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    May 1st-2nd Storm

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    jdrenken
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    May 1st-2nd Storm

    Post  jdrenken on Sat Apr 26, 2008 9:13 pm

    Ok...I know that this has been posted on the other two forums, but didn't want y'all to think that I was ignoring the site. Wink

    St. Louis (LSX) AFD...

    WEATHER WILL BE TRANQUIL MID WEEK AS AN UPPER ZONAL FLOW IS FORECAST
    BY THE GFS AND ECMWF ACROSS THE AREA. BY THURSDAY MORNING, BOTH
    MODELS FORECAST A DEEP TROUGH/CLOSED LOW TO DIG INTO THE SOUTHERN
    ROCKIES. THE SURFACE LOW THAT DEVELOPS AS A RESULT LOOKS MORE LIKE
    EARLY MARCH THAN EARLY MAY.


    Lincoln (ILX) AFD...

    LONG TERM...WEDNESDAY THROUGH SATURDAY...
    STRONG WARM ADVECTION WILL COMMENCE ACROSS THE MID SECTION OF THE
    NATION WEDNESDAY AND THURSDAY AHEAD OF ANOTHER DEEP UPPER TROUGH
    THAT WILL MOVE INTO THE ROCKIES AND EVENTUALLY INTO THE PLAINS. LEE
    TROUGHING/CYCLOGENESIS WILL TAKE PLACE OVER THE LEE OF THE MOUNTAINS
    AND PROVIDE DEEP SOUTHWESTERLY FLOW...BUT IT WILL TAKE A COUPLE OF
    DAYS FOR ENOUGH MOISTURE TO MAKE IT BACK INTO THE MIDWEST AFTER
    BEING SHOVED SO FAR SOUTH INTO THE GULF BY THE EARLY-WEEK SYSTEM.
    THE GFS AND ECMWF HAVE BEEN FORECASTING WARM FRONTAL DEVELOPMENT
    SOUTH OF ILLINOIS AND PUSHING THIS FEATURE NORTH INTO THE REGION
    THURSDAY. BY THAT TIME...THE WESTERN TROUGH IS FORECAST TO EMERGE
    INTO THE PLAINS AND DRIVE THE NEXT LOW PRESSURE SYSTEM INTO THE
    MISSISSIPPI VALLEY AROUND FRIDAY. MODEL DIFFERENCES STILL EXIST ON
    THE EXACT EVOLUTION OF THE UPPER TROUGH AND TRACK OF THE ASSOCIATED
    SURFACE LOW...SO NOTHING MORE THAN CHANCE POPS ARE WARRANTED FOR NOW
    BASED ON LOW PREDICTABILITY. HOWEVER IT IS NOTABLE THAT NUMERICAL
    GUIDANCE BASED ON THE GFS MODEL...WHICH HAS A SIGNIFICANT WEIGHT
    TOWARD CLIMATOLOGY BY DAYS 6 AND 7...HAS POPS THAT ARE TWICE AS HIGH
    AS CLIMATOLOGY ON FRIDAY.

    centralplainsstorm
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    Re: May 1st-2nd Storm

    Post  centralplainsstorm on Sun Apr 27, 2008 6:25 pm

    cant wait for this one but as usual it depends on a lot!
    however, LIs are way negative, CAPE looks good, Cinh is eroding fast, time of day is looking favorable
    cheers

    Chicago Storm
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    Re: May 1st-2nd Storm

    Post  Chicago Storm on Sun Apr 27, 2008 9:36 pm

    Gotta wait and see, looks like the targe area for Thursday will be the plains. As for Friday, its a bit unclear but threat will push east.

    jdrenken
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    Updated SPC

    Post  jdrenken on Mon Apr 28, 2008 7:40 am

    Updated SPC Outlook...



    DAY 4-8 CONVECTIVE OUTLOOK
    NWS STORM PREDICTION CENTER NORMAN OK
    0342 AM CDT MON APR 28 2008

    VALID 011200Z - 061200Z

    ...DISCUSSION...
    MAJOR MID/UPPER LEVEL LOW -- NOW EVIDENT IN MOISTURE CHANNEL IMAGERY
    FROM GULF OF AK SWD ALONG 140W TO NEAR 40N -- IS FCST TO MIGRATE
    SEWD OVER NWRN CONUS AND SWRN CANADA THROUGH DAY-3...THEN REDEVELOP
    SEWD ACROSS CENTRAL PLAINS DAYS 4-5/1ST-3RD. BEGINNING ABOUT MIDDLE
    OF DAY-4...OR 02/00Z...CONSIDERABLE SPREAD BEGINS TO APPEAR BETWEEN
    OPERATIONAL MODELS AS SHORTWAVE DETAILS MORE STRONGLY IMPACT
    GEOMETRY OF SYSTEM AND SUBSEQUENT EVOLUTION. MREF GUIDANCE IS
    UNAVAILABLE...HOWEVER...STG CONSENSUS IS TAKING SHAPE AMONGST
    DETERMINISTIC ECMWF/SPECTRAL/UK PROGS REGARDING BASIC DAY-4 PATTERN
    -- STG MID/UPPER VORTEX ALOFT...DEEPENING THEN OCCLUDING SFC CYCLONE
    MOVING ACROSS PORTIONS NRN KS/ERN NEB...TRAILING COLD FRONT MOVING
    SEWD OVER SRN HIGH PLAINS...AND DRYLINE SSWWD FROM LOW ACROSS
    PORTIONS CENTRAL/ERN KS...CENTRAL OK...AND N-CENTRAL OR NW TX.
    RETURN FLOW MOISTURE MAY BE SUFFICIENT TO SUPPORT WIDESPREAD SVR
    POTENTIAL FROM NEAR AND E OF SFC LOW SWD TOWARD ARKLATEX/SE OK
    REGION. DEEP-LAYER LOW IS FCST TO OCCLUDE DEEPLY AND BEGIN FILLING
    DAY-5/2ND-3RD...WITH TOO MUCH PROG SPREAD FROM THEN ONWARD TO ASSIGN
    ADDITIONAL SVR-DAY AREAS.

    jdrenken
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    Re: May 1st-2nd Storm

    Post  jdrenken on Mon Apr 28, 2008 8:59 am

    Frank Straight just explained in his 7:45 pm Sunday blog one theory of why the UK and Euro models are slower than the GFS. There is a blocking situation over the Atlantic with a high pressure to the north of the low, which slows things down in the US. He states that the GFS usually doesn't realize how strong the blocking is going to be.

    Watch it here.

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    Re: May 1st-2nd Storm

    Post  Chicago Storm on Mon Apr 28, 2008 11:40 pm

    Looks like a 2 day out break (Thursday/Friday), though there are a lot of factors that still need to be worked out.

    jdrenken
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    Re: May 1st-2nd Storm

    Post  jdrenken on Tue Apr 29, 2008 6:35 am

    Day 2 Outlook...



    DAY 3 CONVECTIVE OUTLOOK
    NWS STORM PREDICTION CENTER NORMAN OK
    0231 AM CDT TUE APR 29 2008

    VALID 011200Z - 021200Z

    ...THERE IS A SLGT RISK OF SVR TSTMS ERN NEB/WRN IA SSWWD TO
    PORTIONS N-CENTRAL/NE TX...

    ...SYNOPSIS...
    BROAD MID/UPPER CYCLONE NOW OFFSHORE PACIFIC NW AND BC WILL SHIFT
    ESEWD ACROSS PACIFIC NW AND OVER MUCH OF CENTRAL/NRN ROCKIES BY
    1/12Z. LEAD SHORTWAVE TROUGH NOW OFFSHORE ORE SHOULD EJECT NWD
    ACROSS MT DAY-2 AND REINFORCE/MERGE WITH CYCLONE CORE OVER SRN AB BY
    START OF THIS PERIOD. MEANWHILE...VORTICITY LOBE -- NOW EVIDENT IN
    MOISTURE CHANNEL IMAGERY OVER GULF OF AK...IS FCST TO REVOLVE SWD
    THEN SEWD AROUND UPPER CYCLONE AND AMPLIFY CONSIDERABLY...REACHING
    CENTRAL ROCKIES OR CENTRAL HIGH PLAINS BY 2/00Z. MODEL
    INCONSISTENCIES DESCRIBED IN DAY-2 OUTLOOK WITH THIS SHORTWAVE
    TROUGH...AND WITH LOCATION OF ASSOCIATED SFC CYCLONE ALONG COLD
    FRONT...EXTEND INTO DAY-3 PERIOD...AND WILL AFFECT LOCATION/STRENGTH
    OF GREATEST SVR POTENTIAL.

    PRIND SFC LOW SHOULD LIFT NEWD ACROSS CENTRAL/N-CENTRAL KS EARLY IN
    PERIOD AND BE LOCATED SOMEWHERE OVER ERN NEB BY 2/00Z...WITH COLD
    FRONT TRAILING SWWD ACROSS S-CENTRAL/SERN KS...N-CENTRAL THROUGH
    W-CENTRAL/SW OK AND TX PANHANDLE. DRYLINE SHOULD INTERSECT FRONT
    INVOF N-CENTRAL OK AND EXTEND SSWWD ACROSS PARTS OF CENTRAL/SRN OK
    AND N-CENTRAL/NW TX. COLD FRONT SHOULD OVERTAKE DRYLINE OVERNIGHT
    AND MOVE EWD INTO MO...AND SEWD ACROSS ERN OK AND WRN/NRN TX.

    ...CENTRAL/SRN PLAINS...LOWER MO VALLEY...
    SOMEWHAT TIGHTLY CLUSTERED SVR OUTBREAK IS POSSIBLE -- INCLUDING
    SUPERCELLS WITH LARGE/DAMAGING HAIL AND POSSIBLY SIGNIFICANT
    TORNADOES. ATTM...CONSENSUS OF SREF AND OPERATIONAL PROGS INDICATES
    PORTIONS ERN KS...NERN OK...AND WRN MO MAY HAVE MAXIMUM OVERALL
    POTENTIAL. HOWEVER...NON-TRIVIAL THREAT EXTENDS NWD TOWARD SERN
    NEB/SRN IA/NRN MO AND SWD OVER ERN OK/NWRN AR. UNCERTAINTIES
    PRECLUDING GREATER PROBABILITIES ATTM INVOLVE TRACK/INTENSITY OF SFC
    LOW AND RELATED LOW LEVEL FORCING...NWD EXTENT OF MOST FAVORABLE
    RETURN FLOW MOISTURE...AND CAPPING ALONG/AHEAD OF DRYLINE OVER ERN
    OK AND RED RIVER REGION. AS SOME OF THESE MESOSCALE DETAILS BECOME
    BETTER RESOLVED...CATEGORICAL RISK UPGRADE IS POSSIBLE FOR THIS FCST
    PERIOD.

    STRONGER DEEP-LAYER FORCING IS FCST TO LIFT NEWD ACROSS LOWER MO
    VALLEY REGION DURING DAY...WITH EARLIER INITIATION OF STG-SVR TSTMS
    LIKELY THAN FARTHER S WHERE SBCINH WILL BE STRONGER AND LOW LEVEL
    CONVERGENCE SOMEWHAT WEAKER. NRN PORTION OUTLOOK INCLUDES
    CONDITIONAL POTENTIAL OF RELATIVELY SMALL/LOW-TOPPED SUPERCELLS WITH
    TORNADOES AND HAIL JUST NE-E OF SFC LOW. FARTHER S...LARGE
    LOW-MIDLEVEL LAPSE RATES...STRONGER CAPPING...GREATER LOW LEVEL
    MOISTURE AND STRONGER HEATING WILL CONTRIBUTE TO SOMEWHAT MAXIMIZED
    POTENTIAL FOR DISCRETE....WIDELY SCATTERED TO ISOLATED DEVELOPMENT
    OF SUPERCELLS WITH POTENTIAL FOR SIGNIFICANT SEVERE OVER ERN OK AND
    SERN KS. DEVELOPMENT FARTHER S TOWARD N-CENTRAL TX BECOMES
    PROGRESSIVELY MORE CONDITIONAL...ESPECIALLY BEFORE DARK. BAND OF
    SVR TSTMS SHOULD EVOLVE BY AROUND 02/06Z FROM MO SWWD ACROSS ERN
    OK/WRN AR AND PERHAPS NE TX...WITH THREAT EVOLVING MORE TOWARD
    DAMAGING WIND...BUT WITH TORNADOES AND HAIL STILL POSSIBLE.

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