SPC AC 211327
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0827 AM CDT WED APR 21 2004
   
   VALID 211300Z - 221200Z
   
   THERE IS A MDT RISK OF SVR TSTMS TO THE RIGHT OF A LINE FROM 35 ESE
   FYV 40 NNW HOT 45 NNE TXK 40 WNW TXK DUA 35 WSW ADM 20 ENE FSI 35
   SSW END 30 WSW BVO 45 NE TUL 35 ESE FYV.
   
   THERE IS A SLGT RISK OF SVR TSTMS TO THE RIGHT OF A LINE FROM 40 W
   CLE 50 W LOZ 10 N CBM 20 N MLU 20 N GGG 30 NNW DAL 20 S FSI 35 SE
   GAG 45 WSW P28 40 NNW P28 30 E EMP 50 NW SGF 20 S VIH 20 E BLV 35
   WNW IND 15 ESE APN.
   
   GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM 15 NNW HSE 35 NE DAN
   35 ENE TRI 25 WNW RMG 20 WNW TCL 20 NNE JAN 45 SSE LFK 20 SE NIR 45
   W NIR 35 NNE COT 10 WNW SEP 50 WSW SPS 20 W CDS 40 NNW TCC 30 WNW
   4BL 50 NE ELY 10 NE 4LW 40 ESE EUG 45 SSE AST 10 NE SEA 4OM 15 E CTB
   25 WNW OLF 55 SSE Y22 20 W HON 40 SSW OTG 45 SW FOD 25 E P35 20 E
   UIN 20 SSW RFD 35 N VOK 40 E MQT.
   
   ...THERE IS A MDT RISK OF SVR TSTMS ACROSS MUCH OF CENTRAL/ERN OK
   AND PORTIONS WRN AR FOR THIS AFTERNOON AND EVENING...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE SLIGHT RISK
   AREA AND EXTENDING EWD TO LOWER OH/TN VALLEYS TO ERN LOWER MI/WRN
   OH...
   
   ...SRN KS/MUCH OF OK/NRN TX EWD ACROSS SRN MO/AR TO LOWER TN
   VALLEY...
   ALTHOUGH NOT VERY WELL IDENTIFIED IN WV IMAGERY...MODELS AGREE /06Z
   ETA SLIGHTLY FASTER/ WITH SHOWING A SHORT WAVE TROUGH MOVING ACROSS
   THE FOUR CORNERS REGION AT 12Z.  THIS FEATURE WILL CONTINUE TO MOVE
   ESEWD WITHIN STRONG WNWLY FLOW ALOFT /50-55 KT AT 500 MB AND AROUND
   100 KT AT 250 MB/...REACHING CENTRAL OK BY 00Z.
   
   AT THE SURFACE...COLD FRONT EXTENDED FROM LOW OVER SWRN WI SWWD
   ACROSS CENTRAL MO TO NEAR OKC AND NWRN TX TO A SURFACE LOW.  THE DRY
   LINE THEN EXTENDED SWWD TO TX BIG BEND.  THE COLD FRONT IS EXPECTED
   TO BECOME STATIONARY TODAY ACROSS CENTRAL TO NERN OK INTO FAR SRN
   MO...WHILE THE NRN EXTENT MOVES EWD ACROSS THE GREAT LAKES/OH
   VALLEY.  MEANWHILE...THE DRY LINE WILL MIX EWD ACROSS SWRN OK AND
   WRN/CENTRAL TX...REACHING A LINE FROM JUST SW OKC SWD TO WEST OF FTW
   TO DRT BY 00Z. THE PRIMARY OUTFLOW BOUNDARY LEFT OVER FROM MONDAY
   NIGHT CONVECTION EXTENDED FROM LIT WWD JUST SOUTH OF I-40 INTO
   CENTRAL OK.
   
   SLY LOW-LEVEL WINDS IN THE WARM SECTOR WILL MAINTAIN MOISTURE
   ADVECTION NWD TODAY WITH SURFACE DEWPOINTS IN THE LOWER 60S ACROSS
   MUCH OF THE MODERATE RISK AREA.  THIS COMBINED WITH SURFACE HEATING
   AND STEEP LAPSE RATES ALREADY IN PLACE WILL RESULT IN MODERATE
   INSTABILITY /MLCAPE 1500-2000 J/KG/ THIS AFTERNOON ACROSS
   CENTRAL-ERN OK INTO WRN AR AND NRN TX. INCREASING LARGE SCALE
   ASCENT THIS AFTERNOON ASSOCIATED WITH SRN ROCKIES SHORT WAVE TROUGH
   AND LEFT EXIT REGION OF MID/UPPER LEVEL JET IS EXPECTED TO AID IN
   CONVECTIVE INITIATION ALONG THE TRIPLE POINT AND SURFACE BOUNDARIES
   BETWEEN 19-22Z.  MODERATE INSTABILITY...STEEP LAPSE RATES...AND DEEP
   LAYER SHEAR VALUES INCREASING TO AROUND 50 KT WILL SUPPORT
   SUPERCELLS.  GIVEN THAT DEEP LAYER SHEAR VECTORS WILL CROSS DRY LINE
   AND OTHER CONVECTIVE BOUNDARIES...DISCRETE SUPERCELLS WILL BE
   LIKELY.  MAGNITUDE OF DEEP LAYER SHEAR... MODERATE INSTABILITY...AND
   40 KT SSWLY LLJ NOSING INTO NERN TX/FAR SERN OK/SWRN AR WILL SUPPORT
   A POTENTIAL FOR A FEW STRONG TORNADOES ACROSS PORTIONS OF
   CENTRAL/ERN OK INTO WRN AR...AND SIGNIFICANT HAIL.  AS THE SHORT
   WAVE TROUGH MOVES EWD TOWARD AR THIS EVENING...STRONG TO SEVERE
   THUNDERSTORMS WILL MOVE INTO SRN MO/AR.
   
   ...ERN LOWER MI SSWWD TO LOWER OH/MID MS VALLEYS...
   EXTENSIVE CLOUDINESS EXTENDING FROM THE GREAT LAKES REGION SWWD
   ALONG THE MS RIVER VALLEY IS EXPECTED TO LIMIT SURFACE HEATING.
   A SHORT WAVE TROUGH WILL MOVE NEWD ACROSS THE GREAT LAKES REGION
   TODAY...WITH A SECOND WEAKENING SHORT WAVE TROUGH TRACKING NEWD
   ACROSS THE MID MS/LOWER OH VALLEYS.  COLD FRONT INITIALLY EXTENDING
   FROM SWRN WI INTO CENTRAL MO WILL MOVE EWD TODAY... REACHING CENTRAL
   LOWER MI TO SERN MO BY 21Z.
   
   VIS IMAGERY SHOWS SOME BREAKS IN THE CLOUDINESS AHEAD OF THE COLD
   FRONT WHICH MAY ALLOW FOR MARGINAL INSTABILITY AS THE COLD FRONT
   MOVES EWD.  ETA INDICATES A DRY SLOT WILL MOVE INTO SRN LOWER MI BY
   THIS AFTERNOON WHICH WOULD SUPPORT STRONGER INSTABILITY BY MID-LATE
   AFTERNOON FROM LOWER MI INTO NRN IND/NWRN OH.  STRONG DEEP LAYER
   SHEAR ORIENTED NEARLY PARALLEL TO THE SURFACE FRONT WILL SUPPORT THE
   DEVELOPMENT OF A SQUALL LINE FROM SERN LOWER MI INTO NERN-CENTRAL
   IND LATE THIS AFTERNOON.  MORE CLOUDINESS SWD TO THE MID MS VALLEY
   SHOULD LIMIT INSTABILITY WITH MORE OF A SCATTERED THREAT FOR STRONG
   TO SEVERE THUNDERSTORMS.  THIS ACTIVITY SHOULD WEAKEN DURING THE
   EVENING AS IT REACHES WRN OH/WRN KY WHERE THE BOUNDARY LAYER WILL BE
   STABILIZING.
   
   ...CENTRAL-ERN PA/NJ/DELMARVA REGION...
   A COUPLE OF WEAK SHORT WAVE TROUGH WILL MOVE ACROSS THE MID ATLANTIC
   REGION BY 18Z FOLLOWED BY SHORT WAVE RIDGING PRIOR TO AN UPSTREAM
   SHORT WAVE TROUGH OVER MS/AL MOVES INTO THIS AREA BY OR JUST AFTER
   00Z.  ETA MODEL IS OVER FORECASTING SURFACE DEWPOINTS IN THIS AREA
   TODAY WITH VALUES EXPECTED TO BE IN THE MID 50S TO AROUND 60.  WEAK
   SURFACE BOUNDARY EXTENDED FROM SOUTH CENTRAL PA SEWD ACROSS FAR ERN
   VA AT 12Z.  THIS BOUNDARY WILL MOVE NEWD TODAY.  LOW-LEVEL
   CONVERGENCE ALONG THIS BOUNDARY AND OROGRAPHIC ASCENT OVER THE
   HIGHER TERRAIN SHOULD SUPPORT ISOLATED THUNDERSTORMS THIS
   AFTERNOON...DESPITE WARM NOSE NEAR 700 MB.  STEEP LAPSE RATES AND
   LOW WET-BULB ZERO HEIGHTS WILL RESULT IN AN ISOLATED HAIL/DAMAGING
   WIND THREAT.  SOME INCREASE IN ACTIVITY MAY OCCUR AFTER 00Z WITH THE
   APPROACH OF THE MS/AL TROUGH...BUT BOUNDARY LAYER STABILIZATION AT
   THAT TIME WILL LIKELY INHIBIT ADDITIONAL THREAT FOR ORGANIZED
   STORMS.
   
   ..PETERS/CROSBIE.. 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 1630Z