A22. Formed when strong winds moving across mountains set up a wavelike action in
the winds downstream from the mountain. The upward moving air in the waves, if
moist, is brought to saturation as it rises.
Formed when moist air is forced upward by a mountain top and dissipates on the
leeward side of the mountain as the moving air descends.
A24. In eighths of the sky.
A25. Clouds and/or obscuring phenomena aloft either continuous or composed of
detached elements that have bases at approximately the same level.
A26. The lowest layer that blocks 5/8 ormoreofthe celestial dome from beingseen.
A27. Any collection of atmospheric phenomena dense enough to obscure even the
portion of the sky directly overhead.
A28. Sky cover at any level is equal to the amount the sky cover of the lowest layer plus
the additional sky cover present at all successively higher layers (up to and
including the layer being considered).
A29. 12,000 feet.
A30. 7,500 feet.
A31. Prevailing visibility, sector visibility, differing level (or tower) visibility, and
runway visual range.
A32. The greatest distance that known objects can be seen and identified throughout
half or more of the horizon circle.
A33.Combat Information Center (CIC).
When it differs from the prevailing visibility, and either prevailing visibility or
sector visibility is less than 3 miles.
When the prevailing visibility is 4 miles or less.
A37. In desert regions on calm, hot, clear afternoons.
A38. Blowing sand that reduces visibility to less than 5/16 of a mile.
Water vapor bypasses the liquid state and goes directly from a gas to a solid.
A40. Moisture, hygroscopic nuclei, and cooling.
A41. Four Celsius degrees or less.
A42. Advection fog.