The presence of a jet stream passing over a mountain range tends to reinforce a mountain wave system that has developed at lower levels. This reinforcement provides the optimum conditions for the mountain waves to extend up to the level of the key stream.

A deep, stable layer combined with a consistent, strong, westerly flow at low level over a mountain range can result in a mountain wave system developing un to high level, when the decrease in air density with height is matched by a similar decrease in wind speed with height.

When winds from a consistent direction, approximately perpendicular to a mountain range or high plateau, increase in speed with height within a deep, stable layer, mountain waves and their effects can extend from low to high level.

A strong westerly airflow that increases in speed with height, when combined with a deep, unstable layer in the vicinity of a mountain range, can often result in the wave motion, and its associated turbulence, extending from low through to high level.