In order to improve the forecasting of fog, visibility and drizzle within the Met Office Unified Model, three parametrizations are included in high-resolution, limited-area versions of the model. These are (i) improved rainfall speeds; (ii) linking aerosol to the autoconversion scheme; and (iii) a taper curve for cloud droplets near the surface. The results show a better representation of low-visibility conditions in winter. There is a general reduction in drizzle and a better representation of drizzle depending on whether the air mass is clean or polluted. Summertime occurrences of fog are also reduced and are now under-forecast, which will require a further investigation to correct. The package described in the paper has been made operational in the 4 and 1.5 km operational forecast versions of the Unified Model during the spring and summer of 2011, showing an improvement in model performance and a reduction in model error. This demonstrates the ability to improve operational NWP forecasts by coupling cloud and aerosol processes. Copyright © 2012 British Crown copyright, the Met Office. Published by John Wiley & Sons Ltd.