Wilderness Underfoot: The recipe for snow

StoryImage( ‘/Images/Story//Auto-img-113338541711410.jpg’, ”, ‘Snow is crystallized water – The basic snowflake structure is hexagonal with a variety of shapes that can form depending on temperature. At 3° to 10°F, the star-shaped “dendrites" (branches) form. Between 10° and 14°F, the flat hexagonal plates form. Between 14° and 21°F, the hexagonal columns form. Between 21° and 25°F, the spikes or needles form. When the temperature reaches 25° to 32°F, the hexagonal plates form again. The variety of shapes comes when snowflakes are blown about in layers of varying temperatures. ‘);
StoryImage( ‘/Images/Story//Auto-img-113338553511412.jpg’, ”, ‘A wealth of snow –Average snowfall here each year is between 10 inches downstate and 36 inches in the northern part of the state. Because Illinois experiences weather extremes, these ranges can vary wildly. The greatest 24-hour snowfall here was nearly 38 inches in the town of Astoria in central Illinois, back in 1900. The city of Aurora holds the record for greatest seasonal snow-fall during the winter of 1978-1979: 105 inches!’);

Nature creates snow from a speck or two of dust, some water vapor, and just the right temperatures

It is said that no two snowflakes are identical. Molecule by molecule, crystal by crystal, you would never get a perfect match. That doesn’t mean there aren’t virtually identical snowflakes, however.

Unlike sleet, snow doesn’t begin as water droplets. Instead, it comes from water vapor that turns from a gas into a solid without passing through a liquid state. Snowflakes form in clouds.

A snowflake is created when the humidity is high and temperatures fall below 32 degrees. Water vapor condenses around a tiny speck of dust, and slowly builds in size and complexity. Its final shape depends on air temperatures and other atmospheric conditions it is exposed to while it is forming.

A snowflake’s magic number is six—the number of sides of a hexagon. Any plates, columns or needles that form on the flake will be hexagonal in one way or another, due to the inherent crystalline structure of ice. Although we think of snowflakes as being symmetrical (all six sides matching), this is not always true, especially if they are blown around while forming.

Illinois lies in the path where Canada’s cold north winds swing low to meet the moisture-laden winds of the Gulf of Mexico, so our state gets a generous serving of snow each year. Water vapor from the Great Lakes also contributes to our snowfall. With such an abundance of winter snow, this is a great opportunity to take a magnifying glass outside and observe snowflakes up close for yourself.

From the Nov. 30-Dec. 6, 2005, issue

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