Aviation Forecast Discussions Data
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(EXTRACTED FROM FXUS63 KLOT 031512)


    
    For the 12Z TAFs...
    
    Main concerns through the TAF period:
    
    * Timing and coverage of thunderstorms this morning into early
    afternoon
    * Convective influence of wind directions and gusts this morning
    * Lake breeze timing this afternoon
    
    A narrow east-west oriented axis of showers and thunderstorms
    continues to drift east southeast across northern Illinois this
    morning. Plenty of uncertainty remains with how things will unfold
    even within just the next few hours. Have added a VCTS mention to
    start the TAF at ORD and MDW to account for the persistent
    lightning embedded in the thunderstorm cluster moving east across
    northern Illinois.
    
    Hi-res model guidance continues to indicate additional
    thunderstorm development will try to develop along the I-80
    corridor by mid morning, so have maintained the TEMPO TSRA from
    16-18Z for ORD & MDW to account for this potential. However,
    confidence in this remains low. Winds then turn northwesterly
    behind the front as it moves through. Any lingering thunderstorms
    are expected to drop south of area terminals by 19-20Z.
    
    A lake breeze is also expected this afternoon, the exact timing
    of which may be complicated somewhat by any resultant thunderstorm
    outflows. Once it is able to push through, winds will turn
    northeasterly to near easterly across the Chicago area terminals
    this afternoon. Winds become mostly light and variable area wide
    this evening through tomorrow morning.
    
    Petr