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Posted at 11:00 AM ET, 12/10/2008

The Science and Wonder of Snowflakes

Wx and the City

* Mild Showers, Then Cold Rain: Full Forecast | Weather Wall *

With the D.C. area's first dusting of snow this past weekend and the slight possibility of more flakes this week, I got to thinking: What's so great about the white stuff?

Is it the magical twinkling of white crystals blanketing the ground? The opportunity for winter sports and outdoor play? The justification of cold temperatures, leafless trees and gray skies of winter, and the excuse to stay inside? The fact that no footstep is left untraced? Or the opportunity to see snowflakes, a manifestation of art and symmetry in nature?

I choose all of the above, with an emphasis on snowflakes. The science of snowflakes is one of the most amazing aspects about snowfall.

Keep reading for more on the science and wonder of snowflakes...

In order for snowflakes to form, atmospheric conditions must be just right; precipitation in a winter storm can change quickly and is very affected by temperature, humidity and wind. A snowflake is formed when a supercooled water droplet freezes onto a dust particle or other cloud nucleus, becoming an ice crystal. More and more ice crystals join on, forming a snowflake. Eventually, the aggregation is too heavy and falls several thousand feet to the ground. If the snowflake is fortunate enough to remain at or below freezing all the way to Earth's surface, it remains a snowflake (rather than turning into another type of wintry precipitation such as sleet).

Different temperatures and humidity levels along a snowflake's journey to the ground influence the shape it takes. Drier, colder snowflakes will often form feather-like dendrites (my favorite), whereas warmer flakes with more moisture content will form other plates or columns. Many snowflakes take on a hexagonal shape due to the lattice structure formed when water molecules join together. Furthermore, snowflakes that coalesce can form bigger, fluffier or asymmetrical shapes.

The first person to successfully photograph snowflakes was Wilson "Snowflake" Bentley, a farmer from Vermont who gained a fascination with the white stuff in the late 1800s. You can check out his photo gallery here. Other images of snowflakes worth looking at are the USDA Electron Microscopy Unit Snow Page and

The best part about all of this? You can easily learn to identify snowflakes yourself by catching them on a (cold) piece of black construction paper, checking them out with a magnifying glass, and finding their match using this printer-friendly guide.

Let's cross our fingers for some more snowflakes soon.

By  |  11:00 AM ET, 12/10/2008

Categories:  Science, Science, Science, Science

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