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The international definition of fog is a visibility of less than 1 km (3,300 ft); mist is a visibility of between 1 km (0.62 mi) and 2 km (1.2 mi) and haze from 2 km (1.2 mi) to 5 km (3.1 mi). Fog and mist are generally assumed to be composed principally of water droplets, haze and smoke can be of smaller particle size.
Blowing snow [1] is snow lifted from the surface by the wind, at eye level (1.8 m or 6 ft) or more, [2] that will reduce visibility. Blowing snow can come from falling snow or snow that already accumulated on the ground but is picked up and blown about by strong winds.
Whiteout or white-out [1] is a weather condition in which visibility and contrast are severely reduced by snow, fog, or sand. The horizon disappears from view while the sky and landscape appear featureless, leaving no points of visual reference by which to navigate.
A blizzard is a severe snowstorm characterized by strong sustained winds and low visibility, lasting for a prolonged period of time—typically at least three or four hours. A ground blizzard is a weather condition where snow that has already fallen is being blown by wind.
Visibility is reduced by falling snow, and this is further exacerbated by strong winds which are commonly associated with winter storms producing heavy snowfall. In extreme cases, this may lead to prolonged whiteout conditions in which visibility is reduced to only a few feet due to falling or blowing snow. These hazards can manifest even after ...
The U.S. government's road safety agency is investigating Tesla's “Full Self-Driving” system after getting reports of crashes in low-visibility conditions, including one that killed a pedestrian.
By definition, fog reduces visibility to less than 1 km (0.62 mi), whereas mist causes lesser impairment of visibility. [4] For aviation purposes in the United Kingdom, a visibility of less than 5 km (3.1 mi) but greater than 999 m (3,278 ft) is considered to be mist if the relative humidity is 95% or greater; below 95%, haze is reported.
Reduced visibility less than 400 m (0.25 mi), caused by snowfall, with or without blowing snow, for 3 hours or more. Frontal – Issued when conditions are favourable for the development of snow squalls that produce brief periods of very poor visibilities caused by heavy snow and blowing snow caused by the passage of a cold front.