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Snowsquall warning is a bulletin issued by Environment Canada's Meteorological Service of Canada to warn population of two types of snow events reducing visibilities in blowing snow: Lake effect snowsqualls and Frontal snowsqualls.
Lake effect snowsqualls are generated by cold arctic air moving over unfrozen water of lake or sea. These will reduce visibilities to less than 1 km and produce large accumulations of snow on the ground along narrow corridors in lee of the waters. Duration of these events can extend for days.
Frontal snowsqualls are associated with a fast moving intense cold front in winter. Visibilities must be reduce to less than 500 m, wind over 40 km/h with a wind shift. Quantities of snow is not important with this type but intensity is heavy for a short period, typically 10 to 20 minutes.