SPC AC 180542
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1242 AM CDT SAT SEP 18 2004
   
   VALID 181200Z - 191200Z
   
   GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM 50 NE HVR 45 NNE BIL
   50 ESE WEY 35 S LND 30 NE CAG 20 W ASE 50 NE DRO 40 W TAD 35 NW CAO
   40 ENE ROW 60 WNW MRF.
   
   GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM 50 NW DRT 25 NNW JCT
   30 SSW FTW 65 WNW LFK 25 NE HOU GLS.
   
   GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM 20 W CZZ 30 NE RAL 30
   N DAG 60 S EKO 30 SSE BYI 60 NE BOI 65 WSW BNO 60 NW UKI.
   
   GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM 25 N PIE 15 SE DAB.
   
   GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM 30 SE EWN 10 ENE GSB
   45 SE LYH 25 WNW BWI 25 SE AVP BOS.
   
   GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM 45 NNW ELO 15 SE HIB
   35 ESE BJI 55 SW DVL 70 NE MOT.
   
   GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM 20 NNW EMP 30 W BIE
   OFK 15 NW SUX 25 S FRM 25 ESE MSP 55 NE EAU 35 E AUW 30 SW PIA 40
   SSW STL 35 WNW UNO 35 S UMN 20 SSW CNU 20 NNW EMP.
   
   ...NO SVR TSTM AREAS FORECAST...
   
   LATEST SATELLITE IMAGERY SUPPORTS MODEL PROGS INDICATING
   AMPLIFICATION OF UPPER FLOW PATTERN WILL CONTINUE THROUGH THIS
   FORECAST PERIOD.  INITIAL SIGNIFICANT SHORT WAVE TROUGH...NOW ALONG
   THE PACIFIC NORTHWEST COAST...WILL LIFT ACROSS THE NORTHERN ROCKIES
   TODAY...AS ANOTHER STRONG UPPER JET STREAK DIGS OFF THE PACIFIC
   COAST. DOWNSTREAM OF SHARPENING LARGE-SCALE TROUGH AXIS ALONG THE
   PACIFIC COAST...UPPER RIDGE OVER THE PLAINS IS FORECAST TO BUILD
   NORTHWARD/SHIFT SLOWLY EASTWARD...AND EXTEND ALONG AN AXIS FROM THE
   RIO GRANDE VALLEY INTO ONTARIO BY SATURDAY NIGHT.  FARTHER
   EAST...MEAN TROUGH AXIS ASSOCIATED WITH POLAR/SUBTROPICAL SHORT
   WAVES WILL SLOWLY SHIFT INTO THE VICINITY OF THE ATLANTIC COAST.
   
   ...MID ATLANTIC COAST STATES...
   FRONTAL ZONE ACROSS SOUTHERN NEW ENGLAND INTO THE NORTHERN MID
   ATLANTIC COAST AREAS...AND WEAKENING/ELONGATING CIRCULATION
   ASSOCIATED WITH REMNANTS OF IVAN...WILL STILL PROVIDE FOCUS FOR
   CONVECTIVE DEVELOPMENT TODAY.  BOUNDARY LAYER WILL REMAIN VERY MOIST
   WITH DEW POINTS AROUND 70F EAST OF THESE FEATURES...AND SHOULD
   BECOME WEAK TO MODERATELY UNSTABLE WITH DAYTIME HEATING.  WITH
   STRONGER LOW-LEVEL FLOW FIELDS/SHEAR PROFILES ALREADY SHIFTING
   OFFSHORE...WARM THERMODYNAMIC PROFILES WITH WEAK LAPSE RATES ARE
   EXPECTED TO PRECLUDE SEVERE THREAT.  FRONTAL ZONE AND SURFACE LOW
   ARE PROGGED TO SHIFT OFFSHORE BY LATE AFTERNOON.  AS THIS OCCURS...
   CONVECTIVE POTENTIAL WILL DIMINISH.
   
   ...MID MISSOURI/UPPER MISSISSIPPI VALLEY AND PLAINS...
   CONVECTIVE CLUSTER LIKELY WILL BE ONGOING AT THE START OF THE
   FORECAST PERIOD ACROSS PARTS OF NORTHEAST KANSAS/NORTHERN MISSOURI. 
   HOWEVER...AS NOCTURNAL LOW-LEVEL JET WEAKENS AND BACKS IN RESPONSE
   TO EVOLVING UPSTREAM UPPER FLOW PATTERN...ACTIVITY IS EXPECTED TO
   SLOWLY DIMINISH BY THE 15-18Z TIME FRAME.
   
   THEREAFTER...CONVECTIVE POTENTIAL THROUGH THE REMAINDER OF THE
   FORECAST PERIOD ACROSS MUCH OF THE CENTRAL U.S. IS UNCERTAIN...
   PRIMARILY DUE TO STRENGTHENING INHIBITION BENEATH BUILDING UPPER
   RIDGE. ONE FOCUS FOR CONVECTIVE INITIATION COULD BE CONFLUENT BAND
   NEAR SOUTHERLY LOW-LEVEL JET AXIS ACROSS EASTERN NEBRASKA.  ETA
   POINT FORECAST SOUNDINGS SUGGEST LOW-LEVEL WARM ADVECTION AND STRONG
   HEATING MAY BECOME SUFFICIENT TO OVERCOME CAP BY LATE AFTERNOON.  AT
   LEAST AN ISOLATED STORM OR TWO APPEARS POSSIBLE...AND...IF THIS
   OCCURS...THERMODYNAMIC ENVIRONMENT WILL BE SUPPORTIVE OF SOME
   HAIL/ISOLATED DOWNBURSTS.
   
   WHILE LIMITED CONVECTIVE POTENTIAL ACROSS THE MID MISSOURI VALLEY
   DIMINISHES WITH LOSS OF HEATING...SCATTERED AREAS OF CONVECTION ALSO
   APPEAR POSSIBLE TONIGHT ALONG EASTERN PERIPHERY OF MID-LEVEL CAP
   ACROSS PARTS OF THE UPPER MISSISSIPPI VALLEY.  THIS WILL OCCUR AS
   STRONG SOUTHERLY LOW-LEVEL JET BEGINS TO VEER...PERHAPS AIDED BY
   FORCING ASSOCIATED WITH WEAK HIGH-LEVEL SHORT WAVE...WHICH IS NOW
   LIFTING FROM THE GREAT BASIN INTO THE CENTRAL ROCKIES. THIS SYSTEM
   IS PROGGED TO CONTINUE INTO CREST OF UPPER RIDGE BY LATE TONIGHT.
   
   FARTHER SOUTH...MOIST AND MUCH MORE WEAKLY CAPPED AIR MASS OVER
   CENTRAL/EASTERN TEXAS IS EXPECTED TO BECOME SUPPORTIVE OF A FEW
   THUNDERSTORMS DURING THE HOURS NEAR/SHORTLY AFTER PEAK HEATING.
   
   ...WESTERN STATES...
   INFLUX OF LOWER LATITUDE MID/HIGH-LEVEL MOISTURE IS PROGGED INTO THE
   SOUTHERN PLATEAU AND GREAT BASIN...AHEAD OF AMPLIFYING PACIFIC COAST
   TROUGH.  THIS WILL BE ACCOMPANIED BY INCREASING THUNDERSTORM
   ACTIVITY TODAY.  CONSIDERABLE CLOUD COVER MAY REDUCE SURFACE HEATING
   AND LIMIT BROADER SEVERE THREAT.  HOWEVER...ON WESTERN GRADIENT OF
   RETURNING MOISTURE...CONVECTIVE DESTABILIZATION MAY PROVE SUFFICIENT
   FOR VIGOROUS THUNDERSTORM ACTIVITY.  LOW/MID-LEVEL FLOW FIELDS/SHEAR
   PROFILES WILL GRADUALLY STRENGTHEN EASTWARD INTO THIS AREA DURING
   THE DAY...CONTRIBUTING TO AT LEAST SOME RISK FOR DAMAGING SURFACE
   GUSTS/MARGINAL SEVERE HAIL.
   
   ...FLORIDA PENINSULA...
   SOUTHEAST OF UPPER TROUGH/SHEAR AXIS ACROSS THE CENTRAL FLORIDA
   PENINSULA...THERMODYNAMIC ENVIRONMENT WILL REMAIN SUPPORTIVE OF 
   SCATTERED THUNDERSTORM ACTIVITY ALONG SEA BREEZES DURING THE
   AFTERNOON AND EARLY EVENING HOURS.
   
   ..KERR/JEWELL.. 09/18/2004
   
   ...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 1300Z