SPC AC 210607
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0107 AM CDT WED APR 21 2004
   
   VALID 211200Z - 221200Z
   
   THERE IS A MDT RISK OF SVR TSTMS TO THE RIGHT OF A LINE FROM 30 NE
   DUA 45 NNE ADM 25 NNE OKC 25 WSW PNC 25 N PNC 35 NW BVO 35 NE BVO 20
   WSW UMN 20 SSE HRO 45 NW LIT 10 S HOT 35 NNE TXK 40 ENE PRX 30 NE
   DUA.
   
   THERE IS A SLGT RISK OF SVR TSTMS TO THE RIGHT OF A LINE FROM 50 NNE
   BUF 25 NNE PIT 30 SW CRW 45 ESE LOZ 40 WNW CHA 15 ENE GWO 30 SSE GLH
   40 SSW ELD 30 NNW GGG 30 NE DAL 25 ENE SPS CSM 15 NE GAG 30 SE DDC
   35 S RSL 20 ESE SLN 40 E EMP 50 NNE JLN 35 ENE SGF 50 ESE TBN 40 WNW
   MDH 25 W HUF 40 WSW FWA 25 E APN.
   
   GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM 15 NNW HSE 35 NE DAN
   35 ENE TRI 45 ENE HSV 20 ESE CBM 20 NNE JAN 45 SSE LFK 20 SE NIR 45
   W NIR 35 NNE COT 20 ESE BWD 40 SW SPS 10 NE 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 40 NNW BIS 35 NNW ABR 40 SSW OTG 45 SW FOD 20 E DSM 20
   WNW CID 20 ENE AUW 45 ENE MQT.
   
   ...THERE IS A MDT RISK OF SVR TSTMS ACROSS NCNTRL OK...ERN OK...WRN
   AR...FAR SW MO AND FAR SRN KS...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF KS...OK...NE
   TX...AR...SRN MO...FAR NRN LA...NRN MS...TN...SRN
   IL...IND...KY...OH...ERN LOWER MI...FAR WRN WV...FAR WRN TN AND FAR
   WRN NY...
   
   ...SRN PLAINS/CNTRL PLAINS/OZARKS...
   
   A WELL-DEFINED MOIST AXIS CURRENTLY EXISTS ACROSS ERN AND NRN OK
   WHERE LOWER TO MID 60S F SFC DEWPOINTS ARE IN PLACE. A WELL-DEFINED
   SHORTWAVE TROUGH IS LOCATED ACROSS THE TX PANHANDLE AND THIS SYSTEM
   WILL MOVE EWD TODAY LIKELY RESULTING IN A WIDESPREAD SEVERE WEATHER
   EVENT.
   
   WLY FLOW ALOFT WILL TAKE RESIDUAL CLOUD COVER FROM YESTERDAYS
   CONVECTION EWD INTO THE LOWER MS VALLEY THIS MORNING. THIS WILL
   LEAVE MOSTLY CLEAR SKIES ACROSS THE SRN AND CNTRL PLAINS FOR STRONG
   SFC HEATING THIS AFTERNOON. FOR THIS REASON...BELIEVE THE MODELS ARE
   UNDERESTIMATING THE AMOUNT OF INSTABILITY ACROSS OK AND NE TX THIS
   AFTERNOON. FORECAST SFC TEMPS IN THE MID 70S F SHOULD YIELD MODERATE
   INSTABILITY WITH 2000 TO 2500 J/KG ACROSS THE MODERATE RISK AREA. A
   STATIONARY FRONT IS CURRENTLY POSITIONED FROM SWRN OK EXTENDING NEWD
   ACROSS SRN MO AND THIS BOUNDARY WILL BE THE FOCUS FOR CONVECTIVE
   DEVELOPMENT THIS AFTERNOON.
   
   THE ETA/ETAKF AND GFS ARE ALL CONSISTENT DEVELOPING A STRONG
   VORTICITY MAX AND MOVING IT EWD ACROSS THE TX PANHANDLE INTO OK THIS
   AFTERNOON.. THIS WILL SPREAD STRONG LARGE-SCALE ASCENT ACROSS REGION
   WHICH SHOULD COINCIDE WELL WITH PEAK HEATING AND THE STRONGEST
   INSTABILITY. IN ADDITION...THE EXIT REGION OF A MID TO UPPER-LEVEL
   JET WILL BE IN PLACE ACROSS OK AND THIS WILL PROVIDE STRONG
   DIVERGENCE ALOFT. AS A RESULT...EXPECT CONVECTIVE INITIATION DURING
   THE AFTERNOON TO BEGIN ACROSS CNTRL OK AND SPREAD EWD ACROSS THE
   MODERATE RISK AREA DURING THE LATE AFTERNOON AND EVENING HOURS. THE
   MID-LEVEL FLOW WILL INCREASE DURING THE DAY AND THIS WILL PROVIDE
   STRONG DEEP LAYER SHEAR OF 50 TO 60 KT FAVORABLE FOR SUPERCELL
   CLUSTERS. A PLUME OF STEEP LAPSE RATES ASSOCIATED WITH THE EXIT
   REGION OF THE MID-LEVEL JET WILL MAKE LARGE HAIL A THREAT WITH THE
   STORMS.
   
   FORECAST SOUNDINGS FOR ERN OK SHOW STRONG LOW-LEVEL VEERING WITH 0-3
   STORM RELATIVE HELICITY ABOVE 400 M2/S2 THIS AFTERNOON. AS THE
   LOW-LEVEL JET INCREASES BETWEEN 22Z-02Z...CONDITIONS WILL BE
   FAVORABLE FOR TORNADOES WITH A FEW SIGNIFICANT TORNADOES POSSIBLE.
   THE MOST FAVORABLE AREA FOR STRONG TORNADOES SHOULD BE ACROSS THE
   ERN HALF OF OK AND IN WRN AR ALONG THE NW EDGE OF THE LOW-LEVEL JET
   AXIS.
   
   THE COMBINATIONS OF STEEP LAPSE RATES...STRONG DEEP LAYER SHEAR AND
   STRENGTHENING LOW-LEVEL FLOW WILL CONTINUE TO PRODUCE A LARGE HAIL
   AND WIND DAMAGE THREAT AS THE SUPERCELL CLUSTERS TRACK EWD ACROSS AR
   OVERNIGHT.
   
   
   ...OH AND TN VALLEYS/UPPER OH VALLEY...
   
   A COLD FRONT WILL MOVE SEWD ACROSS IL/IND AND OH TODAY. CONVECTION
   WILL LIKELY BE ONGOING ALONG THE FRONT THIS MORNING AND WILL
   GRADUALLY MOVE INTO THE WARM SECTOR DURING THE DAY. AS THE LINE
   INTERACTS WITH THE LOW-LEVEL JET ACROSS OH...KY AND TN DURING THE
   AFTERNOON...ISOLATED WIND DAMAGE WILL BE POSSIBLE ESPECIALLY NEAR
   PEAK HEATING WITH BOWING SEGMENTS.
   
   PARTIAL CLEARING SHOULD OCCUR BEHIND THE LINE NEAR THE FRONTAL
   BOUNDARY AND THIS WILL FOCUS AN AXIS OF INSTABILITY FROM IND SWD
   ALONG THE MID MS RIVER VALLEY. AS SFC HEATING OCCURS...STRONG
   INSTABILITY SHOULD DEVELOP ALONG THE WRN EDGE OF THE SLIGHT RISK
   AREA. IN ADDITION...MID-LEVEL LAPSE RATES WILL BE BETTER IN THIS
   CORRIDOR AND A THREAT FOR LARGE HAIL SHOULD EXIST WITH THE STRONGER
   UPDRAFTS.
   
   
   ...MID-ATLANTIC STATES...
   
   SFC ANALYSIS CURRENTLY SHOWS A MOIST AXIS IN PLACE ACROSS ERN VA AND
   MD WITH SFC DEWPOINTS IN THE UPPER 50S AND LOWER 60S F. LOW-LEVEL
   FLOW WILL INCREASE TODAY AS AN UPPER-TROUGH APPROACHING THE GREAT
   LAKES...SHIFTING THE LOW-LEVEL JET NEWD ACROSS THE NEW ENGLAND
   STATES. THIS WILL LIKELY ADVECT THE LOW-LEVEL MOISTURE INTO ACROSS
   MD AND SRN PA THIS AFTERNOON. A WARM FRONTAL BOUNDARY EXISTS EAST OF
   THE MOIST AXIS AND THIS WILL BE A FOCUS FOR STORM INITIATION. STORMS
   SHOULD DEVELOP ALONG THE BOUNDARY AND SPREAD NEWD INTO THE NEW
   ENGLAND STATES.
   
   FORECAST SOUNDINGS SHOW 30 TO 35 KT OF DEEP LAYER SHEAR AND THIS
   SHOULD SUPPORT MULTICELL STORMS. THIS COMBINED WITH COLD MID-LEVEL
   TEMPS MAY BE ENOUGH FOR MARGINAL HAIL OR STRONG WIND WITH THE
   CONVECTION.
   
   ..BROYLES/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 1300Z