Meteorologists track and predict weather conditions using state-of-the-art computer analysis equipment that provides them with current information about atmospheric conditions, wind currents, temperatures, precipitation and more. The information collected is used to create different possible scenarios or models. These are used as the basis for most weather predictions.
In order to qualify as a blizzard, a winter storm must have low visibility, excessive wind gusts of more than 35 mph, temperatures less than 20 degrees and a duration of at least three hours. Since many harsh winter storms meet some but not all of these criteria, it is possible to have blizzard-like conditions even in the absence of an actual blizzard.
There's an approximate 15 percent error rate in meteorologists' weather predictions, according to the National Weather Service. This means that weather forecasts are accurate more than 85 percent of the time. However, weather predictions are less reliable when they are made days and weeks in advance than they are when they are made just before weather conditions are expected to change. For example, many winter storms are downgraded or upgraded as the day of the storm's arrival approaches. This is because weather conditions are constantly changing in unpredictable ways.