Waiting for Frosty

We all seem to know when we want it, there’s folks who prefer having snow when "there’s no place to go." We even wrote a song to that effect "let it snow, let it snow, let it snow." Ranking above that concern, is the desire for a white Christmas, we wrote a song to that effect too. The kids, of course, hope for snow anytime, but it’s even better when there’s school closings. So it seems everyone hopes for it at one time or another, but what exactly is that white stuff we write ditties about?

We were told as children that every snowflake was different, and each flake was an example of perfect symmetry. But is this really so? First, let’s look at why we have snow in the first place.

Aristotle believed that when a cloud freezes, there is snow. Okay, how then, would you explain hail and sleet? Clearly there has to be more to it than that.

Ice crystals form in the upper atmosphere when water vapor freezes around dust particles such as mineral dust, sea salt and industrial dust particles. The particles are less than a tenth of a millimeter in diameter and form the nucleus for the ice crystals to attach and grow.

These ice crystals collect more and more water vapor, growing in a widening circle pattern. The ultimate size of the snowflake depends on temperature, humidity, wind and barometric pressure. Generally, the higher temperatures and humidity levels grow the largest and most elaborate snowflakes.

As the crystals begin to fall, they bump onto each other, breaking pieces off that in turn begin to grow. As the temperature increases, some of the crystals melt slightly and adhere to other groups of crystals and a snowflake is born. An individual snowflake may contain thousands of crystals.

There is a classification system for snowflakes which recognizes seven basic types: plate crystal, stellar crystal, column, needle, spatial dendrite, capped column, and irregular. Our "classic" snowflake, is the stellar type, shaped like artists conceptions of stars. They are less common because they have to fall undisturbed.

Complete snowflakes can only make it to the ground as such if the temperature consistently stays below freezing. Nearly all snowflakes have six sides, but what shape they tend to take depends on the temperature. If the temperature in which they have formed and through which they have fallen is above 27F, the flakes tend to be flat and hexagonal. From 23 to 27 degrees, flakes tend to be needle shaped. Between 23 and 18 degrees, they will usually be hollow and columnar. Below 18 degrees, snowflakes tend to be hexagonal, columnar and the lacy traditional snowflakes.

The popular belief that no two snowflakes are alike is probably true. For two snowflakes to be exactly alike, they would have to form in exactly the same way and both would have to fall in an identical manner.

As "pure as the driven snow" however, is a misnomer. As mentioned earlier, snow crystals form around a nucleus of particles, and they also pick up other trace amounts of sulfates, potassium, calcium and nitrates from the particles and the atmospheric gasses, and industrial pollutants.

If you would like to try observing snowflakes, all you will need is a magnifying glass, and a piece of dark material stretched over cardboard. Pick a snowfall that is around 25 degrees F, and little or no wind. Let the fabric become cold before you start gathering snowflakes and you will see more detail in the flakes. Perhaps you will even discover two identical snowflakes!