Orographic lift - As moist air rises over mountains, it cools and condenses to form clouds. If the temperature drops enough, the water droplets in the clouds will become liquid water and fog will form.

Adiabatic cooling - As air rises, its temperature decreases. This is because the air pressure is lower at higher altitudes, and when air expands it cools. As the air cools, the water vapor in the air condenses to form clouds and fog.

Convergence - When air converges (comes together) it creates an area of high pressure. This high pressure causes the air to sink, which in turn causes the air to warm and the clouds or fog to dissipate. Conversely, when air diverges (moves apart) it creates an area of low pressure. This low pressure causes the air to rise, which in turn causes the air to cool and the clouds or fog to form.