This research looks into the effect of forecast extension on the overall seasonal adjustment filter. Weights for the overall adjustment filter were generated for series extended by forecasts of the airline model derived with different values of the nonseasonal and seasonal MA parameters. This paper will focus on the adjustment filter for the concurrent adjustment, which refers to the adjustment of the most recent observation in the series. Details on how the filters vary for length of forecast, choice of model parameters, and choice of seasonal filter are given.