SPC AC 170556
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1256 AM CDT SAT APR 17 2004
   
   VALID 171200Z - 181200Z
   
   THERE IS A SLGT RISK OF SVR TSTMS TO THE RIGHT OF A LINE FROM 15 WSW
   BUF 30 ENE FKL PIT HLG UNI DAY CGX RFD CID DSM OMA OFK YKN BKX STC
   IMT ESC APN.
   
   GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM 20 W DUG 80 NW TCS
   GUP 55 SW CEZ GCN 45 SSE IGM 30 ESE TRM 30 NNW SAN PRB 35 E UKI 20
   NW MHS 75 N 4LW BKE 3TH 80 NW FCA ...CONT... 30 ENE PWM ABE 25 NNW
   EKN HTS SDF 25 NW EVV 10 E ALN IRK 25 SW P35 EMP 35 E CSM ABI 20 SE
   DRT.
   
   ...THERE IS A SLGT RISK OF SVR TSTMS SERN SD/NERN NEB EWD ACROSS
   CENTRAL/SRN GREAT LAKES REGION...
   
   ...SYNOPSIS...
   UPPER AIR PATTERN DURING PERIOD WILL BE DOMINATED BY PROGRESSIVE WRN
   TROUGH -- NOW OVER PACIFIC COAST AND PROGGED TO MOVE INLAND THROUGH
   PERIOD.  SHORTWAVE PERTURBATION WILL EJECT NEWD FROM BASE OF LARGER
   SCALE TROUGH...REACHING INVOF 4-CORNERS REGION BY 18/12Z.  AS THIS
   OCCURS...INTENSE LOW LEVEL WAA REGIME WILL CONTINUE ACROSS MUCH OF
   CENTRAL CONUS...WITH CONTINUING NET NNEWD TRANSPORT OF MOISTURE FROM
   MODIFYING GULF AIR MASS.
   
   AT SFC...WAVY FRONTAL ZONE -- NOW OVER SERN ONT...LOWER MI AND
   PORTIONS IA/ERN NEB/NRN KS...IS EXPECTED TO SAG SWD ACROSS GREAT
   LAKES REGION.  FARTHER W OVER UPPER MS VALLEY...IA AND
   NEB...BAROCLINIC ZONE SHOULD LIFT NWD AS WARM FRONT IN RESPONSE TO
   CYCLOGENESIS ACROSS CENTRAL HIGH PLAINS.  POSITION OF FRONT OVER
   IA/WI/IL THROUGH MUCH OF DAY MAY BE SHUNTED FARTHER S THAN MODEL
   GUIDANCE BY OUTFLOW POOL PRODUCED BY MCS THAT IS MOVING ACROSS UPPER
   MS VALLEY AS OF THIS WRITING.  DURING 21Z-00Z TIME FRAME EXPECT
   DRYLINE FROM S-CENTRAL NEB SSWWD ACROSS DDC REGION TO NEAR
   CVS...THEN SWD ACROSS ERN NM INTO BIG BEND AREA OF W TX.
   
   ...UPPER MIDWEST...UPPER MS VALLEY...
   SEVERE TSTMS MAY DEVELOP MID-LATE AFTERNOON INTO EVENING...INVOF SFC
   WARM FRONT...ESPECIALLY BETWEEN NERN NEB/SERN SD AND MS RIVER. 
   SUPERCELLS AND BOW MODES ARE POSSIBLE.
   
   SEVERAL DAYS PRIOR OF PERSISTENT SWLY LOW-MIDLEVEL FLOW WILL RESULT
   IN SUBSTANTIAL CAPPING OVER MOST OF REGION...THEREFORE SEVERE
   PROBABILITIES S OF BAROCLINIC ZONE ARE QUITE CONDITIONAL.  CAPPING
   ALSO SHOULD LIMIT COVERAGE OF SFC-BASED DEVELOPMENT ALONG FRONT AND
   RESULT IN LATE AFTERNOON INTO EARLY EVENING INITIATIONS.  FRONTAL
   FORCING COMBINED WITH STRONG DIABATIC HEATING SHOULD BE SUFFICIENT
   FOR SOME SEVERE POTENTIAL BEFORE DARK. THOUGH LITTLE OR NO
   ADDITIONAL MID-UPPER LEVEL DESTABILIZATION IS ANTICIPATED WITH
   SHORTWAVE RIDGING ALOFT...LAPSE RATES ALREADY ARE STEEP ACROSS
   REGION BECAUSE OF ADVECTION OF ELEVATED MIXED-LAYER AIR MASS.  MID
   50S TO NEAR 60 F SFC DEW POINTS SHOULD CONTRIBUTE TO MLCAPE IN
   2000-2500 J/KG RANGE...BENEATH STEEP MIDLEVEL LAPSE RATES OF 8-9 DEG
   C/KM.
   
   MCS SHOULD DEVELOP N OF SFC FRONT AFTER DARK -- PERHAPS EVOLVING
   FROM LATE AFTERNOON CONVECTION.  ACTIVITY SHOULD MOVE EWD-NEWD
   ACROSS REGION WHERE AIR MASS JUST LEFT OF LLJ NOSE WILL BENEFIT FROM
   ELEVATED MUCAPE 1000-1500 J/KG...ASSOCIATED WITH GRADUALLY
   INCREASING LOW LEVEL MOISTURE AND ISENTROPIC ASCENT OF PARCELS TO
   LFC.
   
   ...SRN GREAT LAKES...OH VALLEY...
   TSTMS MAY DEVELOP DURING 18Z-21Z TIME FRAME IN A SEPARATE ERN LOBE
   -- ACROSS PORTIONS NRN INDIANA/SRN LOWER MI...THEN CONGEAL INTO ONE
   OR TWO EWD-SEWD MOVING CLUSTERS PRODUCING HAIL AND POTENTIALLY
   DAMAGING WIND. THIS ACTIVITY WILL BE STRONGLY DIURNAL AND SHOULD
   WEAKEN SUBSTANTIALLY AFTER SUNSET.
   
   WITH LESS ELEVATED MIXED-LAYER AIR OVER THIS REGION THAN FARTHER
   W...AIR MASS WILL BE MORE WEAKLY CAPPED...SUPPORTING BOTH CONVECTIVE
   INITIATION INVOF FRONTAL ZONE AND MOTION OF ACTIVITY OFF IT.  MODEL
   SOUNDINGS SHOW FAVORABLE VERTICAL SHEAR PROFILES FOR ORGANIZED
   MULTICELLS AND MARGINAL SUPERCELLS.  MAIN CONCERN IS LACK OF RICH
   BOUNDARY LAYER MOISTURE...WHICH APPEARS TO CONTRIBUTE TO PROBABLE
   OVERFORECAST OF SBCAPE IN ETA. HOWEVER...HIGHER CLOUD BASES AND
   WELL MIXED BOUNDARY LAYERS SHOULD SUPPORT STRONG-SEVERE DOWNDRAFTS.
   
   ...CENTRAL/SRN PLAINS...
   MARGINAL/CONDITIONAL SEVERE PROBABILITIES EXTEND SSWWD FROM SFC
   FRONT ALONG DRYLINE.  EXPECT STRONG CAPPING TO GREATLY RESTRICT TSTM
   DEVELOPMENT ALONG MOST OF DRYLINE.  HOWEVER...ISOLATED CONVECTION
   MAY INITIATE DURING LATE AFTERNOON.  VIGOROUS SFC HEATING AND 50S TO
   LOW 60S SFC DEW POINTS IN ADJACENT MOIST SECTOR SHOULD CONTRIBUTE TO
   MLCAPE 500-1500 J/KG WITH HIGH LCL.  ANY TSTMS THAT DO DEVELOP
   SHOULD BE SHORT-LIVED AND HIGH-BASED...WITH BRIEF POTENTIAL FOR HAIL
   AND STRONG-SEVERE GUSTS.
   
   ..EDWARDS/GUYER.. 04/17/2004
   
   ...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 1300Z