Aviation Forecast Discussions Data
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(EXTRACTED FROM FXUS61 KILN 121719)


    
    VFR conditions to start the 18Z terminal forecast with higher
    impact MVFR and likely IFR conditions in the last 6-9 hours of
    the forecast. Several waves of mid/high cloud will continue to
    spread across the TAF sites this afternoon as southerly winds
    gusts at times toward 20kts before the boundary layer decouples
    around 20Z. Will still see 6-10kts of southerly flow through the
    evening when a weak surface boundary attendant to the wave
    moving across the Great Lakes enters and begins to stall/wash
    out in the I-70 corridor later in the evening and overnight. In
    this timeframe, with increased convergence /albeit weak/ and
    moisture flowing in - expect a band or several bands of low
    stratus to form along or immediately behind what remains the
    front. Some guidance /HREF...NAM etc/ are very bullish on
    development of dense fog with time...but most other guidance is
    hinting stronger at a thick/low IFR ceiling developing and
    spreading across the area with some visibility reductions, but
    not to the degree of the NAM/HREF. Will continue the previous
    forecast cycle and indicate low ceilings /IFR/ developing by
    10-12Z and thickening/lowering with 4-5SM visibilities. There is
    concern given forecast soundings that an area of lower
    visibilities will exist - around 1-2SM. Confidence is low in
    this happening - but it is worth mentioning. Given depth of the
    moisture overall is quite shallow, do not expect precipitation
    to develop until later in the day when drizzle may need to be
    inserted in the CVG TAF on Thursday afternoon. Not enough
    confidence to do that yet, but will need to be watched.
    
    OUTLOOK...MVFR/IFR conditions will be possible at times from
    Thursday through Saturday.