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c. Waves not only reach great altitudes, but they also sometimes extend as far as a
hundred miles horizontally downwind from the line of mountains. These waves of air are
referred to as standing waves or mountain waves. They are characterized by standing
lenticular altocumulus and/or rotor clouds when sufficient moisture is available. These clouds
may form as long lines which are called standing wave clouds.

d. Reports of turbulence in waves may range from none to extreme, but usually
moderate to severe turbulence will be encountered. The most dangerous characteristic of
the standing wave airflow is that the updrafts and downdrafts can be very strong and extend
great distances upward or downward.