Lenticular Cloud

A stationary, lens-shaped or almond-shaped cloud that forms on the lee side of mountains when stable air is forced upward by terrain, creating standing mountain waves. Lenticular clouds are a strong visual indicator of mountain wave activity and can signal severe to extreme turbulence, strong updrafts and downdrafts, and rotor turbulence at lower levels. Pilots should avoid flying near lenticular clouds, as the associated turbulence can exceed the structural limits of light aircraft.