THERE IS A SLGT RISK OF SVR TSTMS LATE THIS AFTERNOON AND EVENING ACROSS PARTS OF THE UPPER GREAT LAKES SOUTHEASTWARD THROUGH THE UPPER OH VALLEY AND MID ATLANTIC COAST REGION

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 041951
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0251 PM CDT WED JUL 04 2012
   
   VALID 042000Z - 051200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS LATE THIS AFTERNOON AND EVENING
   ACROSS PARTS OF THE UPPER GREAT LAKES SOUTHEASTWARD THROUGH THE
   UPPER OH VALLEY AND MID ATLANTIC COAST REGION...
   
   ...20Z OUTLOOK UPDATE...
   CHANGES TO PRIOR OUTLOOK ARE GENERALLY CONFINED TO PORTIONS OF THE
   UPPER GREAT LAKES REGION...MOSTLY TO ACCOUNT FOR ONGOING CONVECTIVE
   ACTIVITY.  POTENTIAL EVOLUTION INTO THE EVENING HOURS IS STILL NOT
   PARTICULARLY CLEAR...BUT A SIGNIFICANT...SIZABLE CONVECTIVE CLUSTER
   HAS ALREADY EVOLVED ACROSS NORTHERN MINNESOTA ...AND THIS SEEMS TO
   SUPPORT INCREASING PROBABILITIES FOR SEVERE HAIL AND WIND ACROSS AT
   LEAST PARTS OF MINNESOTA TO THE WEST AND SOUTHWEST OF
   DULUTH...THROUGH NORTHERN WISCONSIN.
   
   STRONGER FORCING FOR UPWARD VERTICAL MOTION ASSOCIATED WITH CANADIAN
   CYCLONE WILL REMAIN NORTH OF THE INTERNATIONAL BORDER.  THE
   MID-LEVEL LOW CENTER IS NOW OVER NORTHERN SASKATCHEWAN...AND STILL
   LIFTING NORTHEASTWARD...WITH A TENDENCY FOR LARGER SCALE MID-LEVEL
   HEIGHT RISES OVER THE UPPER MISSISSIPPI VALLEY/GREAT LAKES REGION. 
   HOWEVER...A REMNANT IMPULSE WITHIN THE MONSOONAL REGIME ON THE
   NORTHERN PERIPHERY OF THE SUBTROPICAL RIDGING COULD STILL CONTRIBUTE
   TO CONVECTIVE DEVELOPMENT ACROSS MINNESOTA AND WISCONSIN LATE THIS
   AFTERNOON AND EVENING.
   
   ONGOING ACTIVITY MAY CONTINUE EASTWARD WITH A SEVERE HAIL AND WIND
   THREAT THROUGH THE MINNESOTA ARROWHEAD.  20-30 KT WESTERLY DEEP
   LAYER MEAN FLOW PROBABLY WILL MAINTAIN EASTWARD MOTION INTO THE LAKE
   SUPERIOR VICINITY...WHERE IT IS STILL NOT CLEAR WHETHER NEAR SURFACE
   INFLOW OF COOL AIR FROM THE LAKE WILL STRONGLY WEAKEN IT...OR
   LOWER/MID TROPOSPHERIC WARM ADVECTION WILL BE ABLE TO MAINTAIN
   SIGNIFICANT ELEVATED CONVECTION INTO THE UPPER PENINSULA OF
   MICHIGAN.
   
   IT MAY BE THAT THE SUBTROPICAL PERTURBATION CONTRIBUTES TO A
   DISTINCT NEW CLUSTER OF STORMS TO THE SOUTHWEST OF THE ONGOING
   ACTIVITY...WHERE UNINTERRUPTED INFLOW OF VERY MOIST AIR IN THE
   PRESENCE OF SIZABLE CAPE AND MODEST SHEAR COULD PROVE FAVORABLE TO A
   FORWARD/EASTWARD PROPAGATING MESOSCALE CONVECTIVE SYSTEM ACROSS
   NORTHERN WISCONSIN THIS EVENING...PERHAPS LOWER MICHIGAN OVERNIGHT.
   
   OTHERWISE...LOW-LEVEL WARM ADVECTION BENEATH LIGHT TO MODERATE
   NORTHWEST MID-LEVEL FLOW COULD STILL SUPPORT ADDITIONAL EVOLVING
   CLUSTERS OF STORMS WITH RISK FOR DAMAGING WINDS AND HAIL ACROSS
   LOWER MICHIGAN INTO PARTS OF THE UPPER OHIO VALLEY AND MID ATLANTIC
   COAST STATES LATE THIS AFTERNOON AND EVENING.
   
   ..KERR.. 07/04/2012
   
   .PREV DISCUSSION... /ISSUED 1134 AM CDT WED JUL 04 2012/
   
   ...NRN MN/WI THROUGH THIS EVENING...
   THE PRIMARY NRN STREAM SHORTWAVE TROUGH NOW OVER SK WILL CREST THE
   RIDGE AND BEGIN TO MOVE MORE EWD OVER MB/WRN ONTARIO LATER TODAY
   INTO TONIGHT.  AT THE SURFACE...A LOW IN ERN ND THIS MORNING WILL
   SLOWLY WEAKEN BY LATE EVENING...AS A SURFACE WARM FRONT LIFTS NWD
   ACROSS NRN MN/WI...AND A COLD FRONT PROGRESSES SEWD ACROSS NEB AND
   THE ERN DAKOTAS.  A RESERVOIR OF LOW 70S BOUNDARY LAYER DEWPOINTS
   BENEATH STEEP MIDLEVEL LAPSE RATES...IN COMBINATION WITH DAYTIME
   HEATING...WILL SUPPORT A CORRIDOR OF STRONG INSTABILITY ALONG AND S
   OF THE WARM FRONT IN MN/WI...WHERE MLCAPE WILL RANGE FROM 3000-4000
   J/KG.
   
   ONGOING STORMS ACROSS NW MN SHOULD PERSIST THROUGH THE DAY AND
   SPREAD EWD ACROSS NRN MN...NEAR AND JUST N OF THE WARM FRONT. 
   DEEP-LAYER AND LOW-LEVEL VERTICAL SHEAR WILL BE SOMEWHAT STRONGER ON
   THE IMMEDIATE COOL SIDE OF THE BOUNDARY...WHERE BOTH ORGANIZED
   MULTICELL CLUSTER AND SOME SUPERCELL STRUCTURES WILL BE POSSIBLE. 
   LARGE HAIL AND DAMAGING WINDS WILL BE THE MAIN SEVERE THREATS WITH
   THIS ACTIVITY.  
   
   ...NRN WI TO LOWER MI THIS AFTERNOON/EVENING...
   FARTHER SE ALONG THE WARM FRONT ACROSS WI/LOWER MI...STRONG SURFACE
   HEATING AND STRONG INSTABILITY WILL BE PRESENT.  THE ONLY CLEAR
   FOCUS FOR STORM INITIATION WILL BE LOW-LEVEL CONVERGENCE ALONG THE
   BOUNDARY...WHILE A DIFFUSE SPEED MAX ALOFT MOVES ESEWD FROM WRN
   UPPER MI TOWARD LOWER MI.  STORM COVERAGE REMAINS QUESTIONABLE ALONG
   THIS CORRIDOR...BUT THE STEEP LAPSE RATES/LARGE BUOYANCY WILL
   SUPPORT A CONDITIONAL RISK FOR LARGE HAIL/DAMAGING WINDS...PRIMARILY
   WITH MULTICELL STORMS.
   
   ...ERN OH/WRN PA/WV/NRN VA THIS AFTERNOON/EVENING...
   THE FOCUS FOR STORM DEVELOPMENT IS STILL A BIT UNCERTAIN...BUT
   STRONG SURFACE HEATING IS WELL UNDERWAY ACROSS THE AREA...WHERE
   MODERATE-STRONG INSTABILITY IS EXPECTED THIS AFTERNOON.  THE REMNANT
   COLD POOL WITH THE ONGOING NW PA STORMS COULD BE ASSOCIATED WITH NEW
   STORM DEVELOPMENT THIS AFTERNOON...AS WELL AS SURFACE HEATING OVER
   THE HIGHER TERRAIN.  ANY STORMS/CLUSTERS THAT DO FORM WILL BE
   CAPABLE OF PRODUCING DAMAGING DOWNBURST WINDS...AND SOME HAIL.
   
   ...UPSTATE NY AREA THIS AFTERNOON...
   A SHORTWAVE TROUGH OVER QUEBEC WILL ROTATE SEWD OVER NRN NY/NRN NEW
   ENGLAND THIS AFTERNOON/EVENING...ALONG WITH AN ASSOCIATED SURFACE
   COLD FRONT.  VERTICAL SHEAR WILL BE SUFFICIENT FOR ORGANIZED DEEP
   CONVECTION...BUT POOR LAPSE RATES WILL TEND TO LIMIT BUOYANCY. 
   THUS...WILL MAINTAIN LOW WIND/HAIL PROBABILITIES IN THIS UPDATE.
   PREVIOUS FORECAST REMAINS ON TRACK.
   
   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z
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