How is a Blizzard Defined?

Contrary to popular belief, it is the wind and not the amount of snow that differentiates a blizzard from a snow storm. This is according to the National Weather Service, who’s definition for snow storm classifies a blizzard as a storm that has strong enough winds to blow snow resulting in low visibility. To be classified as a blizzard, a snow storm must feature winds as high as 35 mph that cuts down visibility to at most .25 miles.

While cold and a large snowfall are major features of many blizzards, they are not necessary for the classification. The strongest blizzard can sometimes last for days, especially if there is an excessive amount of snow.

To be classified as a “severe” blizzard, there are certain benchmarks that it must meet. The winds must get up over 45 mph and temperatures have to dip below 10 degrees fahrenheit. In some places, such as Antarctica, blizzards have been known to feature winds as high as 99 mph.

A ground blizzard is a completely different kind of storm. While it was played for comedy in the famous Peanuts cartoon, it is absolutely true that snow can come up from the ground. A ground blizzard occurs when there is no precipitation but high winds pick up loose snow and blow it around, causing low visibility.

According to the Oxford English Dictionary, the word “blizzard” most likely has an onomatopoeic origin. Words like blister, blast and blow all relate closely to the word blizzard. It lists the first use of the word in 1829. At the time, that first use described a blizzard as a violent blow. It wasn’t until 1859 that the word made its way into the dictionary and by the 1880s it had become a common term in the United States.

While we all know that blizzards are caused by wintery conditions, there is a specific cause. Most often, blizzards are caused by warm southern air interacting with cold northern air. For instance, the Pacific Ocean sends cold and moist air to the east, where it meets warm air from the Gulf of Mexico. If any of this air dips south, then a blizzard will start to form. This is why there is so much snow in the Rockies, since that is often where the two will clash.

Another cause of blizzards in the United States is when a cold front over the Hudson Bay area in Canada shifts to the great lakes region and New England. This air can clash with the air from the Gulf of Mexico, which will cause blizzard conditions and high snowfall.

The Rocky Mountains can be a source of low pressure systems. These systems can move onto the flat land of the Great Plans and collide with the warm air there. There are fewer obstructions on the plains, so the wind can reach incredible speeds. Not only that, but the collision can cause massive thunderstorms to the south and heavy snowfall to the north. Without the obstructions to block the wind, it can reach extreme low visibility very quickly. A whiteout is when there is literally no visibility at all. People have been known to get lost on their property since they cannot see what is in front of their faces, including their own homes if they are more than 10 ft away. In these conditions, driving is incredibly dangerous and motorists need to pull over and wait until visibility is safe again.

This entry was posted in Snow Removal. Bookmark the permalink.