FAA Flight Instructor Airplane (FIA)Weather and Weather ServicesMedium
A pilot flying near a mountain range observes clouds forming and building on the windward side of the ridge, while the leeward side remains clear with warm, dry, gusty winds. What phenomenon best explains this observation?
- AOrographic lifting and downslope chinook winds
- BOccluded frontal lifting
- CAdvection fog formation
- DRadiation fog dissipation
Show answer & explanationAnswer & explanation
Correct answer: A. Orographic lifting and downslope chinook winds
As moist air is forced up the windward side of a mountain (orographic lift), it cools and condenses into clouds; after crossing the ridge, the air descends on the leeward side, warming adiabatically and drying out, producing the warm, gusty chinook (foehn) wind effect.
Why the other options are wrong
- B. Occluded fronts are large-scale synoptic features, not localized terrain effects.
- C. Advection fog results from warm moist air moving over a cold surface, not terrain lifting.
- D. Radiation fog forms from surface cooling at night, unrelated to terrain lifting.
Orographic Lift
The forced ascent of air as it flows over rising terrain, causing cooling, condensation, and cloud formation on the windward side; descending air on the leeward side warms and dries, sometimes producing chinook winds.
- Windward side: clouds, precipitation, turbulence
- Leeward side: clear skies, warm/dry downslope winds
- Can create severe turbulence and mountain wave activity downwind
Memory trick: Up the mountain: clouds form. Down the mountain: air warms.