What process results in the formation of orographic fog (hill fog)?

Question

PPL(A) English - Private Pilot License (Aircraft) - Meteorology - What process results in the formation of orographic fog (hill fog)?

QuizVDS · Accepted Answer

Warm, moist air is moved across a hill or a mountain range

QuizVDS · Answer

Prolonged radiation during nights clear of clouds

QuizVDS · Answer

Cold, moist air mixes with warm, moist air

QuizVDS · Answer

Evaporation from warm, moist ground area into very cold air

PPL(A) EN: What process results in the formation of "orographic fog" ("hill fog")?