The National Weather Service defines snowstorms or blizzards as storms in winter with sustained or gusting winds of 35 miles per hour, producing blowing or drifting snow that is accompanied by reduced visibility up to one-quarter mile or less for over three hours. They are often accompanied by extremely cold temperatures. The amount of snow has little to do with a storm to qualify as a snowstorm, but rather the intensity of the winds and length of time matter.
The Hard Facts About Snowstorms
Snowstorms are accompanied by fierce winds, freezing temperatures, reduced visibility, and snowdrifts. The aftermath of a blizzard can be as dangerous as the storm itself.
The aftermath of a blizzard could be as dangerous as the storm itself
Blizzards can occur after a snowfall when high winds cause whiteouts (fallen snow blowing around) and snowdrifts (huge mountains of snow), which decrease visibility. They have been known to come suddenly and while it is possible to be warned in advance, it is not always possible to be entirely prepared for the intensity of the blizzard. Clearing the roads is not possible until after the blizzard has passed and even then it takes a long time due to the intensity of the buildup. The aftermath of a blizzard could be as dangerous as the storm itself as people trapped inside vehicles, unheated buildings, or outdoors take longer to be found or brought to warmth and safety.
One of the primary concerns is the winter weather's ability to knock out heat, power and communications services to your home or office, sometimes for days at a time. Heavy snowfall and extreme cold can immobilize an entire region.
Visibility is drastically reduced, in some instances, to as little as 3 meters or what is called zero visibility. In a ground blizzard, though no new snow is falling, the snow already on the ground is whipped up and around by the winds.
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How do blizzards form
Many blizzards stem from Nor'easters, which are storms travelling up the east coast of America. Moisture gathers from the Atlantic and dumps large accumulation of snow from Delaware to Maine. Rochester, NewYork is said to be the largest city with the most snow in the U.S., accumulating an average of 94 inches of snow every year.
For snow to fall on the ground, the temperature must be cold, both up in the clouds where snowflakes form and down at the ground level. Moisture in the air or water vapor is required to form clouds and precipitation. Air blowing across a large lake or an ocean is an excellent source of moisture. As the wind moves air over the water, some water evaporates from the surface putting vapor in the air. This is how Lake effect snowstorms and Nor'easters pick up so much moisture. Warm rising air is needed to form the clouds. For a blizzard to form, it must rise over cold air. The winds pull cold air from the poles toward the equator and bring warm air toward poles from the equator. When warm and cold air are brought together, a front is formed and precipitation occurs. Warm air can also rise up to form clouds, and the blizzard snows as it flows up a mountain side.
Types of icy precipitation
- Snowflakes: These are made of ice crystals, each containing as many as 200 of them. They form in clouds where the temperature is below the freezing point. The water droplets condense around tiny bits of dirt that have been carried up into the atmosphere by the wind. As the snow crystals grow, they become heavier and fall towards the earth.
- Graupel: Snowflakes that have been encrusted with ice. This happens when flakes pass through a chilly cloud on their way down, and water droplets freeze on them.
- Ice pellets: These are the frozen raindrops that are quite small in size, and do not have a crystalline shape.
- Hail: A frozen raindrop or a graupel that is kept from falling to the ground by the upward flowing air of a thunderstorm.
Technical terms used in weather reports, advisories and warnings of blizzards and freezes
- Freezing rain: The rain that freezes when it hits the ground, creating a coating of ice on roads, walkways, trees and power lines.
- Sleet: The rain that turns into ice pellets before reaching the ground. Sleet causes moisture of the roads to freeze, making them slippery.
When a blizzard is in the forecast, you may receive the message as a "Winter Storm Watch". You could also receive a "Winter Storm Warning" which means a storm is already on the way or taking place, and you got to get prepared. You could lose electricity, so stock up on non-perishable foods, blankets, flashlights, extra batteries and candles beforehand.