[LeArc] DAY 1 CONVECTIVE OUTLOOK

[Duane Whittingham]

    DAY 1 CONVECTIVE OUTLOOK
    NWS STORM PREDICTION CENTER NORMAN OK
    1211 AM CDT WED MAY 12 2004

    VALID 121200Z - 131200Z

    THERE IS A SLGT RISK OF SVR TSTMS TO THE RIGHT OF A LINE FROM 70 WNW
    ANJ 15 ESE JVL 45 NE COU 15 NNW SGF 50 NW FYV 30 NE OKC 25 NE FSI 35
    NW LTS 35 E LBL 35 SW GCK 20 SSW LAA 40 E COS 30 SE CYS 20 WSW SNY
    35 S MCK 10 ENE CNK OMA 30 WNW RWF 20 NNW INL.

    GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM 50 SE DRT 35 N HDO 10
    SE BWD 30 N ABI 40 S CDS 65 ENE AMA 20 S LBL 50 SSE LHX 20 W 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 60
    ENE ANW 10 WSW HON JMS 70 N GFK ...CONT... 25 E MSS 30 SE SLK 25 NNE
    PSF ISP ...CONT... WAL 30 W RIC 20 SSE LYH 15 WNW GSO 40 SE CLT 15
    SSE CHS ...CONT... 40 SSE JAX 45 SE CTY.

    ...THERE IS A SLGT RISK OF SVR TSTMS FROM THE WRN GREAT LAKES SWWD
    INTO PORTIONS OF THE CNTRL AND SRN PLAINS...

    ...SYNOPSIS...
    DEEP...MID-LEVEL TROUGH WILL REMAIN IN PLACE ACROSS THE
    INTERMOUNTAIN W/HIGH PLAINS REGION THROUGH THE DAY 1 PERIOD WITH
    SEVERAL SMALLER-SCALE VORTICITY MAXIMA TRANSLATING THROUGH THE MEAN
    TROUGH POSITION. THE FIRST OF WHICH /CURRENTLY OVER S-CNTRL WY/WRN
    NEB/ WILL EJECT NEWD ACROSS ERN ND/NWRN MN LATER TODAY AND INTO
    MANITOBA/WRN ONTARIO OVERNIGHT. THE NEXT SIGNIFICANT UPSTREAM
    VORTICITY MAX IS CURRENTLY OVER CNTRL NV/WRN UT. THIS FEATURE WILL
    ROUND THE TROUGH BASE AND LIFT NEWD INTO THE CNTRL HIGH PLAINS LATE
    THIS AFTERNOON OR EARLY EVENING...PRIOR TO PROGRESSING NEWD INTO ERN
    NEB/IA BY THURSDAY MORNING.

    AT THE SURFACE...CYCLONE ATTENDANT TO LEAD VORTICITY MAX WILL
    DEVELOP NEWD FROM W-CNTRL INTO N-CNTRL MN TODAY WITH TRAILING COLD
    FRONT SURGING SEWD. BY EARLY EVENING...FRONTAL POSITION SHOULD
    ROUGHLY EXTEND FROM WRN WI SWWD THROUGH CNTRL PORTIONS OF IA AND KS
    TO DEEPENING SECONDARY LOW OVER FAR SWRN KS/OK PNHDL REGION. PORTION
    OF COLD FRONT IN CLOSER PROXIMITY TO THIS SECONDARY LOW PRESSURE
    SHOULD TEND TO REMAIN MORE QUASI-STATIONARY OWING TO PRESSURE
    FALLS/WAA ON COLD SIDE OF BOUNDARY. FINALLY...DRYLINE SHOULD SHARPEN
    THROUGH THE DAY AS IT MIXES EWD...LIKELY EXTENDING FROM SECONDARY
    LOW SWD THROUGH ERN TX PNHDL OR WRN OK INTO W-CNTRL TX.

    ...WRN GREAT LAKES...
    PRE-FRONTAL TSTM CLUSTERS/LINE SEGMENTS WILL LIKELY BE ONGOING
    INITIALLY FROM N-CNTRL MN/MN ARROWHEAD SWD INTO CNTRL MN AND NERN
    NEB. ALTHOUGH CONVECTIVELY-PROCESSED MID-LEVEL LAPSE RATES ARE
    EXPECTED TO BE ONLY MOIST ADIABATIC AT BEST...MOIST FEED OF LOWER TO
    MID 60S DEWPOINTS AHEAD OF SURFACE CYCLONE AND ATTENDANT COLD FRONT
    SHOULD AID IN DESTABILIZATION PROCESS. THIS MOISTURE COUPLED WITH
    DIABATIC HEATING WILL ALLOW POCKETS OF MODERATE INSTABILITY TO
    DEVELOP ACROSS WI SWD INTO WRN IL AND CNTRL/ERN IA WITH MLCAPES
    APPROACHING 500-1500 J/KG.

    REDEVELOPMENT AND/OR RE-INTENSIFICATION OF ONGOING TSTMS IS
    ANTICIPATED BY AFTERNOON WITHIN DESTABILIZING AIRMASS OVER ERN MN
    INTO WRN WI AND CNTRL/ERN IA. STORMS SHOULD TEND TO BECOME ALIGNED
    IN FRONTAL-PARALLEL BANDS OR CLUSTERS AND SPREAD EWD ACROSS WI INTO
    THE WRN UP OF MI TONIGHT. ALTHOUGH THE STRONGEST MID AND UPPER-LEVEL
    WIND FIELDS WILL REMAIN TO THE W IN THE POST-FRONTAL COLD
    AIR...MARGINALLY STRONG DEEP-LAYER SHEAR IS STILL FORECAST ALONG AND
    E OF SURFACE FRONT. THIS IN CONJUNCTION WITH STRONGER ISALLOBARIC
    FORCING INVOF SURFACE LOW MAY SUPPORT A FEW INTENSE STORMS WITH THE
    POTENTIAL FOR PRIMARILY DAMAGING WINDS.

    ...CNTRL/SRN PLAINS...
    MOIST LOW-LEVEL AIRMASS /CHARACTERIZED BY DEWPOINTS IN THE MID TO
    UPPER 60S/ IN COMBINATION WITH STEEP LOW TO MID-LEVEL LAPSE RATES
    WILL CONTRIBUTE TO A STRONGLY UNSTABLE AIRMASS THIS AFTERNOON S OF
    COLD FRONT AND E OF DRYLINE WITH MLCAPES INCREASING TO 2000-3000
    J/KG FROM CNTRL KS SWD INTO W-CNTRL TX. INITIATION OF DEEP MOIST
    CONVECTION WILL LIKELY OCCUR BY MID AFTERNOON ALONG SWD-MOVING COLD
    FRONT OVER PORTIONS OF NERN KS...WITH SUBSEQUENT DEVELOPMENT SWWD
    INTO PROGRESSIVELY STRONGER CAP OVER CNTRL INTO SWRN KS.

    WHILE STRONGEST MID AND UPPER-LEVEL WINDS WILL REMAIN OVER
    POST-FRONTAL AIRMASS...MODESTLY STRONG 500MB WINDS OF 35-45KTS WILL
    GRADUALLY SPREAD NEWD ACROSS NRN PORTION OF INSTABILITY AXIS. WHEN
    COMBINED WITH THE EXPECTED DEGREE OF INSTABILITY...A FEW SUPERCELLS
    CAPABLE OF VERY LARGE HAIL AND DAMAGING WINDS APPEAR LIKELY.
    ISOLATED TORNADO THREAT MAY TEND TO INCREASE EARLY THIS EVENING
    ACROSS S-CNTRL KS/N-CNTRL OK OWING TO STRENGTHENING LOW-LEVEL SHEAR
    ALONG AXIS OF DEVELOPING LLJ. UPSCALE EVOLUTION OF TSTMS INTO
    CLUSTERS/MCS IS ANTICIPATED TONIGHT AHEAD OF EJECTING NV/UT
    VORTICITY MAX. WITH DAMAGING WIND THREAT EXTENDING NEWD ACROSS ERN
    KS INTO W-CNTRL/NWRN MO.

    ADDITIONAL...MORE ISOLATED SEVERE STORMS WILL ALSO BE LIKELY IN
    POST-FRONTAL UPSLOPE REGIME OVER THE CO FRONT RANGE. WHILE
    INSTABILITY WILL REMAIN SOMEWHAT LIMITED WITH MLCAPES GENERALLY LESS
    THAN 1000 J/KG...STRONG VERTICAL WIND SHEAR WILL SUPPORT THE
    POTENTIAL FOR SUPERCELLS WITH LARGE HAIL.

    FINALLY...A COUPLE OF ISOLATED STORMS MAY DEVELOP SWD ALONG DRYLINE
    WHERE BOUNDARY-LAYER BECOMES SUFFICIENTLY MIXED TO OVERCOME CAP.
    THOUGH DEEP-LAYER SHEAR DECREASES WITH SWD EXTENT... POTENTIAL FOR
    SUPERCELL/ORGANIZED MULTICELL STRUCTURES WILL EXIST WITH LARGE HAIL
    AND DAMAGING WINDS BEING THE MAIN THREATS.

    ..MEAD/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.



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Duane Whittingham (N9SSN) - Producer
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