Blizzards! What causes them?

Firstly You Need Cold Air. The air has to be below freezing to make the snow. It has to be cold in the sky where the snowflakes form and on the ground for snow to fall. Because if the air at ground level is too warm, the snow will melt on its way down and turn into rain.

Secondly you need moisture. Moisture is needed to form clouds and precipitation. Moisture in the air is called water vapour. You get it from air blowing across a large body of water such as a lake of the sea. As the wind moves across the water, some water evaporates from the surface and puts vapour in the air. However cold air isn’t that good at holding moisture, so very cold air doesn’t make that much snow.

Thirdly you need warm rising air. This is needed to form clouds and cause precipitation. The warm air has to rise over the cold air. This can occur two ways – one way is winds pull cold air towards the equator from the poles, and they bring warm air towards the poles from the equator. When cold and warm air masses meet, they cause a front and precipitation occurs. The other way is warm air can rise to form clouds and blizzard snows as it flows up a mountainside.