What is the primary characteristic of upslope fog?

The primary characteristic of upslope fog is that moist air is forced up mountain slopes. This phenomenon occurs when air that is humid and relatively warm is lifted as it encounters elevated terrain. As the air rises, it cools and reaches its dew point, leading to condensation and the formation of fog. This type of fog is typically observed in hilly or mountainous regions where the topography plays a significant role in shaping weather patterns.

The conditions that create upslope fog are quite specific; this fog tends to occur when there is sufficient moisture in the air and a lifting mechanism, like a mountain slope, that facilitates the cooling needed for fog formation. Other factors such as temperature and pressure can also influence the development and duration of this fog, reinforcing the importance of topography in creating it.