Australia usually sees a specific type of fog called radiation fog which forms overnight and often just prior to or at sunrise. As we move into winter these fine water droplets suspended in the air will become more common. Clear skies, light winds and humid air are the most favourable conditions for this fog to form. As soon as the sun rises, solar heating and or an increase in wind speed generally clear the fog layer. On Good Friday morning, thick fog in the NSW Riverina dropped visibility to less than 25 metres. In Sydney, Richmond's visibility dropped down to 100 metres but cleared shortly after sunrise. A broad high pressure system over South Australia extended a ridge over New South Wales, causing the morning fog. Clear skies and light winds allowed the ground to loose heat. Moist air then moved over the ground and cooled to its saturation point, allowing moisture to condense and fog to form. The high is expected to move into the Tasman Sea by Sunday and become semi-stationary. On Saturday and Easter Sunday, patchy early fog is likely in VIC and NSW but won't be long lasting.