Blizzard

Unique identifier / Notation

MH0034

Synonyms

In Russia ‘purga’ or ‘metel’

Snow storm.

A blizzard is a severe snow storm characterised by poor visibility, usually occurring at high-latitude and in mountainous regions (WMO, 1992).

Primary reference(s)

WMO, 1992. International Meteorological Vocabulary, WMO-No. 182. World Meteorological Organization (WMO). Accessed 18 November 2019.

Additional scientific description

The term blizzard is generally used in North America and Great Britain. There are differing thresholds for defining and issuing warnings for blizzards.

Metrics and numeric limits

Thresholds for defining and issuing warnings for blizzards vary by country.

In the USA, a blizzard warning is issued for winter storms with sustained or frequent winds of 35 mph (56 km/hr) or higher with considerable falling and/or blowing snow that frequently reduces visibility to 1/4 of a mile (0.4 km) or less. These conditions are expected to prevail for a minimum of 3 hours (Eye on the Sky, no date).

In the UK, a blizzard is defined as moderate or heavy falling snow (either continuous or in the form of frequent showers) with winds speeds of 30 mph (48 km/hr) or more and a reasonably extensive snow cover reducing visibility to 200 metres (0.13 miles) or less (UK Met Office, 2019).

In Canada, alerting parameters for issuing a blizzard warning include when winds of 40 km/hr or more are expected to cause widespread reductions in visibility to 400 metres (0.25 miles) or less, due to blowing snow, or blowing snow in combination with falling snow, for at least 4 hours. North of the tree line the thresholds are the same as the national thresholds except when conditions are expected to last for at least 6 hours (Government of Canada, no date).

Key relevant UN convention / multilateral treaty

Not applicable.

Examples of drivers, outcomes and risk management

A blizzard is severe winter weather characterised by strong winds, and heavy or blowing snow that causes low to zero visibility. In whiteout conditions associated with blizzards people have become lost even when going only short distances (Environment and Climate Change Canada, no date).

Winter storms create a higher risk of car accidents, hypothermia, frostbite, carbon monoxide poisoning, and heart attacks from overexertion, etc. To avoid these risks, the warnings and preventative instructions from local and national authorities should be followed.