Now that we’re well into Winter here at the October Country Inn, we routinely check the thermometer, and look out the window to gauge the kind of snow, before we venture outside, the best way to dress, and choice of footwear for the activity we plan to undertake given the differing types and conditions left by our most recent snowfall. Although commonly said, it turns out that Eskimos do not have over one hundred words for kinds of snow. They probably have about as many words for snow as Vermonter’s do. After all, Vermonter’s have ample opportunity to contemplate the many ways that Winter’s moisture falls to the ground, and accumulates there, during the months from December through March.
Snowfall forms on dust in the air.
Basically, kinds of snow are formed when dust particles in the air act as a nucleus for condensation. Water vapor condenses on the dust, and as the droplet grows and is cooled, it freezes into an ice crystal. The crystal grows heavier as more water vapor condenses, and begins to fall. As it falls, continued condensation changes the crystal’s shape. The crystals clump together into snowflakes as they fall out of a cloud into warmer air.
Atmospheric conditions, such as the amount of supersaturation and temperature of the air, affects how snow crystals form, and what happens to them when they fall to the ground. Freshly fallen, unpacked, symmetrical six-sided snowflakes are called powder. Freshly fallen snow can also become hoarfrost when it lands on a surface whose temperature is colder than the surrounding air. Graupel is the name for snowflakes that become rounded, opaque pellets, with a texture softer and more crumbly than hail. Finally, when water vapor remains more liquid, it either freezes into balls of ice before it falls to the ground as hail, or as freezing rain that falls as liquid rain and then forms a thick coat of ice on every surface it touches.
There are many kinds.
Apart from the kinds of snow, snowfall can also occur in different ways. The intensity of snowfall is determined by visibility. Light snowfall occurs when visibility is over 1 kilometer (0.62 miles). Moderate snowfall occurs when visibility is restricted to between 0.5 and 1 kilometer. When visibility is less than 0.5 kilometer, snowfall is considered to be heavy.
A snowstorm occurs when large amounts of snow fall. Snowfall can be further described as a blizzard, when subfreezing temperatures and strong wind last more than 3 hours; a flurry, when snow falls for short durations with varying intensity; a squall, when snowfall is brief but intense; or a snowburst, when snowfall is very intense for a brief period. Then, once snow is on the ground, the snowpack can acquire many different characteristics, and formations. New snow is recently fallen and the original form of ice crystal can be recognized. When it can’t be recognized, is becomes old snow. Névé is young granular snow that partially melted, refroze, and became compacted. Névé that survives a full melt season is called firn.
Snow is no simple matter.
The further action from periods of shade or sunshine, air temperature, and surface wind can also produce differing kinds of snow formations. Corn is a type of coarse, granular wet snow typical during the Spring. Crust is a hard snow surface lying on a softer layer. Crud covers a variety of winter conditions including windblown powder leaving crust patches and ridges, or refrozen wet snow leaving a deeply rutted surface with loose chunks (also called death-cookies).
Penitents are tall, thin, closely spaced pinnacles of hardened snow ranging in height from a few inches or a few feet. Sastrugi occurs when wind erodes or deposits snow in irregular grooves and ridges. A cornice on the edge of a ridge is an overhanging accumulation of ice and wind-blown snow. A barchan is a horseshoe-shaped snowdrift with the ends pointing downwind. Snow cups are a pattern of shallow, bowl-shaped hollows that form during intense sunshine. As you can see, there’s a lot to be considered when preparing for a day of Winter fun in Vermont.