Do you get excited when you hear snow is headed our way? Will there be a snow day? Will we get enough snow to make a snowman or have a snowball fight?
When snow is in the weather forecast, it gets our attention, and for good reason. It can make driving difficult, and it adds to our household chores, in the form of shoveling our sidewalks and driveways. But when is a snowstorm not just an ordinary snowstorm and something more?
Snowstorm isn't actually a scientific term. Any storm system that produces snow could be called a snowstorm. When we think of serious snowstorms, we think of blizzards.
Blizzard is a technical term with certain criteria. For a snowstorm to be a blizzard, there must be sustained winds of 35 mph with snow and blowing snow reducing visibility to less than a quarter mile for three hours or more.
One interesting note about blizzards: It doesn’t have to be snowing to experience a blizzard. That's right. Previously fallen snow that is blowing around because of high winds can create a blizzard if all the criteria for a blizzard are met. Blizzards that occur when snow is not falling are sometimes called ground blizzards.
Ground blizzards usually happen when an Arctic cold front moves through an area, causing temperatures to drop and winds to gust at speeds of 50 mph to 60 mph. When these Arctic fronts move through after a recent snowfall, the winds can create whiteout conditions.
More precise terms exist for other kinds of snow-producing weather systems as well. For example, snow squalls are brief but intense snow showers that occur with strong winds. Snow can accumulate quickly during snow squalls. Snow showers are brief periods of snow falling at varying intensities. Snow flurries occur when light snow falls for short periods.
Blowing snow, which is wind-driven snow that reduces visibility, is similar to a blizzard, but without the intensity. Like with a blizzard, blowing snow does not always occur while snow is falling.
Winter precipitation can be difficult to predict and define. In addition to snow, we often experience freezing rain and sleet. Sometimes sleet or freezing rain can mix with snow when temperatures are close to 32 degrees Fahrenheit.
Sleet and freezing rain both occur when rain falls high above ground and passes through a layer of freezing air closer to Earth's surface. The difference between the two has to do with how thick of a layer of freezing air the rain passes through.
Sleet is basically frozen raindrops that develop when rain passes through a thick layer of freezing air at the Earth's surface. Freezing rain occurs when rain passes through a very thin layer of freezing air and the raindrops don't have time to freeze before reaching the ground. These raindrops then freeze on contact with surfaces, creating a coating of ice.
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