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May-12-2004 1300 UTC Day 1 Convective Outlook
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   SPC AC 121301
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0801 AM CDT WED MAY 12 2004
   
   VALID 121300Z - 131200Z
   
   THERE IS A SLGT RISK OF SVR TSTMS TO THE RIGHT OF A LINE FROM 70 NW
   ANJ 30 WNW MKE 20 W UMN 15 SW TUL 30 NNE OKC 15 NE FSI 20 WNW LTS 20
   WSW GAG 10 WNW LBL 15 SSW LAA 30 E COS 35 ENE DEN 40 NW AKO 30 SSW
   IML 20 S HSI 35 ENE OMA 25 NW MCW 20 NNE ELO.
   
   GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM 25 WNW DRT 25 N SJT
   40 S CDS 55 NNW CDS 40 SSE EHA 50 SSE LHX 40 NW TAD 10 N DRO 15 SSW
   CNY 20 W ENV 40 S OWY 60 W OWY 20 SSE BNO 10 NNE PDT 35 W PUW 40 SSW
   3DU 20 SSW LVM 20 ENE CPR BFF 10 NE LBF 15 NE BUB YKN 15 N BKX 30 E
   FAR RRT ...CONT... 25 E MSS 20 NE LEB PSM ...CONT... 40 SSE JAX 45
   SE CTY ...CONT... 35 NE CRP 20 S LRD.
   
   ...THERE IS A SLGT RISK OF SVR TSTMS FROM THE UPPER MS VALLEY /
   GREAT LAKES SWWD INTO KS / ERN CO / OK...
   
   ...SYNOPSIS...
   MAIN UPPER TROUGH NOW OVER THE ROCKIES WILL MOVE VERY SLOWLY EWD
   THROUGH THIS PERIOD...WHILE SEVERAL WEAKER FEATURES MOVE NEWD ACROSS
   THE PLAINS IN BELT OF STRONGER SWLY MID-LEVEL FLOW ALONG ERN
   PERIPHERY OF MAIN TROUGH.  A SECOND SHORT-WAVE TROUGH -- WELL AHEAD
   OF MAIN TROUGH -- NOW EXTENDING FROM ERN KS SWD TO THE TX / LA
   BORDER WILL CONTINUE MOVING SLOWLY EWD ACROSS THE MID AND LOWER MS
   VALLEY THROUGH THE PERIOD.
   
   AT THE SURFACE...COLD FRONT ASSOCIATED WITH MAIN UPPER TROUGH NOW
   EXTENDS FROM LOW PRESSURE OVER MN SWWD INTO OK / NRN TX PANHANDLES
   AND THEN WWD INTO SRN CO.  THIS FRONT IS FORECAST TO MOVE STEADILY
   EWD ACROSS THE GREAT LAKES...WHILE SEWD SURGE INTO THE SRN PLAINS
   SLOWS THROUGH THE MORNING.  BY AFTERNOON...SURFACE LOW IS FORECAST
   TO DEEPEN ALONG BOUNDARY ACROSS SERN CO.  THIS WILL LIKELY ALLOW
   BOUNDARY TO RETREAT NWD INTO WRN KS / ERN CO THIS AFTERNOON.  BY
   LATE IN THE PERIOD...BOUNDARY SHOULD CONTINUE ITS SWD PUSH ACROSS
   THE TX / OK PANHANDLE REGION.
   
   ...UPPER MS VALLEY / WRN GREAT LAKES SWWD INTO KS / OK / ERN CO...
   MID TO UPPER 60S DEWPOINTS EXIST AHEAD OF ADVANCING COLD FRONT
   ATTM...WHILE CAPPED LOW-LEVEL AIRMASS IS RESULTING IN WIDESPREAD LOW
   CLOUDINESS OVER THE CENTRAL AND SRN PLAINS.  HOWEVER...DAYTIME
   HEATING / MIXING SHOULD EVENTUALLY ALLOW CLOUDS TO BREAK UP AND
   HEATING TO COMMENCE...WITH 2000 TO 3000 J/KG MEAN-LAYER CAPE
   EXPECTED BY AFTERNOON. 
   
   STORMS ARE FORECAST TO INITIATE INVOF COLD FRONT -- INITIALLY ACROSS
   WRN KS OR WWD INTO CO IN SELY UPSLOPE FLOW REGIME.  ISOLATED STORMS
   ARE ALSO FORECAST TO DEVELOP SWD ALONG DRYLINE ACROSS OK / TX.
   
   STRONGEST INSTABILITY / SHEAR COMBINATION IS FORECAST ACROSS
   KS...WHERE 40 TO 50 KT 0-6 KM SHEAR IS EXPECTED.  STORMS SHOULD
   THEREFORE BECOME RAPIDLY SUPERCELLULAR...WITH VERY LARGE HAIL AND
   DAMAGING WINDS EXPECTED.  AN ISOLATED TORNADO WILL ALSO BE
   POSSIBLE...PARTICULARLY FROM ERN CO INTO WRN KS WHERE LOW-LEVEL
   SHEAR WILL BE MOST FAVORABLE.
   
   FURTHER SWD ALONG DRYLINE...SHEAR IS FORECAST TO BE WEAKER -- BUT
   STILL STRONG ENOUGH FOR MULTICELLS / WEAK UPDRAFT ROTATION.  THIS
   COMBINED WITH STRONG INSTABILITY SUPPORTS A THREAT FOR LARGE HAIL
   AND LOCALLY DAMAGING WINDS.
   
   OVERNIGHT...STORMS WILL LIKELY INCREASE IN COVERAGE AS LOW-LEVEL JET
   DEVELOPS.  SEVERE THREAT SHOULD PERSIST THROUGH MUCH OF THE NIGHT AS
   ONE OR MORE MCSS LIKELY EVOLVE OVER KS / OK. 
   
   ...UPPER MS VALLEY INTO THE WRN GREAT LAKES REGION...
   SHOWERS AND STORMS ARE ONGOING ATTM ALONG COLD FRONT FROM MN SSWWD
   INTO NERN KS.  LOW 60S DEWPOINTS COMBINED WITH DAYTIME HEATING
   SHOULD ALLOW MARGINAL AIRMASS DESTABILIZATION TO OCCUR.  AS A
   RESULT...EXPECT SOME INCREASE IN STORM INTENSITY BY AFTERNOON ALONG
   / AHEAD OF FRONT.  IN ADDITION TO LIMITED INSTABILITY...STRONGER
   DEEP-LAYER WIND FIELD IS FORECAST TO REMAIN ON THE COLD SIDE OF
   SURFACE BOUNDARY.  HOWEVER...INSTABILITY / SHEAR IN THE IMMEDIATE
   VICINITY OF COLD FRONT WILL LIKELY SUPPORT LOCALLY DAMAGING WINDS
   AND SOME HAIL WITH A FEW OF THE STRONGER STORMS.  ALTHOUGH
   CONVECTION SHOULD SPREAD EWD INTO THE GREAT LAKES REGION
   OVERNIGHT...SEVERE THREAT SHOULD SLOWLY DECREASE WITH THE LOSS OF
   DAYTIME HEATING.
   
   ...MID AND LOWER MS VALLEY REGION...
   MOIST LOW-LEVEL AIRMASS IS EVIDENT THIS MORNING ACROSS THE MIDDLE
   AND LOWER MS VALLEY REGION AHEAD OF WEAK UPPER SHORT-WAVE TROUGH. 
   STORM CLUSTER CONTINUES ACROSS AR / LA / WRN MS WITHIN MESOSCALE
   CIRCULATION NOW OVER FAR SERN AR ATTM. AS THIS FEATURE AND SECOND /
   WEAKER CIRCULATION EVIDENT OVER W CENTRAL MO ATTM MOVE EWD THROUGH
   THIS AFTERNOON...AND INCREASE IN STORMS IS EXPECTED ALTHOUGH
   INTENSITY IS FORECAST TO BE SOMEWHAT LIMITED DUE TO ONLY MARGINAL
   INSTABILITY.  NONETHELESS...COMBINATION OF MODERATE / 20 TO 30 KT /
   WINDS THROUGH A DEEP LAYER AND PRESENCE OF MESOSCALE CIRCULATION
   CENTERS MAY ALLOW SOME STORM ORGANIZATION / PERSISTENCE.  ALONG WITH
   A THREAT FOR A LOCALLY DAMAGING GUST OR TWO...AN ISOLATED TORNADO
   WILL ALSO BE POSSIBLE GIVEN FAIR DEGREE OF LOW-LEVEL SHEAR AND MOIST
   LOW-LEVEL AIRMASS.  DIURNAL WEAKENING OF CONVECTION THIS EVENING
   SHOULD ALLOW ANY SEVERE THREAT TO DIMINISH.
   
   ..GOSS / TAYLOR.. 05/12/2004
   
   ...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
        
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