The winter storm warning issued for much of southern Alberta Saturday is now upgraded to a blizzard warning, according to Environment Canada.

Blizzard conditions will develop Sunday evening and into Monday as an intense storm moves through Alberta. Parts of northern Alberta have already seen heavy snow begin to fall, and that is expected to spread to southeastern Alberta by Monday afternoon.

The majority of the snow is expected to fall from midnight Tuesday and continue over the next 24 hours.

'It will be the biggest snowstorm of the season.' - Jodi Hughes, CBC Calgary weather specialist

While most areas are expecting 10 to 20 centimetres of snow, some could get walloped with as much as 30 centimetres by Tuesday morning.

Calgary is expected to have 16 cm of snow.

"It will be the biggest snowstorm of the season," said CBC weather specialist Jodi Hughes. "What we're watching for is an Arctic cold front that's developing [and] going to track down across the province and it's bringing with it an incredible amount of snow."

Environment Canada says the storm system will bring cold Arctic air on Monday, and winds gusting above 60 kilometres per hour will produce blizzard conditions in areas east of the Foothills.

The areas currently under a blizzard warning are:

  • Airdrie - Cochrane - Olds - Sundre
  • Brooks - Strathmore - Vulcan
  • City of Calgary
  • Cypress Hills Provincial Park - Foremost
  • Drumheller - Three Hills
  • Hanna - Coronation - Oyen
  • Lethbridge - Taber - Milk River
  • Medicine Hat - Bow Island - Suffield
  • Okotoks - High River - Claresholm
  • Red Deer - Ponoka - Innisfail - Stettler

​The majority of Alberta is currently under either a blizzard, winter storm or snowfall warning.

Blizzard vs. Winter storm warning

The upgrade of a winter storm warning to a blizzard warning sparked questions on social media sites like Twitter about the difference between the two alerts. To help clarify, here are the thresholds for each as defined by Environment Canada.

  • A blizzard warning is declared when winds of 40 kilometres per hour or greater are expected to cause widespread reductions in visibility to 400 metres or less due to blowing snow, or blowing snow in combination with falling snow, for at least four hours. 
  • A snowfall warning in Alberta is declared when 10 centimetres of more of snow falls within 12 hours or less.
  • A winter storm warning is declared when severe and potentially dangerous winter weather conditions are expected, including
    • A major snowfall (25 centimetres or more within a 24 hour period); and
    • A significant snowfall (amounts meeting the criteria for a snowfall warning) combined with other cold weather precipitation such as freezing rain, strong winds, blowing snow and/or extreme wind chill.

Blizzard conditions may be part of an intense winter storm, in which case a blizzard warning is issued instead of a winter storm warning.

Source: Environment Canada