First Snow

The wind is blowing at 30 miles an hour, and snow is flying sideways past my study window. The birds on the bird feeder are facing into the wind, and the dogs are joyously cavorting in the snow. The temperature is around 32 degrees. The snow is wet and sticky, plastered to the vertical surfaces by the wind. Six to eight inches of it will blanket everything by the time it’s done. There’s always something a little magical about the first snow of the year. Until you have to clear out the drifts anyway.

It is an old saw that Eskimos have a hundred, or a thousand, words for snow. Although they may not actually have that many, clearly, they differentiate among the various types of snow. We’re not snow aficionados, and we don’t ski or snowboard, but we recognize the differences in our snow.

There are, in fact, several types of snow-related winter precipitation seen on Owl Acres. Each kind is formed under specific conditions in the clouds, in the layers of the air below the clouds, and on the ground.

The heavy wet snow with its big flakes and tenacious clumping is formed when the air is moist relatively speaking, and the temperature on the ground hovers just above freezing (32-34 degrees F). As the snow crystals tumble through the atmosphere, their edges begin to melt, and they tend to stick together, forming big flakes. If the temperature rises a bit, the snow may turn to sleet or freezing rain.

Freezing rain occurs when the snow that formed in the clouds falls through a warmer layer of air, then a colder one before hitting the ground. When the snowflakes hit the warmer layer of air on their way down, they melt into drops of water. When these water droplets fall through the next, colder layer of air, they become super-cooled to between 28 and 32 degrees F. The super-cooling happens because these droplets formed from melting snow rather than around a core of dust. This allows the droplets to remain liquid for four or five degrees below freezing. But then they hit a cold, solid surface like the ground or a tree branch. They spread on impact an then instantly freeze into clear ice. The immediate result is a coating of clear ice on every surface.

Sleet is formed by a similar process. Snow melts as it falls through a warmer layer of air, and then it freezes when it falls through a colder layer of air. The difference here is that the droplets of water have time to refreeze before they hit the ground, bounce, and settle. When it’s sleeting, you can hear the little needles of sleet hitting the windows.

Snow pellets are similar to hail but much smaller. They form when water in the clouds freezes around the snow crystals forming little balls. Like hail, they fall to the earth intact and form a grainy kind of snow.

Depending on the temperatures in the clouds, the atmospheric layers, and the ground, we’ll see rain, sleet, freezing rain, snow pellets and/or snow., often mixed together as the temperatures change.

At the other end of the snow spectrum is the light, powdery snow that falls when the temperature on the ground is below 25 degrees F. The air tends to be drier, and the flakes are small and light. This kind of snow doesn’t stick well for snowman-building, but makes for excellent skiing and sledding.

We are happy to see the snow this winter. Not only does it bring much-needed moisture, but it also brings an insulating ground cover. A blanket of snow will keep the ground more moist. It will also insulate the ground from subfreezing temperatures. By keeping the ground a bit warmer, the frost doesn’t go as deep as it does on bare ground.   I never quite figured out how snow can be an insulator, but it is. It turns out that the insulation factor is in the air between the snow crystals. Like the air trapped in a bird’s feathers or a dog’s fur, or my winter coat for that matter, the air trapped in snow maintains a fairly constant temperature. In the case of snow, that temperature is around 32 degrees. That sounds pretty cold, but when temps drop below freezing it’s actually warmer than the ambient air.

Right now, the wind is howling outside and a blizzard is blowing. It feels good to be warm and safe inside.

Photo by Author. Alt text: The dogs are loving First Snow.  Golden Retriever Clancy and Yellow Labrador Retriever (and Seeing Eye Guide) Dave stand opposite each other mugging the camera, in a white snowscape.  Woods, the propane tank and the enclosure fence populate the background.