Overnight derecho worth watching

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Only a few hours into the forecast and already a wrinkle to be had.

A large complex of severe storms has formed to our north and west with numerous warnings for large hail and 70 mph winds. Thunderstorm complexs like this one are fast movers and can cover a lot of area in just 10 hours or so. This complex is moving to the east and southeast about 50 mph and is currently over northern Missouri. I think this has a shot of making into Kentucky around or shortly after dawn. This thunderstorm complex will likely weaken some but still could produce hvy rains, gusty winds near severe levels and hail. As of now I would say we have a 45% chance of being impacted by this thunderstorm complex for the morning rush.

radars

Upper Mississippi Valley sector loop

Central Great Lakes sector loop

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3 Responses to “Overnight derecho worth watching”

  1. mitchg Says:

    spc update for areas northwest of our region along the path of the mcs

    THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 242
    CONTINUES.

    QUASI-LINEAR CONVECTIVE SYSTEM OVER EXTREME SERN IA AND NRN MO
    EXTENDS WWD OVER KS BEHIND ITS OWN OUTFLOW…HOWEVER MAIN THRUST OF
    ASSOCIATED WIND POTENTIAL SHOULD EXTEND OVER PORTIONS ERN MO AND WRN
    IL DURING NEXT 3-4 HOURS. NEW WW MAY BE REQUIRED FOR LATTER AREAS.

    SFC MESOANALYSIS SHOWS BROAD AREA OF UPPER 60S TO LOW 70S F SFC DEW
    POINTS ACROSS ERN MO AND WRN IL. RELATIVELY RICH BOUNDARY LAYER
    THETAE HELPS TO STEM PACE OF DIABATIC SFC COOLING/STABILIZATION IN
    MODIFIED RAOBS AND MODEL SOUNDINGS…SUCH THAT MLCAPE WILL REMAIN IN
    2000-3000 J/KG RANGE AT LEAST UNTIL 08Z…WITH MLCINH UNDER 100 J/KG
    MOST AREAS. THIS SHOULD BE SUFFICIENT TO SUSTAIN POTENTIAL FOR SVR
    MCS TO PROCEED SEWD OUT OF EXISTING WW…CONTINUING DAMAGING WIND
    POTENTIAL ALONG LEADING PART OF ITS WELL-ORGANIZED/LONG-LIVED COLD
    POOL. FARTHER W…OUTFLOW BOUNDARY SHOULD CONTINUE TO REMAIN WELL
    AHEAD OF PRIMARY BAND OF RADAR REFLECTIVITY ACROSS NWRN MO AND KS.
    HOWEVER…TSTMS SHOULD BE MAINTAINED TO SOME EXTENT BY STG
    ISENTROPIC ASCENT TO LFC…GIVEN ONGOING/EXPECTED 40-50 KT LLJ
    MOVING ABOVE COLD POOL. LARGE HAIL REMAINS MAIN CONCERN WITH THAT
    TRAILING ACTIVITY.

    this says activity should be maintained through 4 am as it moves southeast with a new watch issued along it’s path. a watch for our region would come after 4 am more than likely.

  2. mitchg Says:

    that watch has now been issued for ILL.

    DISCUSSION…WELL-FORMED MCS WILL CONTINUE ESEWD FOR THE NEXT FEW
    HOURS WITH AN ATTENDANT THREAT FOR DAMAGING WINDS. A CONTINUATION
    OF MODERATE INSTABILITY AND RELATIVELY WEAK CONVECTIVE INHIBITION
    WILL HELP MAINTAIN THE CONVECTION AS IT CROSSES THE MS RIVER AND
    MOVES INTO WRN/CENTRAL IL.

  3. mitchg Says:

    heading to bed if a watch is issued i will be alerted by my weather radio and will put up a new post.

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