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May- 8-2003 1300 UTC Day 1 Convective Outlook
Public Severe Weather Outlook

The SPC is forecasting an outbreak of severe thunderstorms today and tonight across portions of the United States. This is an extremely dangerous situation. Please read the latest public statement about this event.

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1300 UTC Day 1 Outlook Graphic

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1300 UTC Tornado probabilities graphic   1300 UTC Damaging wind probabilities graphic   1300 UTC Large hail probabilities graphic
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   STORM PREDICTION CENTER...NWS/NCEP...NORMAN OK 
   DAY 1 CONVECTIVE OUTLOOK...REF AWIPS GRAPHIC PGWE46 KWNS.
   
   VALID 081300Z - 091200Z
   
   THERE IS A HIGH RISK OF SVR TSTMS ACROSS NERN KS...NWRN MO AND
   EXTREME SERN NEB THIS AFTERNOON AND EVENING.  THE HIGH RISK AREA IS
   TO THE RIGHT OF A LINE FROM 35 SE OJC 10 NNE EMP 30 WNW MHK 25 WSW
   BIE 50 NE FNB 10 WNW P35 20 NNW SZL 35 SE OJC.
   
   SURROUNDING THE HIGH RISK AREA...THERE IS A MDT RISK OF SVR TSTMS
   ACROSS FAR NERN OK...ERN KS...SERN NEB...SWRN IA...AND MUCH OF WRN
   MO THIS AFTERNOON INTO THE OVERNIGHT HOURS.  THE MDT RISK AREA IS
   TO THE RIGHT OF A LINE FROM 35 NE ICT 10 SSE SLN 40 WSW CNK 55 WNW
   CNK 20 S HSI 30 E OMA 35 ENE LWD 45 SE IRK 30 WNW TBN 25 SW JLN 10
   NNW TUL 20 SSE PNC 35 NE ICT.
   
   THERE IS A SLGT RISK OF SVR TSTMS TO THE RIGHT OF A LINE FROM
   20 SSW DAY 25 NNW HSS 25 NW MCN 45 ESE GWO 45 NE TXK 50 WSW TYR
   45 W AUS 20 SSE JCT 40 E SJT 10 ESE FSI END 30 NNE P28 25 SW RSL
   HLC 30 N GLD 10 NW IML 15 WNW LBF 25 NNW FRM 20 NE LSE 15 SSW MKE
   20 SSW DAY.
   
   GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM 20 SSE SSI 30 W ABY
   25 SW SEM 55 WSW MLU 45 SW TYR 15 ESE SAT 10 NW LRD ...CONT...
   30 SE P07 70 SW SJT 45 SSW ABI 25 WNW FSI 50 E GAG 20 ESE DDC
   40 NNW GCK 25 ENE PUB 35 SSE DRO 80 S 4BL 30 SE DRA 60 N NID
   55 NE MER 50 W SAC 15 NE 4BK 30 ENE OTH 25 W RDM 55 NW BNO
   30 SSE BKE 25 S MSO 25 SSW LVM 30 W SHR 20 SW 4BQ 25 WSW DIK
   55 N MOT ...CONT... 20 WNW RRT 35 NNE FAR 30 NNW AXN 45 WSW RHI
   20 NE TOL ...CONT... 10 NNE ROC UCA 40 SSW BTV 15 SSE MPV
   20 NNW ORH 10 ESE ISP.
   
   ...SYNOPSIS...
   MID-LEVEL PATTERN IS FORECAST TO AMPLIFY THIS PERIOD AS MID-LEVEL
   SPEED MAX DIVES SWD ALONG THE W COAST AND INTO CA DURING THE FIRST
   HALF OF THE PERIOD...RESULTING IN AMPLIFICATION OF THE WRN U.S.
   TROUGH.  AS SECONDARY VORT MAX NOW OVER THE SRN GREAT BASIN / AZ
   EJECTS NEWD INTO THE CENTRAL PLAINS...SHORT-WAVE RIDGING WILL
   STRENGTHEN IN RESPONSE INVOF THE MS VALLEY THROUGH THE FIRST HALF
   OF THE PERIOD.  DURING THE SECOND HALF OF THE PERIOD...THIS RIDGE
   SHOULD RETREAT EWD ACROSS THE MS VALLEY AS AFOREMENTIONED VORT MAX
   MOVES NEWD TOWARD THE NRN PLAINS.
   
   AT THE SURFACE...CYCLOGENESIS IS EXPECTED IN LEE OF THE ROCKIES
   EARLY IN THE PERIOD ALONG WRN EDGE OF RETREATING WARM FRONT.  THIS
   LOW IS EXPECTED TO MOVE ENEWD INTO N CENTRAL KS BY 09/00Z...AND
   THEN NNEWD INTO SRN MN BY THE END OF THE PERIOD AHEAD OF UPPER
   FEATURE.  
   
   ...CENTRAL PLAINS EWD INTO THE MID MS / LOWER OH VALLEY...
   LOCALIZED SEVERE WEATHER OUTBREAK IS FORECAST TODAY ACROSS THE
   LOWER MO VALLEY REGION TODAY...WITH A FEW STRONG TORNADOES
   ANTICIPATED IN ADDITION TO VERY LARGE HAIL AND STRONG / DAMAGING
   WINDS.
   
   ELEVATED THUNDERSTORMS ARE MOVING NEWD ACROSS THE ANTICIPATED
   OUTBREAK AREA THIS MORNING IN REGION OF STRONG WARM ADVECTION NORTH
   OF RETREATING WARM FRONT.  AS UPPER FEATURE APPROACHES FROM THE
   SWRN U.S. AND SURFACE LOW DEEPENS...VERY MOIST LOW-LEVEL AIRMASS IS
   EXPECTED TO MOVE NWD INTO ERN KS / WRN MO BY MID AFTERNOON. 
   ALTHOUGH SUBSIDENCE / CAPPING INVERSION ASSOCIATED WITH SHORT-WAVE
   RIDGING SHOULD SUPPRESS CONVECTIVE DEVELOPMENT THROUGH EARLY
   AFTERNOON...IT APPEARS THAT CONVECTIVE DEVELOPMENT WILL OCCUR INVOF
   LOW / WARM FRONT / DRYLINE ACROSS N CENTRAL AND ERN KS.  
   
   ABOVE THE MOISTENING / WARMING BOUNDARY LAYER...FAIRLY STEEP
   /AROUND 7 C/KM/ LAPSE RATES WILL SPREAD ACROSS THE REGION ON SWLY
   FLOW ALOFT...LIKELY RESULTING IN 2000 TO 3000 J/KG MEAN-LAYER CAPE.
   
   WITH INCREASING / SELY LOW-LEVEL FLOW E AND NE OF SURFACE LOW /
   INVOF WARM FRONT BENEATH 70 TO 80 KT SWLY MID-LEVEL JET STREAK
   SPREADING NEWD ACROSS THE AREA...DEEP-LAYER WIND PROFILES WILL
   FAVOR RAPID DEVELOPMENT OF ROTATION WITHIN INITIATING UPDRAFTS. 
   FURTHERMORE...SFC-1 KM SHEAR / HELICITY FORECAST ON THE ORDER OF 30
   TO 40 KTS AND 300 TO 500 RESPECTIVELY IS STRONGLY SUPPORTIVE OF
   LOW-LEVEL ROTATION.  GIVEN MOIST BOUNDARY LAYER / LOW
   LCLS...TORNADOES ARE EXPECTED -- WITH A FEW STRONG / LONG-LIVED
   TORNADOES POSSIBLE.  VERY LARGE HAIL CAN ALSO BE EXPECTED ALONG
   WITH LOCALLY DAMAGING WINDS.  GREATEST THREAT APPEARS TO EXIST
   ACROSS EXTREME SERN NEB / THE NERN 2/3 OF KS INITIALLY...AND THEN
   SHOULD SPREAD EWD ACROSS THE NRN 2/3 OF MO DURING THE EVENING.  
   
   OVERNIGHT...STORMS SHOULD INCREASE IN COVERAGE AND SPREAD EWD
   ACROSS MO SRN IA INTO IL...WITH A CONTINUED SEVERE THREAT THROUGH
   MUCH OF THE PERIOD.
   
   
   ...OK / TX REGION AHEAD OF DRYLINE...
   SCATTERED TO ISOLATED THUNDERSTORMS ARE FORECAST TO DEVELOP ALONG
   / AHEAD OF DRYLINE BY 20 TO 21Z AS SWRN UPPER FEATURE MOVES JUST N
   OF THE REGION.  VERY MOIST LOW-LEVEL AIRMASS BENEATH STEEP MID-
   LEVEL LAPSE RATES SHOULD YIELD 1500 TO 3000 J/KG MEAN-LAYER
   CAPE...WHICH COMBINED WITH 50 TO 70 KTS OF FLOW AT MID-LEVELS ALONG
   SRN FRINGE OF JET STREAK WILL RESULT IN FAVORABLE DEEP-LAYER SHEAR
   FOR SUPERCELLS.  ALTHOUGH LOW-LEVEL WINDS WILL BE MORE SLY AND
   LIKELY SOMEWHAT WEAKER...SHEAR WILL BE SOMEWHAT LESS FAVORABLE FOR
   TORNADOES WITH SWD EXTENT INTO TX THAN FURTHER N ACROSS KS / MO. 
   HOWEVER...A COUPLE OF TORNADOES WILL BE POSSIBLE INTO CENTRAL TX...
   ALONG WITH LARGE HAIL AND LOCALLY DAMAGING WINDS.  OVERALL THREAT
   WILL LIKELY DECREASE OVERNIGHT AS STRONGER UPPER SUPPORT FOR
   CONVECTION SHIFTS NEWD AWAY FROM THE AREA...BUT A FEW SEVERE STORMS
   WILL LIKELY PERSIST WELL INTO THE EVENING / OVERNIGHT.
   
   ...SOUTHEAST / TN AND OH VALLEYS...
   AS WARM FRONT RETREATS NWD FROM NRN PORTIONS OF THE GULF COAST
   STATES INTO TN VALLEY REGION AND TOWARD THE OH VALLEY REGIONS...
   NWD ADVECTION OF VERY MOIST LOW-LEVEL AIRMASS WILL OCCUR.  BY
   MIDDAY / EARLY AFTERNOON....EXPECT THUNDERSTORMS TO DEVELOP BY
   MIDDAY AND THEN INCREASE THROUGH THE AFTERNOON.  WITH MODERATELY
   STRONG /40 TO 50 KT/ WLY MID-LEVEL JET ACROSS THIS REGION...
   POTENTIAL EXISTS FOR ISOLATED SUPERCELLS WITH LARGE HAIL / DAMAGING
   WINDS AND PERHAPS A TORNADO OR TWO.  SEVERE THREAT SHOULD DECREASE
   THROUGH THE EVENING WITH SHORT-WAVE RIDGING FORECAST TO INCREASE
   ALOFT AND LOSS OF DAYTIME HEATING.  
   
   ..GOSS.. 05/08/03
   
   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED FOR 1630Z
        
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