Fog at airports has a major impact on aviation operations worldwide, affecting both safety and economics. Fog is often not captured adequately by numerical weather prediction (NWP) models due to the complex interaction between elements at a range of spatial and time scales involved in the fog processes. The Bureau of Meteorology uses the Australian Community Climate and Earth-System Simulator (ACCESS) for NWP guidance and this is progressively upgraded as the science improves and computational upgrades allow.  The ACCESS model includes fog fraction and visibility as a standard diagnostic output; however, the visibility guidance has been quite poor and had limited value to forecast operations. The shortcomings in the predicted visibility are due to limitations of the diagnostic visibility scheme and to inaccuracies in the meteorological fields predicted by the NWP model.  Work was undertaken to isolate the visibility scheme from the model and perform a variety of sensitivity and tuning experiments to better understand its performance in Australian conditions. Based on results from the experiments, a new set of configuration parameters providing improved forecasts of visibility has been implemented in the ACCESS model.  The ACCESS model has recently been upgraded to the Australian Parallel Suite 3 (APS3) and for the first time this also includes the implementation of global and city-scale ensemble models for Australia.  This will enable a better understanding of model uncertainties and forecast probabilities.  The talk will present details on the improvements in forecast guidance for fog and explore the use of ensembles.