SPC AC 201258
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0758 AM CDT TUE APR 20 2004
   
   VALID 201300Z - 211200Z
   
   THERE IS A SLGT RISK OF SVR TSTMS TO THE RIGHT OF A LINE FROM 40 SSW
   DEC 15 N MDH 25 E ARG 40 NNE LIT 30 E PRX 30 NE DAL 40 SSE SPS 30 SE
   OKC 30 SSW ICT 25 N HUT 15 ENE CNK 60 WSW YKN YKN 40 ENE SUX 60 WSW
   FOD 20 NNW BRL 25 S PIA 40 SSW DEC.
   
   GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM 20 N HSE 35 W SOP 50
   SE LOZ 30 W HOP 50 NE PBF 15 SSE GGG 30 N CLL 15 NNW AUS 55 W AUS 15
   E JCT 45 E SJT 40 SSW ABI 55 SSW SPS 25 NE FSI 45 SSW END 20 S P28
   40 NNE DDC 35 ENE AKO 15 NNW DEN 20 S GUC 40 NNE 4BL 50 WNW 4HV 55
   SE ELY 50 NE TPH 55 WNW TPH 20 WSW NFL 40 ENE SVE 4LW 65 SSW PDT 40
   W PUW 35 WNW S06 10 SE FCA 25 WNW HVR 25 N SDY 25 NW P24 30 E MOT 65
   NNW DVL ...CONT... 40 W RRT 35 WSW FAR 50 WSW AXN 50 NE MSP 35 SSW
   CMX ...CONT... 20 ENE ERI 40 ESE PSB 25 S ACY.
   
   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS ERN PORTIONS OF
   CENTRAL/SRN PLAINS EWD TO LOWER MO/MID MS VALLEYS...
   
   ...SYNOPSIS...
   STRONG WLY WINDS ALOFT OVER THE ERN PACIFIC WILL MOVE INLAND ACROSS
   THE GREAT BASIN TO SRN ROCKIES TODAY CARVING OUT A BROAD CYCLONIC
   FLOW REGIME ACROSS MUCH OF THE COUNTRY.  WEAK SHORT WAVE TROUGH WILL
   MOVE ENEWD ALONG THE OH VALLEY AS A STRONGER TROUGH...CURRENTLY
   LOCATED OVER THE CENTRAL/SRN PLAINS DEAMPLIFIES AS IT TRACKS NEWD
   TOWARD THE OH VALLEY/GREAT LAKES REGION.  UPSTREAM TROUGH...
   CURRENTLY LOCATED OVER THE INTERMOUNTAIN WEST WILL MOVE EWD REACHING
   THE CENTRAL/SRN PLAINS BY 00Z...AND TO THE MID/UPPER MS VALLEY BY
   12Z WEDNESDAY.
   
   12Z SURFACE ANALYSIS SHOWED AN ELONGATED SURFACE TROUGH WITH
   EMBEDDED SURFACE LOWS OVER WRN SD AND SWRN KS. A SURFACE BOUNDARY
   EXTENDED FROM ERN NEB ESEWD ACROSS NRN MO TO NEAR STL...AND THEN EWD
   THROUGH NRN KY TO DELMARVA REGION.  AN OUTFLOW BOUNDARY ASSOCIATED
   WITH ONGOING MCS OVER ERN KS EXTENDED GENERALLY E-W ACROSS FAR NRN
   OK INTO SWRN KS WHERE IT INTERSECTED A DRY LINE/LEE TROUGH EXTENDING
   FROM WRN KS SSWWD THROUGH THE WRN TX PANHANDLE TO SERN NM.  AS THE
   UPSTREAM TROUGH APPROACHES THE PLAINS...PRIMARY SURFACE LOW WILL
   MOVE EWD TO ERN NEB/WRN IA BY 00Z...BEFORE MOVING NEWD TO WI
   OVERNIGHT.  DRY LINE/COLD FRONT IS EXPECTED TO MOVE EWD ACROSS
   KS/WRN OK...AND SHOULD EXTEND FROM SERN NEB SSWWD TO ICT-OKC-MWL
   LINE BY 00Z.
   
   ...ERN PORTION OF THE CENTRAL/SRN PLAINS EWD TO MID MS VALLEY...
   SUBSIDENCE/DECREASING CLOUDS IN THE WAKE OF THE CENTRAL/SRN PLAINS
   SHORT WAVE TROUGH IS EXPECTED TO ALLOW FOR SUFFICIENT SURFACE
   HEATING ACROSS KS/OK TODAY.  WARM SECTOR WILL DESTABILIZE THROUGH
   THE DAY AS SSWLY 35-45 KT LLJ EXTENDING FROM ERN TX TO IL WILL
   RESULT IN STRONG MOISTURE ADVECTION NNEWD WITH SURFACE DEWPOINTS IN
   THE UPPER 50S REACHING IL AND LOWER 60S DEWPOINTS AS FAR NORTH AS
   SRN IA.  SURFACE TEMPERATURES IN THE MID 70S ACROSS ERN KS TO LOWER
   80 OVER SRN OK/NRN TX COMBINED WITH THE LOW-LEVEL MOISTURE AND
   STEEPENING LOW-MID LEVEL LAPSE RATES BY LATE THIS AFTERNOON WILL
   RESULT IN MODERATE INSTABILITY /MLCAPE 1000-2000 J/KG/ ACROSS ERN
   KS/OK INTO MO/NWRN AR. THUNDERSTORMS ARE EXPECTED TO DEVELOP MAINLY
   BETWEEN 21-00Z AS LARGE SCALE ASCENT BEGINS TO INCREASE ALONG THE
   DRY LINE.  ACTIVITY SHOULD INITIALLY DEVELOP OVER ERN KS WITH
   ADDITIONAL STORMS DEVELOPING SWD ACROSS ERN OK TO NRN-NERN TX TOWARD
   00-03Z ALONG THE DRY LINE...AND ALONG REMNANT OUTFLOW BOUNDARY ALONG
   KS/OK BORDER.  MODERATE INSTABILITY COMBINED WITH 35-40 KT DEEP
   LAYER SHEAR VECTORS CROSSING THE DRY LINE WILL SUPPORT DISCRETE
   SUPERCELLS WITH LARGE HAIL/DAMAGING WINDS AND ISOLATED TORNADOES
   EXPECTED.  THUNDERSTORMS WILL MOVE INTO MO/NWRN AR THIS EVENING WITH
   THE SEVERE THREAT TRANSITIONING INTO MORE OF A WIND THREAT AS SHEAR
   VECTORS BECOME ORIENTED MORE PARALLEL TO THE SURFACE FRONT.
   
   ...ERN NEB/WRN-SRN IA...
   CLOUDINESS ASSOCIATED WITH ONGOING THUNDERSTORMS OVER ERN NEB/SWRN
   IA IS EXPECTED TO MOVE EWD OF THIS REGION BY EARLY AFTERNOON
   ALLOWING FOR SOME SURFACE HEATING.  THIS COMBINED WITH STEEP LAPSE
   RATES AND SURFACE DEWPOINTS IN THE LOWER-MID 50S SHOULD RESULT IN
   MARGINAL INSTABILITY.  LOW-LEVEL CONVERGENCE IN THE VICINITY OF THE
   SURFACE LOW AND INVERTED TROUGH IS EXPECTED TO RESULT IN
   THUNDERSTORM DEVELOPMENT BY LATE AFTERNOON ACROSS FAR ERN NEB...
   WITH ACTIVITY SPREADING INTO WRN IA.  DESPITE MARGINAL
   INSTABILITY...SUFFICIENT DEEP LAYER SHEAR IS EXPECTED TO SUPPORT A
   SEVERE THREAT. ACTIVITY SHOULD WEAKEN THIS EVENING WITH THE LOSS OF
   DAY TIME HEATING STABILIZING THE AIR MASS.
   
   ...UPPER OH VALLEY...
   CLOUDINESS SPREADING EWD ACROSS THE OH VALLEY IS EXPECTED TO LIMIT
   SURFACE HEATING TODAY. HOWEVER...MODELS SUGGEST MARGINAL
   INSTABILITY MAY DEVELOP ACROSS SRN OH/ERN KY AND MUCH OF WV BY 18Z
   AS A MID-LEVEL THERMAL TROUGH ASSOCIATED WITH WEAK LEAD SHORT WAVE
   TROUGH MOVES ACROSS THIS REGION.  WEAK UPPER FORCING SHOULD SUPPORT
   AN AREA OF THUNDERSTORMS BY EARLY AFTERNOON...BUT WEAK INSTABILITY/
   SHEAR VALUES SHOULD LIMIT THE SEVERE POTENTIAL.
   
   ..PETERS/CROSBIE.. 04/20/2004
   
   ...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