Blowing snow Wind driven snow that reduces visibility to six miles or less causing significant drifting. Blowing sand Sand particles picked up from the surface of the earth by the wind to moderate heights above the ground, reducing the reported horizontal visibility to less than seven statute miles. Visibilities of 1/8 mile or less over a widespread area are criteria for a Blowing Dust Advisory. Blowing Dust Dust that is raised by the wind to moderate heights above the ground to a degree that horizontal visibility decreases to less than seven miles. It blocks the movement eastward movement of low pressure areas (cyclones) at its latitude. Blocking high A high pressure area (anticyclone), often aloft, that remains nearly stationary or moves slowly compared to west-to-east motion. In Australia, it is described as a violent and very cold wind which is loaded with snow, some of which has been raised from snow covered ground.
In Canada, a blizzard described as a severe storm that lasts three or more hours, and brings low temperatures, strong winds and poor visibility due to blowing snow. Extremely cold temperatures often are associated with dangerous blizzard conditions. Blizzard Includes winter storm conditions of sustained winds or frequent gusts of 35 mph or more that cause major blowing and drifting of snow, reducing visibility to less than one-quarter mile for 3 or more hours.
Black ice Thin, new ice that forms on fresh water or dew covered surfaces it is common on roadways during the fall and early winter and appears "black" because of its transparency. Bitterly cold In winter, bitterly cold or very cold, refers to more than seven degrees Celsius below normal. Barometric pressure The actual pressure value indicated by a pressure sensor. Barometer An instrument for measuring atmospheric pressure. The structure typically is most pronounced on the leading edge of the updraft, while drier air from the rear flank downdraft often erodes the clouds on the trailing side of the updraft. Barber pole A thunderstorm updraft with a visual appearance including cloud striations that are curved in a manner similar to the stripes of a barber pole.
Top Ball lightning A relatively rarely seen form of lightning, generally consisting of an orange or reddish ball of the order of a few cm to 30cm in diameter and of moderate luminosity, which may move up to 1 m/s horizontally with a lifetime of a second or two. Business Date to Date (exclude holidays).