SPC AC 230557
   
   DAY 2 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1257 AM CDT TUE AUG 23 2005
   
   VALID 241200Z - 251200Z
   
   THERE IS A SLGT RISK OF SVR TSTMS TO THE RIGHT OF A LINE FROM MCK
   HSI BIE MKC JLN BVO P28 45 W HLC MCK.
   
   THERE IS A SLGT RISK OF SVR TSTMS TO THE RIGHT OF A LINE FROM 80 NNW
   GFK GFK ABR PIR REJ MLS 70 NW ISN.
   
   GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM 10 WSW CZZ RAL 10 NE
   DAG P38 10 E ENV 15 SW PIH 15 SW PUW 35 NNW GEG 25 N 63S ...CONT...
   40 E RRT 10 W AXN 10 SE FRM COU 10 S TBN POF BNA 10 SE AND CAE FLO
   35 ESE ECG ...CONT... DRT TPL FTW 10 WNW CDS PVW HOB 45 SE ELP.
   
   ...THERE IS A SLGT RISK OF SVR TSTMS WED/WED EVENING ACROSS PARTS OF
   THE NRN PLAINS....
   
   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE CENTRAL
   PLAINS....
   
   AMPLIFIED SOUTHERN BRANCH OF POLAR JET WILL PERSIST ACROSS SOUTHERN
   CANADA AND THE NORTHERN TIER OF THE U.S. THROUGH THIS FORECAST
   PERIOD.  PROGRESSIVENESS OF EMBEDDED PERTURBATIONS...INCLUDING
   CLOSED LOW IN THE VICINITY OF THE NORTH ATLANTIC COAST...AND ANOTHER
   EVOLVING CLOSED LOW OVER THE NORTHERN ROCKIES...REMAINS A SOURCE OF
   CONSIDERABLE UNCERTAINTY. 
   
   EASTERN LOW NOW APPEARS TO BE GENERALLY CUT-OFF...BUT BY
   WEDNESDAY...LATEST NAM/GFS AND ENSEMBLES SUGGEST THAT THIS
   FEATURE...AND TRAILING TROUGH AXIS...WILL FINALLY BEGIN TO BE FORCED
   EAST OF ATLANTIC COASTAL AREAS.  UPSTREAM LOW IS FORECAST TO
   GRADUALLY DEVELOP NORTHEASTWARD INTO SASKATCHEWAN...WITH A COUPLE OF
   IMPULSES ROTATING AROUND ITS SOUTHERN/EASTERN PERIPHERY...ACROSS THE
   NORTH CENTRAL ROCKIES AND NORTHERN U.S. PLAINS.  THIS WILL OCCUR AS
   ANOTHER TROUGH DIGS TOWARD THE BRITISH COLUMBIA COAST.
   
   FARTHER SOUTH...MODELS SUGGEST SUBTROPICAL RIDGING...CENTERED OVER
   THE WESTERN/CENTRAL GULF STATES...WILL BEGIN TO EXPAND ONCE AGAIN. 
   SERIES OF WAVES ROTATING AROUND ITS PERIPHERY LIKELY WILL CONTRIBUTE
   TO CONVECTIVE DEVELOPMENT WEDNESDAY/WEDNESDAY NIGHT ACROSS PARTS OF
   THE FOUR CORNERS REGION...AND THE CENTRAL PLAINS.
   
   ...NORTHERN PLAINS...
   ALTHOUGH SURFACE BOUNDARY WILL LINGER OVER PORTIONS OF THE SOUTH
   CENTRAL PLAINS INTO WEDNESDAY...MOIST EAST SOUTHEASTERLY UPSLOPE
   FLOW REGIME IS ALREADY DEVELOPING ACROSS THE CENTRAL PLAINS...WHERE
   DEW POINTS ARE NOW NEAR 70F.  THIS MOISTURE SEEMS MORE THAN LIKELY
   TO ADVECT INTO THE NORTHERN PLAINS BY WEDNESDAY AFTERNOON...AS
   SOUTHERLY FLOW STRENGTHENS EAST OF LEE SURFACE TROUGH.
   
   PRIMARY SURFACE LOW IS PROGGED TO DEVELOP ACROSS SOUTHERN
   SASKATCHEWAN WEDNESDAY.  HOWEVER...TRAILING COLD FRONT MAY BECOME A
   FOCUS FOR CONVECTIVE DEVELOPMENT BY PEAK HEATING AS IT SURGES ACROSS
   EASTERN MONTANA INTO WESTERN NORTH DAKOTA.  FRONT WILL GRADUALLY
   MERGE WITH PRE-FRONTAL TROUGH AXIS...ALONG WHICH STRONG HEATING OF
   BOUNDARY LAYER IS EXPECTED TO CONTRIBUTE TO CAPE IN EXCESS OF 2000
   J/KG.
   
   STRENGTH OF CAPPING ASSOCIATED WITH MID-LEVEL THERMAL RIDGE IS A
   CONCERN...PARTICULARLY TO THE SOUTH/EAST OF THERMAL LOW FORMING OVER
   WESTERN SOUTH DAKOTA.  HOWEVER...STRONGLY DIFLUENT AND DIVERGENT
   UPPER FLOW FIELD OVERSPREADING NORTH DAKOTA BY LATE WEDNESDAY
   AFTERNOON IS EXPECTED TO CONTRIBUTE TO MID-LEVEL UPWARD VERTICAL
   MOTION...WEAKENING CAP AND SUPPORTING CONVECTIVE DEVELOPMENT.
   
   SHEAR WILL BE MARGINALLY SUFFICIENT FOR SUPERCELLS IN INITIAL
   ACTIVITY.  BUT...CONVECTIVE CLUSTER IS EXPECTED TO EVOLVE IN
   ENVIRONMENT WHERE DRY MID-LEVELS WITH STEEP LAPSE RATES WILL
   CONTRIBUTE TO SOUNDINGS SUPPORTIVE OF ISOLATED VERY LARGE HAIL AND
   DAMAGING DOWNBURSTS.  SEVERE THREAT SHOULD CONTINUE/SLOWLY DEVELOP
   SOUTHWARD WELL INTO THE EVENING HOURS...BEFORE STABILIZING BOUNDARY
   LAYER WEAKENS STORMS OVERNIGHT.
   
   ...CENTRAL PLAINS...
   MODELS SUGGEST CAPPING IN WAKE OF MID-LEVEL IMPULSE ASSOCIATED WITH
   SUBTROPICAL STREAM MAY BE SLOW TO STRENGTHEN OVER CENTRAL KANSAS
   WEDNESDAY.  THIS IS WHERE SOUTHERLY LOW-LEVEL JET IS FORECAST TO
   FOCUS WARM ADVECTION ALONG/NORTH OF LINGERING SURFACE FRONT.  VERY
   MOIST BOUNDARY LAYER WITH DEW POINTS AROUND 70F WILL BECOME MODERATE
   TO STRONGLY UNSTABLE BY PEAK AFTERNOON HEATING... AND CAPE IN EXCESS
   OF 3000 J/KG APPEARS POSSIBLE. THOUGH NOT STRONG...WESTERLY
   COMPONENT TO MID-LEVEL FLOW IS EXPECTED TO CONTRIBUTE TO SUFFICIENT
   SHEAR FOR A FEW SUPERCELLS...WITH LARGE HAIL/DAMAGING
   WINDS...POSSIBLY ISOLATED TORNADOES.
   
   ENTRANCE REGION OF INCREASINGLY ANTICYCLONIC HIGH-LEVEL JET STREAK
   MAY SUPPORT EVOLUTION OF LARGE CONVECTIVE CLUSTER BY WEDNESDAY
   EVENING.  ACTIVITY SHOULD SPREAD EAST NORTHEASTWARD TOWARD THE
   MISSOURI VALLEY...AND MAY BE ACCOMPANIED BY STRONG GUSTY WINDS ALONG
   OUTFLOWS...BEFORE LOCALLY HEAVY RAIN BECOMES PRIMARY THREAT
   OVERNIGHT.
   
   ...GULF STATES...
   VERY MOIST AIR MASS WILL PERSIST SOUTH OF SURFACE FRONT ASSOCIATED
   WITH EASTERN TROUGH.  SCATTERED CONVECTIVE DEVELOPMENT WILL OCCUR
   WITH DAYTIME HEATING...AND THERMODYNAMIC PROFILES BY PEAK HEATING
   MAY BECOME FAVORABLE FOR HIGHLY LOCALIZED DOWNBURSTS IN
   STRONGER...BUT GENERALLY SHORT-LIVED CELLS.
   
   ..KERR.. 08/23/2005
   
   ...NOTICE...
   THE STATION RELATIVE POINTS IN THIS PRODUCT ARE NOW AVAILABLE
   SEPARATELY UNDER THE WMO HEADINGS WUUS01 PTSDY1...
   WUUS02 PTSDY2...WUUS03 PTSDY3.  THE INCLUSION OF POINTS
   IN THIS DISCUSSION WILL BE DISCONTINUED AFTER THE 2005
   CONVECTIVE SEASON.  A PUBLIC NOTIFICATION STATEMENT (PNS)
   WILL PROVIDE DETAILS ON THE TRANSITION.
   
   CLICK TO GET WUUS02 PTSDY2 PRODUCT

   NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 1730Z