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

Question

Question PPL(A) - Private Pilot License - Meteorology

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

Id 63 - PPL(A) EN - What process results in the formation of "orographic fog" ("hill fog")?