SPC AC 181706
   
   DAY 2 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1206 PM CDT THU AUG 18 2005
   
   VALID 191200Z - 201200Z
   
   THERE IS A SLGT RISK OF SVR TSTMS TO THE RIGHT OF A LINE FROM 35 WNW
   SYR 15 S PSB 10 SW EKN 10 SSW CRW 45 WNW EMP 35 SSE RSL 50 SSW HSI
   30 S YKN 35 WNW RWF 35 NE STC 60 NNE EAU 25 SE MTW 35 NNW LAN 75 NNE
   MTC.
   
   GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM 20 WSW TPL 55 WNW LFK
   25 SSE SHV 15 NW MLU 25 SW GLH 50 NE PBF 45 S UNO 25 SSW UMN 30 SW
   OKC 20 S LTS 50 ENE BGS 25 W SJT 40 NNE JCT 20 WSW TPL.
   
   GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM 30 N PBG 15 SE GFL 30
   SW POU 15 WNW NEL 35 SSE NEL ...CONT... 25 SE SAN 30 N SBA 30 NW BFL
   45 ESE BIH 30 NE TPH 35 WNW ELY 50 E MLD 25 SSW JAC 25 NW BZN 40 E
   HLN 20 W LWT 65 NE 4BQ 60 SE BIS 35 SE JMS 20 SSE GFK 80 N GFK.
   
   ...THERE IS A SLGT RISK OF SVR TSTMS FROM THE MID MO VALLEY EWD
   ACROSS THE OH VALLEY...
   
   ...SYNOPSIS...
   AMPLIFIED YET PROGRESSIVE WAVE TRAIN ACROSS NRN TIER OF STATES IS
   EXPECTED TO CONTRIBUTE TO AN ACTIVE SEVERE WEATHER PERIOD
   FRIDAY/FRIDAY NIGHT.  MORE SPECIFICALLY...SHORTWAVE TROUGH CURRENTLY
   OVER THE UPPER MS VALLEY/WRN GREAT LAKES IS FORECAST TO LOSE
   AMPLITUDE AS IT PROGRESSES ENEWD FROM THE CNTRL GREAT LAKES THROUGH
   THE ST. LAWRENCE VALLEY.  MEANWHILE...VIGOROUS UPSTREAM SYSTEM /NOW
   OVER AB/SK/ WILL TRANSLATE SEWD ACROSS THE NRN PLAINS AND INTO THE
   WRN GREAT LAKES BY 20/12Z. WITHIN THIS LARGER-SCALE PATTERN...AN
   AXIS OF MODERATE TO STRONG MID-LEVEL FLOW /I.E. 35-45 KTS AT 500 MB
   OVER THE OH VALLEY...INCREASING TO 60-70 KTS OVER THE NRN PLAINS/
   WILL PERSIST FROM THE NRN PLAINS EWD ACROSS THE OH VALLEY.
   
   IN THE LOW-LEVELS...SURFACE CYCLONE ASSOCIATED WITH LEAD DISTURBANCE
   WILL DEVELOP FROM WRN LOWER MI NEWD INTO SWRN QC WITH ATTENDANT WARM
   FRONT ALSO LIFTING NEWD ACROSS THE CNTRL/UPPER OH VALLEY EWD ACROSS
   WRN/CNTRL NY/PA. A TRAILING...WEAK BOUNDARY WILL LIKELY EXTEND WWD
   ACROSS THE OH VALLEY TO SECONDARY LOW PRESSURE OVER THE UPPER
   MIDWEST. PRIMARY FEATURE...HOWEVER...WILL BE STRONG COLD FRONT WHICH
   WILL PUSH SEWD THROUGH THE NRN PLAINS FRIDAY...AND INTO THE WRN
   GREAT LAKES...UPPER MIDWEST AND CNTRL PLAINS FRIDAY NIGHT.
   
   ...UPPER OH VALLEY EWD INTO WRN NY/PA...
   CLUSTERS OF TSTMS WILL LIKELY BE ONGOING INITIALLY WITHIN LOW-LEVEL
   WAA REGIME ALONG/N OF RETREATING WARM FRONT FROM LOWER MI SWD ACROSS
   OH AND PERHAPS ERN KY/WV. FORCING FOR ASCENT ALONG SRN PERIPHERY OF
   LEAD SHORTWAVE TROUGH MOVING INTO THE ST. LAWRENCE VALLEY COUPLED
   WITH INFLUX OF MOIST LOW-LEVEL AIR MASS ALONG WSWLY LLJ IS EXPECTED
   TO SUSTAIN THIS ACTIVITY THROUGH THE DAY ACROSS THE UPPER OH VALLEY
   INTO WRN NY/PA.
   
   WHILE LOW-LEVEL CONVERGENCE IS FORECAST TO DECREASE IN WAKE OF WARM
   FRONTAL PASSAGE...RESIDUAL OUTFLOW BOUNDARIES AND TRAILING...WEAK
   CONFLUENCE ZONE MAY SERVE AS A FOCUS FOR ADDITIONAL STORM
   DEVELOPMENT FRIDAY AFTERNOON OVER PORTIONS OF IND/OH. GIVEN
   ANTICIPATED MODERATE INSTABILITY AND VERTICAL SHEAR...POTENTIAL WILL
   EXIST FOR SUPERCELLS AND/OR BOWING STRUCTURES IN BOTH OF THE
   AFOREMENTIONED CONVECTIVE REGIMES. THOUGH A TORNADO OR TWO IS
   POSSIBLE...IT APPEARS THAT DAMAGING WINDS AND MARGINALLY SEVERE HAIL
   WILL BE THE PRIMARY SEVERE WEATHER THREATS.
   
   ...MID MO VALLEY/UPPER MIDWEST INTO THE LOWER/MID OH VALLEY...
   POTENTIALLY MORE EXPLOSIVE SEVERE TSTM DEVELOPMENT IS ANTICIPATED
   FRIDAY AFTERNOON AND EVENING OVER DISCUSSION AREA IN ADVANCE OF
   STRONG MID-LEVEL TROUGH AND ASSOCIATED 60-70 KT MID-LEVEL JET
   STREAK. MOIST BOUNDARY-LAYER CONDITIONS /DEWPOINTS IN THE LOW-MID
   70S/ IN CONJUNCTION WITH STEEPENING MID-LEVEL LAPSE RATES ARE
   EXPECTED TO CONTRIBUTE TO MLCAPES INCREASING TO AOA 3000-3500 J/KG.
   MOREOVER...VERTICAL SHEAR WILL CONCURRENTLY INCREASE WITH APPROACH
   OF MID-LEVEL SPEED MAXIMUM WITH 40-50 KTS OF EFFECTIVE BULK SHEAR
   FORECAST ACROSS INSTABILITY AXIS DURING TIME OF PEAK HEATING.
   
   THIS COMBINATION OF SHEAR AND INSTABILITY SHOULD SUPPORT RAPID
   SEVERE STORM DEVELOPMENT BY MID/LATE AFTERNOON ALONG COLD FRONT FROM
   SRN MN ACROSS IA INTO ERN NEB. INITIALLY...SUPERCELLS CAPABLE OF
   LARGE HAIL...DAMAGING WINDS AND ISOLATED TORNADOES WILL BE LIKELY.
   WITH TIME...UPSCALE GROWTH INTO ONE OR MORE MCS/S WILL OCCUR WITH
   LARGE-SCALE ENVIRONMENT SUPPORTING EMBEDDED BOW ECHOES WITH
   POTENTIAL FOR WIDESPREAD DAMAGING WIND SWATHS SPREADING EWD ACROSS
   THE LOWER AND PERHAPS MID OH VALLEY FRIDAY NIGHT.
   
   ..MEAD.. 08/18/2005
   
   ...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 0800Z