SPC AC 272017
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0317 PM CDT WED AUG 27 2003
   
   VALID 272000Z - 281200Z
   
   THERE IS A SLGT RISK OF SVR TSTMS TO THE RIGHT OF A LINE FROM 45 S
   WAL RIC HTS 45 NE CRW HLG PIT PSB 20 SSW JFK
   
   THERE IS A SLGT RISK OF SVR TSTMS TO THE RIGHT OF A LINE FROM 40 E
   RRT RWF 30 SSW YKN BUB MHN CDR 35 SE 81V REJ P24 55 NW MOT
   
   GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM 25 ENE ECG RWI SOP
   CAE 10 SSW AGS 50 WNW SAV 10 SSE SSI ...CONT... 10 ENE CRP 55 NW LRD
   ...CONT... CZZ PMD 10 NNW NID ELY 10 NE ENV 10 SE SUN S80 40 N FCA
   ...CONT... 10 SW CMX 25 S IWD 10 SSW RST FOD LWD 30 N IRK 30 SSE BRL
   BMI SBN BUF SYR 30 S BTV 15 NE EFK
   
   ...THERE IS A SLGT RISK OF SVR TSTMS THRU EARLY EVE ACROSS THE
   NORTHERN MID ATLANTIC COAST STATES....
   
   ...THERE IS A SLGT RISK OF SVR TSTMS LATE THIS AFTN AND TONIGHT
   ACROSS PARTS OF THE NORTHERN PLAINS....
   
   ...OHIO VALLEY INTO MID ATLANTIC COAST...
   WATER VAPOR IMAGERY SUPPORTS MODEL PROGS INDICATING SEVERAL WAVES
   EMBEDDED WITHIN WEAK SUBTROPICAL BRANCH OF THE WESTERLIES...WHICH
   CURVES CYCLONICALLY FROM THE NORTH CENTRAL PLAINS THROUGH THE LOWER
   OHIO VALLEY INTO THE MID ATLANTIC STATES.  ONE WAVE IS PROGRESSING
   OUT OF THE LOWER OHIO VALLEY INTO THE CENTRAL APPALACHIANS...AND
   WILL CONTINUE EASTWARD ACROSS MID ATLANTIC COAST AREAS THIS EVENING.
    THIS IS JUST TO THE SOUTH OF STRONG POLAR JET...REMAINING NEAR THE
   CANADIAN U.S. BORDER...WITH EMBEDDED VIGOROUS SHORT WAVE TROUGH
   SWEEPING ACROSS QUEBEC AND THE ST. LAWRENCE VALLEY.  CONFIGURATION
   OF UPPER FEATURES HAS CONTRIBUTED TO STRONG DIVERGENT UPPER FLOW
   FIELD...WHICH HAS SUPPORTED EVOLUTION OF CONVECTIVE CLUSTER NOW
   SPREADING ACROSS PARTS OF SOUTHWESTERN PENNSYLVANIA AND NORTHERN
   WEST VIRGINIA.
   
   CONVECTIVE SYSTEM APPEARS LIKELY TO CONTINUE EVOLVING/INTENSIFYING
   LATE THIS AFTERNOON AS IT PROGRESSES EAST OF THE NORTH CENTRAL
   APPALACHIANS INTO MOIST AND MODERATELY UNSTABLE ENVIRONMENT ACROSS
   THE NORTHERN MID ATLANTIC COAST STATES.  CONVECTIVELY GENERATED
   THERMAL BOUNDARY  EXTENDING FROM THE EASTERN WEST VIRGINIA PANHANDLE
   THROUGH NORTHERN VIRGINIA WILL PROVIDE A FOCUS FOR PROPAGATION OF
   STORMS...AIDED BY 30 TO 40 KT MID-LEVEL FLOW ON SOUTHERN FRINGE OF
   STRONGER WESTERLIES.  THERMODYNAMIC ENVIRONMENT REMAINS SUFFICIENT
   FOR THE DEVELOPMENT OF A SUBSTANTIAL COLD POOL/ MESO
   HIGH...ACCOMPANIED BY GUSTY/DAMAGING WINDS IN WAKE OF ASSOCIATED
   GUST FRONT...WHICH WILL PROGRESS OFFSHORE DURING THE MID EVENING
   HOURS.
   
   OTHERWISE...DAYTIME HEATING/WEAKENING CAP HAS ALLOWED SCATTERED
   CONVECTIVE DEVELOPMENT ALONG/AHEAD OF STALLING SURFACE COLD FRONT
   ACROSS THE LOWER OHIO VALLEY.  FLOW FIELDS/VERTICAL SHEAR PROFILES
   HAVE BECOME QUITE WEAK ACROSS THIS REGION...WITH MAIN SHORT WAVE NOW
   PROGRESSING INTO THE EASTERN CANADIAN PROVINCES.  THIS APPEARS
   LIKELY TO MINIMIZE OVERALL SEVERE THREAT WITH THIS ACTIVITY...WHICH
   SHOULD DIMINISH WITH LOSS OF DAYTIME HEATING.
   
   ...NORTHERN PLAINS...
   SHORT WAVE TROUGH LIFTING OUT OF THE NORTH CENTRAL ROCKIES...AND
   UPSTREAM SHORT WAVE ALONG THE NORTHWESTERN CANADIAN/U.S. BORDER WILL
   CONTINUE TO GRADUALLY EVOLVE INTO LARGER SCALE TROUGH...WHILE
   PROGRESSING EASTWARD LATE THIS AFTERNOON AND TONIGHT.  LOW-LEVEL
   CYCLOGENESIS IS ALREADY OCCURRING ACROSS THE NORTH CENTRAL HIGH
   PLAINS IN RESPONSE TO THIS.  DEEPENING SURFACE LOW WILL BECOME
   CENTERED  OVER THE WESTERN DAKOTAS BY EARLY THIS EVENING...AND MAY
   BECOME FOCUS FOR HIGH BASED CONVECTIVE CLUSTER.  MEAN MIXED LAYER
   CAPE ON NOSE OF LOW-LEVEL THERMAL RIDGE ACROSS SOUTHWESTERN NORTH
   DAKOTA AND WESTERN SOUTH DAKOTA IS NOT PARTICULARLY STRONG...BUT
   DEEP MIXED BOUNDARY LAYER WITH LARGE TEMPERATURE/DEW POINT SPREADS
   WILL CONTRIBUTE TO POTENTIAL FOR DAMAGING WIND GUSTS.
   
   THIS ACTIVITY SHOULD DIMINISH WITH LOSS OF DAYTIME HEATING...BUT
   CONVECTION SHOULD INCREASING LATE THIS EVENING/OVERNIGHT...ALONG/
   NORTH OF SURFACE WARM FRONT...NEAR THE NORTH DAKOTA/MANITOBA BORDER.
    MODEL FORECAST SOUNDINGS SUGGEST CAPE FOR PARCELS LIFTED ABOVE
   LOW-LEVEL INVERSION LAYER ON THE ORDER OF 1000 TO 2000 J/KG. THIS
   WILL BE SUPPORTIVE OF VIGOROUS UPDRAFTS WITH POTENTIAL FOR LARGE
   HAIL IN FAVORABLY SHEARED ENVIRONMENT. STRONGER LOW-LEVEL WARM
   ADVECTION REGIME AND ASSOCIATED CONVECTION ON NOSE OF 30 TO 50 KT
   LOW-LEVEL JET WILL SPREAD EASTWARD INTO WESTERN ONTARIO AND EXTREME
   NORTHERN MINNESOTA OVERNIGHT.
   
   ..KERR.. 08/27/2003
   
   ...NOTICE...
   FOR USERS DECODING THE POINTS PARAGRAPH HEREIN...LATITUDE AND
   LONGITUDE POINTS FOR THE CATEGORICAL AND PROBABILISTIC OUTLOOK
   GRAPHICS ALSO ARE LOCATED IN A SEPARATE PRODUCT UNDER THE WMO
   HEADINGS WUUS01 PTSDY1...WUUS02 PTSDY2...AND WUUS03 PTSDY3.  THE
   INCLUSION OF POINTS IN THIS PRODUCT WILL EVENTUALLY BE DISCONTINUED.
   
   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED FOR 0100Z