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How do mountain valleys increase wind speeds?

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A car drives along the Trans-Canada Highway with Mount Sir Donald's sharp, snow-capped peak rising above forested slopes in the Selkirk Mountains, British Columbia. — mountain Mount Sir Donald in the Selkirk Mountains, British Columbia, looms above a segment of the Trans-Canada Highway.

Mountain valleys can increase wind speeds through a process known as "funneling," where the topography constricts regional airflows, forcing them to accelerate as they pass through the confined space.1

In addition to this mechanical effect, valleys are central to the development of local wind systems driven by temperature differences:

Mountain and Valley Breezes: During the day, solar heating of sunlit slopes causes air to rise, creating an anabatic flow that moves upslope. At night, the process reverses as cooling slopes cause air to drain downward, resulting in katabatic flow. These winds can range from gentle breezes to strong gusts depending on the specific configuration of the terrain.2
Foehn Winds: When air is forced over a mountain barrier, it undergoes adiabatic temperature changes. As the air descends on the leeward side, it warms and can reach high velocities, sometimes exceeding 185 kilometres (115 miles) per hour.2

These interactions between mountain slopes and valley floors create complex microclimates that significantly influence local wind patterns.1