Everything you needed to know about snow

Ever wondered about the difference between a blizzard and a snow squall? CBC News offers a compendium of defintions and interesting facts about winter weather, including everything you'll ever need to know about snow.

From snow grains to freezing rain, blizzards to snow squalls

Canadians are no strangers to winter weather and have developed quite the lexicon to describe the various snowy conditions experienced across the country. (Graham Hughes/Canadian Press)

It's just falling ice composed of crystals in complex hexagonal forms — a major part of Canadian life between November and early April. Unless, of course, you live in Victoria or Vancouver, where the mild Pacific is usually enough to ward off the white stuff.

So what is this substance that so consumes Canadians? Snow forms in clouds when water vapour turns directly to ice without going through the liquid stage.

We've developed quite the lexicon when it comes to the white stuff, but not quite the myth of the 400 words the Inuit allegedly have for snow. English or Inuktitut, there really are only a couple of dozen ways to describe snow — and the various ways it tests our patience.

Here's a quick guide to snow in Canada — and how to prepare for it.

Snow grains, freezing rain, sleet

While purchasing up your morning coffee, you overhear the following conversation:

"I hear it's gonna snow today."

"Yup, we're getting some snow."

Here, the term snow is used without qualification. It means you can expect precipitation of significant duration and extent. Try to remember where you put your snow shovel.

Had the snow-concerned people said "we're expecting snow flurries or snow showers," you would have breathed a bit of a sigh of relief, because you knew that not much of the white stuff would accumulate — at least not enough to shovel.

You would have been even less concerned had they used the term snow grains — although very few of us do in normal conversation. Snow grains are very small ice crystals or the ice equivalent of drizzle. Not much to worry about — but you might have to scrape the windshield of your car a little.

One stage up is snow pellets, which are white, opaque particles that form as ice crystals fall through cloud droplets that are below freezing but still liquid. The cloud droplets freeze to the crystals forming a small lumpy mass — not the multi-pointed crystals of ice that make up snowflakes. They are usually easy to shovel.

Among the nastiest stuff winter has to offer is sleet. This is formed when drops of rain or drizzle freeze into ice as they fall. Sometimes called ice pellets, these things sting when accompanied by a strong wind.

Even worse is freezing rain or drizzle. These water droplets maintain a temperature below 0 C but do not turn to ice in the air. But they freeze as soon as they hit anything on the ground. This can lead to much scraping of your car's windshield and slipping and sliding on sidewalks.

Ice crystals are tiny sprinkles that sparkle in the sunshine and hang in the air — usually when it's really, really cold out.

Blowing snow vs. drifting snow

Snowstorms are a fact of life in Canada — and they can vary, depending on where you live.

Good old-fashioned blizzards, for instance, are rare in most of the country. They are snow storms with reduced visibility due to blowing or falling snow with high winds and must last at least four hours, at least in most of Canada. In the North, it must last six hours.

On Jan. 30, 1947, southern Saskatchewan was inundated with a series of blizzards that lasted 10 days. The storm blocked all highways in Regina and buried a train under a snowdrift that was one kilometre long and eight metres deep.

Thought that blowing snow and drifting snow were the same thing? There's an important distinction between the two. Blowing snow is lifted by the wind from the earth's surface to a height of two metres or more. Drifting snow is blown to a height of less than two metres. So if your head's poking out of a mound of snow and you're a little taller than two metres, it's drifting snow that got you.

Lake effect snow is most common near the Great Lakes. These squalls occur as cold air picks up substantial moisture as it moves over the lakes. The moisture gets dumped as snow inland from the downwind shore. Usually, they follow major storm systems that are cleared out of the area by blasts of Arctic air.

Often the affected region will get a much bigger dump of snow from the squall than from the storm itself. In the more severe lake-effect snow squalls, accumulations of more than 75 centimetres per day are not uncommon, and fall rates as high as 28 centimetres per hour have been reported. Such severe snowfalls have been termed snowbursts.

These nasty little storms are often confined to small geographical areas. It could be snowing like crazy over your house — but bright and sunny (but really cold) a few kilometres away.

They may have some of the same characteristics, but there are some major differences between blizzards and snow squalls.

In a blizzard:

  • Winds must be sustained at 40 km/h.
  • Visibility from blowing and/or falling snow is 400 metres or less.
  • The above conditions must be met for a minimum of four hours in most of Canada and at least six hours in the North.
  • You do not have to have snow falling.

In a snow squall:

  • Snow must be falling, at least 15 centimetres or more in 12 hours or less.
  • Visibility must be reduced to 400 metres or less due to heavy snow, with or without blowing snow, for three hours or more.

Yet another type of storm is sometimes called an Alberta clipper. This is a fast-moving winter storm that forms just east of the Rockies and sweeps south and eastward across southern Canada and the upper Midwest states. They're usually weaker than most winter storms and don't usually drop much snow. But they often bring along their evil twin — a surge of frigid Arctic air that can produce near-zero visibility in blowing and drifting snow.

Snowfall, winter storm warnings

There are various levels of warnings you will receive from your local weather forecaster. Pay attention, because there are significant differences between them. As explained above, a blizzard and a snow squall are different weather events.

When you hear a snowfall warning, you can expect a healthy dose of the white stuff. At least 15 centimetres over the course of 12 hours in the Atlantic provinces, Quebec, Ontario and parts of British Columbia.

For Alberta, Saskatchewan, Manitoba, Northwest Territories, Nunavut and parts of Yukon and British Columbia, you can expect to receive at least 10 centimetres of snow in 12 hours or less.

Sections of the southern and central coasts of B.C. can get snowfall warnings for just five centimetres of snow with six hours or less.

Travel could become hazardous if plenty of snowfall is expected, unless the plows get a good jump on the situation.

Environment Canada issues a winter storm warning if conditions are favourable for the development of severe winter conditions including a blizzard, major snowfall of 25 centimetres or more with a 24-hour period or significant snowfall combined with freezing rain, strong winds, blowing snow or extreme wind chill.

Winter storms and excessive cold claim more than 100 lives every year across the country, according to Environment Canada.