SPC AC 201958
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0258 PM CDT TUE APR 20 2004
   
   VALID 202000Z - 211200Z
   
   THERE IS A SLGT RISK OF SVR TSTMS TO THE RIGHT OF A LINE FROM SPI
   SLO CGI JBR HOT PRX 35 SE SPS OKC END 40 ESE P28 ICT TOP FNB OMA OFK
   YKN OTG FRM ALO BRL SPI.
   
   GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM 25 N UIL 35 SSW CLM
   35 ESE AST 15 SW EUG 4BK.
   
   GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM 10 W BUF CXY 15 S ACY
   ...CONT... 15 ENE ECG 40 N RWI GSO 10 SE TRI 10 S LEX SDF MKL SHV 25
   S CLL 25 E SAT 45 N HDO JCT 10 NE SJT 10 N SPS CSM GAG GLD DEN ASE
   PUC SLC TWF BOI 10 SSE LWS 10 ENE GEG 20 E FCA 10 WSW HVR SDY 40 W
   P24 30 ENE MOT 65 NNW DVL ...CONT... 35 ESE RRT FAR ATY STC RHI 50
   NNW ANJ.
   
   ...THERE IS A SLGT RISK OF SVR TSTMS LATE THIS AFTN/TONIGHT FROM
   PARTS OF THE CNTRL PLAINS INTO THE MIDDLE MISSISSIPPI VALLEY....
   
   ...PLAINS/MISSISSIPPI VALLEY...
   LARGE-SCALE TROUGH...WITH A COUPLE OF EMBEDDED SHORT WAVES
   ...CONTINUES TO SHIFT EASTWARD INTO THE PLAINS/MISSISSIPPI
   VALLEY...AS EXIT REGION OF INTENSE HIGH-LEVEL JET PROGRESSES ACROSS
   THE GREAT BASIN INTO THE CENTRAL ROCKIES.  SURFACE CYCLOGENESIS IS
   ONGOING ACROSS THE MID MISSOURI VALLEY IN ASSOCIATION WITH INITIAL
   SHORT WAVE...WHICH WILL CONTINUE TO LIFT NORTHEASTWARD TOWARD THE
   UPPER GREAT LAKES REGION THROUGH THE REMAINDER OF THE FORECAST
   PERIOD.
   
   SURFACE TROUGH/DRY LINE WHICH EXTENDS SOUTH OF SURFACE LOW IS
   CURRENTLY BECOMING FOCUS FOR MAXIMUM DESTABILIZATION/INCREASING
   CONVECTIVE DEVELOPMENT.  THIS IS EXPECTED TO REMAIN THE CASE THROUGH
   THE REST OF THE AFTERNOON AND EVENING HOURS.  BY 21/00Z...DRY LINE
   APPEARS LIKELY TO EXTEND ROUGHLY ALONG/EAST OF THE INTERSTATE-35
   CORRIDOR FROM NORTHEAST KANSAS INTO CENTRAL OKLAHOMA.  STRONG
   HEATING ALONG WESTERN EDGE OF LOWER 60S DEW POINTS WILL CONTRIBUTE
   TO MEAN MIXED LAYER CAPE IN EXCESS OF 1000 J/KG...PERHAPS 1500
   J/KG...SUPPORTING VIGOROUS UPDRAFTS IN MODERATELY SHEARED
   ENVIRONMENT FAVORABLE FOR SUPERCELLS.  ISOLATED TORNADOES ARE
   POSSIBLE...MAINLY NEAR MID-LEVEL SPEED MAXIMUM MIGRATING OUT OF
   SOUTHEAST KANSAS/NORTHEAST OKLAHOMA INTO THE MISSOURI OZARKS.
   HOWEVER...PRIMARY THREAT APPEARS TO BE LARGE HAIL/ISOLATED DAMAGING
   WIND GUSTS.
   
   AS NOSE OF UPPER JET PROGRESSES INTO THE SOUTH CENTRAL PLAINS THIS
   EVENING...UPPER FLOW REGIME WILL BECOME INCREASINGLY
   DIFLUENT/DIVERGENT ALONG/AHEAD OF MID-LEVEL WIND SHIFT ROTATING
   ACROSS THE OZARKS.  AIDED BY MOISTURE TRANSPORT ON SOUTHERLY
   LOW-LEVEL JET AHEAD OF WIND SHIFT...SQUALL LINE MAY EVENTUALLY
   EVOLVE WITH INCREASING POTENTIAL FOR DAMAGING WIND GUSTS.  ACTIVITY
   WILL PROGRESS ACROSS EASTERN MISSOURI/NORTHERN ARKANSAS BEFORE
   SLOWLY WEAKENING OVERNIGHT AS IT PROGRESSES EAST OF LOW-LEVEL MOIST
   AXIS.
   
   ...MIDDLE MISSOURI VALLEY...
   ALTHOUGH CUT OFF FROM BETTER LOW-LEVEL MOISTURE/INSTABILITY...AN
   ISOLATED SUPERCELL IS POSSIBLE ALONG WARM FRONTAL ZONE NEAR/JUST
   EAST OF DEEPENING SURFACE LOW ACROSS WESTERN IOWA THROUGH EARLY
   EVENING.
   
   ...UPPER OHIO VALLEY/MID ATLANTIC COAST STATES...
   WEAKENING MID/UPPER SPEED MAXIMUM ACCELERATING ACROSS THE TENNESSEE
   VALLEY IS PROVIDING SUPPORT FOR ONGOING LINE OF CONVECTION NOW
   SPREADING INTO THE UPPER OHIO VALLEY/CENTRAL APPALACHIANS.  AIR MASS
   HAS DESTABILIZED ALONG/SOUTH OF FRONTAL ZONE EXTENDING FROM THE
   NORTHERN MID ATLANTIC COAST INTO THE UPPER OHIO VALLEY...AND
   THUNDERSTORMS MAY INTENSIFY FURTHER LATE THIS AFTERNOON INTO EARLY
   EVENING.  BETTER BOUNDARY LAYER MOISTURE EXISTS ACROSS WEST
   VIRGINIA...WHERE CAPE MAY BECOME SUFFICIENT FOR A BRIEF HAIL THREAT
   THIS AFTERNOON.  OTHERWISE...IN DRIER...BUT DEEP MIXED BOUNDARY
   LAYER EAST OF THE APPALACHIANS...A FEW STRONG GUSTS
   APPROACHING/BRIEFLY EXCEEDING SEVERE LIMITS ARE POSSIBLE ACROSS
   WESTERN//CENTRAL/NORTHERN VIRGINIA.
   
   ..KERR.. 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 0100Z