SPC AC 211955
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0255 PM CDT WED APR 21 2004
   
   VALID 212000Z - 221200Z
   
   THERE IS A MDT RISK OF SVR TSTMS TO THE RIGHT OF A LINE FROM HRO 35
   NW LIT HOT 25 N TXK PRX ADM GAG 40 WSW P28 BVO UMN HRO.
   
   THERE IS A SLGT RISK OF SVR TSTMS TO THE RIGHT OF A LINE FROM MSS
   ELM IPT 20 SE CXY 10 SE MRB 50 ESE MGW LBE FKL CAK MFD FDY EVV POF
   35 S JBR 10 SE MEM 50 ESE MKL 15 ESE BWG 30 WNW LOZ 30 SE LOZ 30 SW
   HSV MLU SHV TYR FTW FSI 40 WSW GAG 30 NE DHT 15 SSE LAA 60 N GCK ICT
   TBN BLV MTO 10 W AZO 15 ESE APN.
   
   GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM 50 NNW HVR 10 W GDV
   MBG 10 SE ATY RWF FOD LWD COU DEC CGX 25 WSW MBL 50 ESE ANJ
   ...CONT... 40 ESE EWN 15 ESE RWI 35 NE LYH 15 W SSU 10 ESE RMG 20
   WNW LUL 25 WNW HOU 45 NW NIR 35 SSE JCT 40 NNW MWL 15 ESE LTS 35 WNW
   RTN FMN 40 WNW 4HV 35 NE U31 55 N SVE 30 S MFR 50 NNW 4BK.
   
   ...THERE IS A MDT RISK OF SVR TSTMS LATE THIS AFTN/EVE ACROSS MUCH
   OF NRN/ERN OK INTO WRN AR....
   
   ...THERE IS A SLGT RISK OF SVR TSTMS FROM THE SOUTHERN PLAINS INTO
   THE LOWER GREAT LAKES REGION....
   
   ...SOUTH CENTRAL PLAINS INTO LOWER MISSISSIPPI VALLEY...
   ENVIRONMENT HAS ALREADY BECOME MODERATELY UNSTABLE NEAR CONVECTIVELY
   ENHANCED LOW-LEVEL BAROCLINIC ZONE EXTENDING FROM SOUTHERN ARKANSAS
   WEST NORTHWESTWARD INTO THROUGH NORTH CENTRAL OKLAHOMA.  MEAN MIXED
   LAYER CAPE IS ALREADY IN EXCESS OF 1500 J/KG...AND MAY EXCEED 2000
   J/KG WITH FURTHER HEATING.  CAP IS CURRENTLY INHIBITING CONVECTIVE
   DEVELOPMENT...BUT FORCING ASSOCIATED WITH TIGHTENING LOW-LEVEL
   BAROCLINIC ZONE/STRENGTHENING LOW-LEVEL CONVERGENCE LIKELY WILL
   SUPPORT RAPID CONVECTIVE DEVELOPMENT DURING THE 21/21Z-22/00Z TIME
   FRAME. ACTIVITY WILL BE SUPPORTED BY FORCING ASSOCIATED WITH JET
   STREAK/SHORT WAVE TROUGH ALREADY MIGRATING EASTWARD OUT OF THE
   SOUTHERN HIGH PLAINS...AHEAD OF MUCH STRONGER UPPER JET DIGGING
   ACROSS THE NORTH CENTRAL PACIFIC COAST INTO THE GREAT BASIN.
   
   GIVEN STRONG VERTICAL SHEAR PROFILES ASSOCIATED WITH MID-LEVEL
   WESTERLIES...A FEW SUPERCELLS ARE LIKELY...WITH VERY LARGE HAIL/
   DAMAGING WIND GUSTS.  CLOSER TO/SHORTLY AFTER 22/00Z...MODELS
   SUGGEST SOUTHERLY LOW-LEVEL JET INTO BOUNDARY WILL STRENGTHEN...
   CONTRIBUTING TO INCREASINGLY FAVORABLE LOW-LEVEL HODOGRAPHS FOR
   TORNADIC SUPERCELLS.  GREATEST RISK GENERALLY APPEARS TO BE
   NEAR/NORTH THROUGH EAST OF THE OKLAHOMA CITY METROPOLITAN AREA...
   BEFORE FORCING ASSOCIATED WITH MID-LEVEL TROUGH SPREADS TOWARD THE
   OZARKS LATER THIS EVENING.  UPPER FORCING WILL SUPPORT EVENTUAL
   EVOLUTION OF LARGE MESOSCALE CONVECTIVE SYSTEM...WITH DAMAGING WINDS
   AN INCREASING THREAT EASTWARD INTO ARKANSAS OVERNIGHT.
   
   ...GREAT LAKES INTO MISSISSIPPI VALLEY...
   MID-LEVEL DRYING HAS ALLOWED SUFFICIENT SURFACE HEATING TO
   DESTABILIZE AIR MASS ALONG AN AXIS FROM SOUTHEAST MISSOURI INTO
   SOUTHEAST LOWER MICHIGAN.  WHILE SHORT WAVE TROUGH IS WEAKENING IN
   CONFLUENT UPPER FLOW REGIME ACROSS THE GREAT LAKES...FORCING FOR
   UPWARD VERTICAL MOTION APPEARS STRONG ENOUGH TO ENHANCE CONVECTIVE
   DEVELOPMENT AHEAD OF COLD FRONT ACROSS MICHIGAN LATE THIS AFTERNOON.
   EMBEDDED WITHIN FAVORABLY SHEARED 40+ KT MEAN FLOW ENVIRONMENT...A
   FEW SEVERE STORMS STILL APPEAR LIKELY. AN ISOLATED SUPERCELL IS
   ALSO POSSIBLE...BEFORE STRONGER FORCING SHIFTS INTO QUEBEC LATER
   THIS EVENING.
   
   DESPITE LACK OF UPPER SUPPORT...LOW-LEVEL CONVERGENCE MAY BE STRONG
   ENOUGH TO SUPPORT ADDITIONAL STRONG/SEVERE CONVECTION ALONG FRONT
   INTO PARTS OF NORTHERN/CENTRAL INDIANA...PERHAPS SOUTH CENTRAL
   ILLINOIS AND SOUTHEAST MISSOURI.  THREAT IS EXPECTED TO BE CONFINED
   TO LATE AFTERNOON/EARLY EVENING HOURS...BEFORE PRE-FRONTAL BOUNDARY
   LAYER BEGINS TO COOL WITH LOSS OF SURFACE HEATING.
   
   ..KERR.. 04/21/2004
   
   ...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 0100Z