Whiteout (weather) - Types

Types

There are four different forms of a whiteout:

1. In blizzard conditions, snow already on the ground can become windblown, reducing visibility to near zero.
2. In snowfall conditions, the volume of snow falling may obscure objects reducing visibility to near zero. This only happens during lake-effect snow, or mountain-effect snow, where the volume of snow can be many times greater than normal snows or blizzards.
3. In clear air conditions, when there is little or no snow falling, but the ground is completely covered with snow, diffuse lighting from overcast clouds may cause all surface definition to disappear. It becomes impossible to tell how far away the snowy surface is. In polar regions this optical illusion can make whole snow-covered mountains invisible against the background white cloud, and the horizon cannot be identified, slopes cannot be judged for steepness, and snow surfaces cannot be seen. This effect is exacerbated by a smooth surface of fresh snow. It is only when a contrasting object is placed on a snowy surface that the surface can be detected. In less extreme cases, it may suffice to break the snow surface by throwing a snowball ahead. This form is also known as flat light or sector whiteout.
4. Where ground-level thick fog exists in a snow-covered environment, especially on open areas devoid of features.