Sep-17-2004 1300 UTC Day 1 Convective Outlook
Updated: Fri Sep 17 12:53:45 UTC 2004
Categorical Graphic
20040917 1300 UTC Day 1 Outlook Graphic
Probablistic Tornado Graphic
20040917 1300 UTC Day 1 Tornado Probabilities Graphic
Probablistic Damaging Wind Graphic
20040917 1300 UTC Day 1 Damaging Wind Probabilities Graphic
Probablistic Large Hail Graphic
20040917 1300 UTC Day 1 Large Hail Probabilities Graphic
   SPC AC 171246
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0746 AM CDT FRI SEP 17 2004
   
   VALID 171300Z - 181200Z
   
   THERE IS A SLGT RISK OF SVR TSTMS TO THE RIGHT OF A LINE FROM 40 E
   TRI 20 ESE PSK CHO RIC 10 SSW GSB 35 S FLO CAE SPA 35 WNW HKY 40 E
   TRI.
   
   GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM 35 E INL 50 S DLH 30
   E RST 10 W IRK 35 WNW SGF 10 W MKO 40 ENE DAL 55 NNE CLL 20 SSE BPT
   ...CONT... 10 W ELP 40 WNW CVS 40 NNE CAO 45 NNW GLD 50 NE ANW 15 NW
   BKX 45 WNW AXN 65 W RRT.
   
   GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM 50 ENE CTB 30 W BTM
   25 N BOI 25 SSE CEC.
   
   GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM 15 S IPL 35 ENE TRM
   15 SW EED 30 SSE IGM 55 WSW SOW 30 NE SAD 35 SSW DMN.
   
   GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM 35 WSW PNS 25 NNE CEW
   20 ENE MGM 35 NNW BHM 50 WSW BNA 35 SW SDF 25 SSE CAK 35 WSW GFL 15
   ESE PWM.
   
   ...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS SC/VA/NC...
   
   ...SYNOPSIS...
   MID/UPPER LEVEL PATTERN THROUGH PERIOD IS EXPECTED TO BE
   CHARACTERIZED BY PROGRESSIVE NRN STREAM FROM PACIFIC NW TO NEW
   ENGLAND AND CANADIAN MARITIMES...WHILE UPPER RIDGING INTENSIFIES
   OVER SRN PLAINS.  HEIGHTS ARE FCST TO FALL OVER WA/ORE AS SHORTWAVE
   TROUGH -- NOW EVIDENT IN MOISTURE CHANNEL IMAGERY SW-NE OF VANCOUVER
   ISLAND -- SHOULD PIVOT ASHORE THIS EVENING ROUGHLY BETWEEN
   18/00Z-06Z.  MEANWHILE...SFC AND UPPER AIR REMAINS OF TC IVAN SHOULD
   MOVE NEWD OVER SRN APPALACHIANS REGION.  CENTER OF THIS CYCLONE
   SHOULD FINISH LINKING WITH SFC FRONTAL ZONE AND MOVE TO S-CENTRAL VA
   OR N-CENTRAL NC BY END OF PERIOD...WITH COLD FRONT SWWD TO WRN FL
   PANHANDLE AND NEWD ACROSS SRN/ERN NEW ENGLAND. WRN PORTION OF THIS
   FRONT IS RETREATING NWD ACROSS OK AND SW KS AS SUBTLE WARM FRONT. 
   SFC ANALYSIS SHOWS THIS FEATURE ALSO IS ACCOMPANIED BY PRONOUNCED
   SFC MOIST AXIS...WITH DEW POINTS LOW 60S TO LOW 70S F FROM SWRN KS
   SEWD ACROSS CENTRAL OK TO N-CENTRAL TX.
   
   ...NC/VA/SC...
   VERTICAL SHEAR WILL REMAIN FAVORABLE FOR SUPERCELLS AND RISK OF A
   FEW TORNADOES ACROSS MUCH OF REGION...ASSOCIATED WITH REMAINS OF
   IVAN.  0-1 KM SRH SHOULD REMAIN IN 150-300 J/KG RANGE...AS
   ISALLOBARIC FORCING ENE-ESE OF SFC LOW MAINTAINS SOME BACKING OF
   FLOW...HELPING TO ENHANCE SHEAR ESPECIALLY OVER PIEDMONT AREA AND
   WRN PORTIONS COASTAL PLAIN.  FARTHER E...VERTICAL SHEAR SHOULD
   DECREASE WITH DISTANCE FROM CYCLONE CENTER.  ALSO...KINEMATIC
   SUPPORT SHOULD DIMINISH WITH SWD EXTENT OVER GA AND NRN FL AS VEERED
   BOUNDARY LAYER FLOW REDUCES LOW LEVEL SHEAR AND CONVERGENCE. 
   TORNADO THREAT TENDENCY SHOULD BE STRONGLY DIURNAL TODAY BECAUSE OF
   THERMODYNAMIC SUPPORT. BROKEN CLOUD COVER WILL MODULATE DIURNAL
   INCREASE IN BUOYANCY ESPECIALLY NRN PORTIONS OUTLOOK AREA. 
   HOWEVER...MODIFIED RAOBS AND MODEL FCST SOUNDINGS SUGGEST MLCAPES
   1200-1700 J/KG ARE POSSIBLE WITH SFC INSOLATION AND DEW POINTS 70S F
   OVERCOMING WEAK DEEP-LAYER LAPSE RATES.  TORNADO POTENTIAL SHOULD
   GRADUALLY DIMINISH AGAIN THROUGH EVENING INTO TONIGHT AS RESULT OF
   SLOW DIABATIC SFC COOLING AND CONTINUED WEAKENING OF KINEMATIC
   FIELDS WITH IVAN CIRCULATION.
   
   ...CENTRAL PLAINS...
   NRN KS ONGOING/ELEVATED TSTMS SUPPORTED BY STRONG LOW LEVEL WAA
   PROFILE AND MARGINAL BUT INCREASING LOW LEVEL MOISTURE -- ABOVE
   RELATIVELY STABLE BOUNDARY LAYER.  ELEVATED MUCAPE IN 1000-2000 J/KG
   RANGE SUPPORTED BY 8-9 DEG C/KM MIDLEVEL LAPSE RATES WILL SUPPORT
   POTENTIAL FOR ISOLATED/MARGINAL SEVERE HAIL ANOTHER COUPLE HOURS
   UNTIL LLJ WEAKENS WITH DIMINISHED VERTICAL DECOUPLING OF BOUNDARY
   LAYER.
   
   ANOTHER ROUND OF TSTMS IS POSSIBLE THIS AFTERNOON INVOF SFC LOW AND
   TROUGH OVER PORTIONS WRN KS...PERHAPS NW OK ALSO...WITH ISOLATED
   DAMAGING GUSTS AND LARGE HAIL CONDITIONALLY POSSIBLE.  CONVECTIVE
   COVERAGE IN THIS AREA WILL BE LIMITED BY STRONG CAPPING...HOWEVER
   HEATING TO NEAR CONVECTIVE TEMPERATURE AND LIFT NEAR TROUGH SHOULD
   CONTRIBUTE TO SOME DEVELOPMENT LATE AFTERNOON. EXPECT STEEP LAPSE
   RATES ALOFT AND STRONG HEATING/MIXING THIS AFTERNOON...WITH HIGH
   CLOUD BASES BENEATH 500-1200 J/KG MLCAPE.  STRONG DIRECTIONAL SHEAR
   SHOULD CONTINUE...BUT WITH WEAK TO NEGATIVE 0-6 KM SPEED SHEAR. 
   CONVECTION SHOULD DIMINISH QUICKLY AFTER SUNSET AS DIABATIC COOLING
   ELIMINATES SBCAPE.
   
   ..EDWARDS/BANACOS.. 09/17/2004
   
   ...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 1630Z