Warm air can also rise to form clouds and blizzard snows as it flows up a mountainside.A powerful winter storm system will bring white out blizzard conditions and life-threatening cold temperatures as we head into the Christmas weekend. When warm air and cold air are brought together, a front is formed and snow can form. Winds pull cold air toward the equator from the poles and bring warmer, moist air toward the poles from the equator. There are two ways that moist air might rise over cold air. Moist air needs to rise over very cold air, making clouds and snow. In fact, very cold air does not make very much snow.ģ. However, cold air is not able to hold much water vapor. This is how lake effect snowstorms and nor’easters pick up so much moisture. As wind moves air over the water, some water evaporates from the surface, putting vapor into the air. Air blowing across a body of water, such as a large lake or the ocean, is an excellent source of water vapor. Moisture in the air is called water vapor. Moisture is needed to form clouds and precipitation. If the air near ground level is too warm, the snow will melt on its way down, changing to rain or freezing rain.Ģ. Cold air (below freezing) is needed to make snow.įor snow to fall to the ground, the temperature must be cold both up in the clouds where snowflakes form and down at ground level. Three things are needed to make a large snowstorm or blizzard:ġ. Blizzards can occur all over the world, even in the tropics where it is cold on high altitude mountaintops. In the United States, blizzards are common in the upper Midwest and the Great Plains but occur in most areas of the country except for the Gulf Coast and the California coast. Many times cold temperatures that can cause frostbite or hypothermia are part of a blizzard and can last for days after the storm has ended. Roads can be partially or fully blocked by snowdrifts – piles of snow formed by the wind. Travel becomes dangerous when the blowing snow causes whiteout conditions and sky and ground look white. The storm produces ample snow while strong winds develop because of a difference in pressure between the low pressure of the storm and the high pressure beyond the storm.Ĭonditions during a blizzard can be severe. Instead, snow that had fallen before the blizzard is blown around or drifts in a way to create these conditions.īlizzard conditions usually build up on the northwest side of a powerful storm system.

Some blizzards, called ground blizzards, have no falling snow. The National Weather Service defines a blizzard as a storm with large amounts of snow or blowing snow, winds greater than 35 mph (56 kph), and visibility of less than ¼ mile (0.4 km) for at least three hours. That’s what you can expect from a blizzard. The wind and the snow may cause a power outage and collapse roofs. Imagine snow so deep that second graders can’t see over the top of it. Snow whirling around in wind blowing faster than highway speed limits makes the whole world look white. NOAA National Weather Service images by Ben Jacquot Blowing snow during a blizzard reduces visibility.

White out blizzard conditions