Snow Science and Winter Folklore
Winter is arriving in the Blue Ridge! We got about four inches of snow last Friday, and though it melted quickly we know more will be on the way soon. It’s about time to break out the jackets and sleds, make sure enough firewood is stacked for the season, and stock up on winter essentials like soups and hot chocolate.
BRDC’s historic schoolhoused dusted with snow.
Watching the snow fall is a beautiful sight to behold, but for the curious, snow can spark a lot of questions. How does simple ice form such intricate shapes? And why do snowflakes look the way they do? Read on and find out.
Types of winter weather
In the Blue Ridge mountains, we see several kinds of snow precipitation. Often, the ground temperature is too warm to accumulate more than a dusting. Light snows are called flurries, and they are usually short events. A snowstorm may last for a few hours and result in significant accumulation. Blizzards are heavy winter storms defined by winds greater than 35 mph, and snow precipitation reducing visibility to less than ¼ mile for three hours.
Snow forms whenever the temperature in a cloud is below freezing. But for those snowflakes to make it to the ground, the temperature must stay below 32F for its entire trip through the atmosphere. In reality, the atmosphere is a large and chaotic place, and different conditions can create different types of winter weather.
If precipitation passes through a thin layer of warmer-than-freezing air, snowflakes partially melt and refreeze into sleet. Sleet is granular frozen precipitation that bounces on impact; it's often somewhat fluffy since the snowflakes may not thaw entirely.
If the layer of warm air is thicker, allowing snowflakes to melt completely, the precipitation may become freezing rain. The water does not have time to crystallize into ice, remaining a liquid even as it is cooled by sub-freezing air near the surface. Then, upon impact with surfaces at or below 32F, the rain suddenly solidifies into a thin layer of ice.
Snowflake formation
To make snow, a cloud needs high humidity and low temperatures. Minute changes in these variables affect the shape of snowflakes. For example, higher humidity can make larger snowflakes while warmer temperatures tend to form more complex shapes.
Snowflakes get their classic six-fold symmetry thanks to the shape of water molecules. If you imagine a water molecule (H₂O) as the shape of Mikey Mouse’s head, you can see that water will neatly fit into a hexagon, with a hydrogen atom of one water molecule facing the oxygen of the next.
Before a snowflake can form, the water vapor in the cloud needs something to bind to and freeze. Particles of dust, smoke, or large polar molecules like sulfates can all function as “condensation nuclei”, around which a single snowflake will grow. In seconds, a hexagon of ice will form around this nucleus. As the prism drifts along air currents throughout the cloud, it experiences small changes in humidity and temperature, all the while collecting more water molecules on its six facets.
The way water molecules attach to the snowflake depends on minute changes in temperature and humidity in the cloud. Since all six faces experience the same conditions simultaneously, ice crystals will form very similarly on each. This is also why snowflakes are so unique—no two flakes will experience the exact same chaotic fluctuations in temperature and humidity.
Wintertime folklore
Life for the early settlers of the Blue Ridge Mountains wasn’t easy. The rolling mountains and deep valleys of the Blue Ridge made roads very difficult to construct and maintain, and the high elevation means winters can be long and hard. The Appalachian folk depended on what they could grow, hunt, and forage themselves, and trade with their neighbors for whatever else they needed. Homesteaders had to ensure they had enough food preserved, wood chopped, and clothes made to last through the winter.
This dependence on the land and their communities lead to plenty of folklore, especially ways to predict how hard the coming winter would be. While a few of these traditions are somewhat logical, many seem superstitious today. That said, generations of homesteaders lived through countless winters in these mountains so there may be something to their advice.
Bean jar
During the month of August, place one small bean in a jar for every hazy morning, and one large bean for each foggy day. In the winter, remove a small bean for each flurry and a large bean for each heavy snow. Homesteaders would do this to predict the harshness of the winter: the more full the jar is at the end of the month, the worse winter to expect. Farmers would also use this estimation for the last frost of spring. After removing the last bean, they could prepare to sow spring seeds.
Wooly worms
The caterpillars of the Isabella Tiger moth, Pyrrharctia isabella, mature in late summer and begin to wander in late September and early October. During their wandering stage, they leave the plants they have been feeding on all fall and seek a safe location to pupate over winter. They are about three inches long, have thirteen segments, and are covered in a dense coat of spines—black at the head and tail ends, and orange or brown through the middle. There is a tradition to catch these caterpillars and count the number of black and orange bands. Each segment stands in for a week of winter, with lighter-colored bands representing mild weather. More more black bands are said to forecast a harsher winter to come.
Persimmon seed
Cut into a seed from the first persimmon to fall from its tree and see the shape of the cotyledon, the opaque white tissue in the middle of the seed. If it comes to a pair of points, this is a fork. Seeing a fork foretells a mild winter, with good eating. If the seed casing is round, this is considered a spoon, and you may have to scoop your way through snow this winter. If it is thin and sharp like a knife, beware! This will be a bitingly cold winter that cuts like a knife.
Animal behavior
Watch the animals as they prepare for winter. Beware if monarchs and geese and other waterfowl migrate early. Watch for how high the wasps nest, as they stay well above where the snow comes to rest. If the forest produces more mast (berries and nuts) than normal, nature is preparing the animals for a long winter. Notice if the woodpeckers share a tree, the squirrels clear the ground of acorns, if ants march swiftly in straight lines rather than meander, or mice try harder than normal to get into your house. Feel how thick the hair is on the fall hunt and on the nape of the cows’ necks, and beware if pigs gather sticks.
Science and folklore have more in common than may appear at first glance—after all, they’re just two ways of understanding the world around us. Why not make observations and conduct experiments of your own this winter, and see what holds true for you?
