POTENTIAL FOR MODERATE
   INSTABILITY /I.E. MLCAPE VALUES OF 1500-2500 J PER KG/ WILL ALIGN
   WITH MODERATELY STRONG WLY FLOW /REF. 12Z MPX AND GRB SOUNDINGS/ TO
   SUPPORT A THREAT FOR ORGANIZED STORM MODES INCLUDING BOWS/SUPERCELLS
   CAPABLE OF DAMAGING WINDS AND LARGE HAIL.
   
   UPSCALE GROWTH OF DAYTIME STORMS INTO MULTIPLE NIGHTTIME
   COMPLEXES/MCSS IS ANTICIPATED WITH AN ISOLATED THREAT FOR HAIL AND
   LOCALLY DAMAGING WINDS SPREADING EWD TOWARD THE HUDSON VALLEY AND
   MID ATLANTIC COAST.
   
   ...CNTRL/SRN APPALACHIANS INTO GULF COAST STATES...
   
   12Z REGIONAL SOUNDINGS INDICATE THE POTENTIAL FOR MODERATE-STRONG
   AIR MASS DESTABILIZATION TODAY OWING TO THE PRESENCE OF A MOIST
   BOUNDARY LAYER AND DAYTIME HEATING.  TSTMS ARE EXPECTED TO INCREASE
   IN COVERAGE AND INTENSITY THIS AFTERNOON ALONG THE HIGH
   TERRAIN...DEVELOPING SEA BREEZE FRONT...AND OUTFLOW BOUNDARIES
   REMNANT FROM MONDAY AFTERNOON/EVENING STORMS.  WHILE WEAK VERTICAL
   SHEAR WILL LIMIT THE POTENTIAL FOR STORM
   ORGANIZATION/LONGEVITY...ISOLATED OCCURRENCES OF DAMAGING WIND AND
   HAIL ARE POSSIBLE.
   
   ..MEAD/HURLBUT.. 07/03/2012
   
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