Atmosphere And Weather

Understanding what Blizzard Conditions are



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It's hard to imagine a blizzard if you've never experienced one. During the blizzard of 1977, roads and cities shut down for hundreds of kilometres in every direction. The snow just wouldn't stop falling. Young children were pushed off their feet and pinned against fences by fierce winds that just wouldn't let up. Schoolbuses were trapped right on the road while snowdrifts closed in around them. More than 100 people died.

Snow and wind

Officially, a blizzard is just a very strong snow storm in which heavy snow is accompanied by winds strong enough to reduce visiblity. The windspeed has to be at least 40 kilometres per hour, or 35 miles per hour in the US.

In Canada, that means at least a quarter-metre of snow is falling from the sky every 24 hours, and it's usually much more. The blizzard of 1977 lasted for four days!

On top of that, any snow already on the ground is being whipped into large drifts by the strong winds. Those kinds of drifts can bury a house in no time. Some of the drifts during the 1977 blizzard were deep enough to bury overhead power lines. Over 2,000 children were trapped in their schools. Snowmobilers searching for lost schoolbuses went right overtop of them without realizing it!

At the same time, the blizzard wind's strong enough to really pack together that snow and turn it into solid masses of ice. Once that gets entrenched, you can't clear it off the street anymore with regular city snowplows.

Some people along the Lake Erie lakeshore even remember a wall of white coming at them, like one of those huge desert sandstorms but with snow instead. That wall of snow was all the powder snow on top of Lake Erie ice, whipped into the air by the high winds and blasted toward everything downwind.

Temperature and windchill

Temperature and windchill values aren't used anymore to officially classify a blizzard. That's not to say it won't be bitterly cold in the wind! The combination of freezing temperatures plus blizzard-level winds always creates wind chills of at least -18 degrees Celsius, even when the temperature outside the wind is only just below freezing.

Of course, the temperature in a blizzard's usually a lot lower than that. If you're standing outside and you're not wearing good winter clothing over every part of your body, your exposed skin will begin to freeze in minutes. It's a really good idea to stay out of the wind during a blizzard!

Size

People who've just been through Hurricane Sandy have some idea how big a blizzard can get. It's not just a few acres of snow. The blizzard of 1977 hit New York and Southwestern Ontario the hardest. In most of those areas, nothing was moving after the first day except snowmobiles.

Even that wasn't the end of this blizzard's reach. Before it was done, there was snow falling from the sky in Miami. The Florida orange crop was completely wiped out.

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