"Nature Guide Journal"

14 December 2000

For some people—children especially—December marks the beginning of close sky-watching in anticipation of snow. Although an individual's appreciation for snow may vary according to whether or not they play in it or shovel it, snow is undeniably remarkable.

"Snow" is a form of solid water that develops in clouds of certain temperatures. Because of their high altitudes, most clouds are cold enough for their water droplets to be frozen or supercooled (below freezing, but not frozen). Between 0º and -5º C, ice crystals that form can readily stick together and build complex shapes as they move through the cloud.

Yes, it can be "too cold to snow." Very cold clouds hold less water vapor and their ultra-hard ice crystals are not sticky enough to cling together to form flakes. Even within the right temperature range, there's a lot of variation in the shapes of the snowflakes that evolve.

The classic, six-branched snowflake is probably the most familiar of the seven to ten classified snowflake shapes. The hexagonal plate (with simple, straight sides) and divided hexagon (with internal divisions) are also widely-recognized snowflake patterns. Snow crystals and flakes shaped like needles, sheaths, capped columns, and irregular shapes are less familiar—possibly because they're less decorative.

The old saw that "no two snowflakes are alike" is not true: researchers have found several sets of naturally formed identical snowflakes.

The ultimate size and shape of snow crystals and flakes depend on the cloud's temperature, the amount of water available, and the size of the water droplets. In drier, colder air, the developing ice crystals tend to stay small and separate; in humid air the crystals are more likely to collect and form larger, more complex shapes. The air on the Oregon Coast is frequently humid enough to cause enormous snowflakes that grow far beyond their original delicate structures.

While circulating through the clouds, ice crystals sometimes clump into irregular masses (called soft hail or graupel) instead of flakes.

Most snow melts to become rain as the falling flakes drop to lower elevations. "Sleet" is rain (or melted snow) that freezes as it falls to the ground; "freezing rain" is rain that freezes upon contact with the ground or other surfaces. "Hail" is an ice particle that is tossed about in the cloud among frozen and liquid water, repeatedly collecting liquid water then freezing. The concentric layers of ice make the resultant hail stone look like an old-fashioned jaw-breaker.

Our temperate climate makes for a rare, short-lived existence for these beautiful and infinitely diverse solid-water constructions. With luck, we'll receive enough snow to delight those who watch and play in it—though we rarely receive enough to vex those who shovel it!  

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Wavecrest Discoveries can craft your personal discovery of this delightful part of our world by customizing one of our distinctive guided excursions.   Our walks, tours, and special activities are wonderful ways to explore this fascinating region—and are the perfect entertainment for guests.