If you’ve experienced snow on more than one occasion, you likely noticed that it’s never truly the same. Some snow is sticky and wet, while some is powdery and dry. But wait, isn’t snow created from water? How can it be dry? I understand the confusion, believe me. Snow is a strange thing, never falling in the exact same way. I want to try to explain some major differences in snowfall, though. The most apparent is the difference between wet and dry snow. If you’ve tried to build a snowman with the latter, or perhaps made a too-hard snowball out of the former, this will hopefully clear up some confusion.
Snow can be wet and dense or light and powdery. Surface temperature is the primary cause for these differences. When the surface temperatures are just above freezing, snow can melt slightly, which adds more moisture. The added moisture melts crystals around the edges, allowing them to stick together and become big, heavy flakes. This creates heavy, wet snow, which sticks together easily and is perfect for building snowpeople and other structures.
In contrast, light, powdery snow contains less water. Generally, around five inches of dry snow will melt to be only half an inch of water. The same amount of wet snow will melt to be around an inch of water. Powdery snow is formed when air temperatures are very cold. Dry, cold air will produce small, powdery snowflakes that don’t stick together. These are more likely to drift in windy weather, and they are less likely to cause ice build-up.
Snow is a tricky thing, and it can be difficult to anticipate the types of activities and precautions you may need to take to prepare for a large storm. The best way to anticipate the type of snow is to keep an eye on the temperature when snow is forecasted. When temperatures hang out in the mid-30s, it is likely to be heavy and wet; anything under 32 and the snow will be relatively harmless powder.
This is a snow appreciation site, which means we want to cover as much information about this weather phenomenon as we can. Sure, snow looks magical, and it has the power to transform a bleak January day into a sparkling winter wonderland. But snow itself is fascinating. Its formation seems nearly impossible; conditions have to be just right to produce the necessary crystals. Here, I’m going to lay out just how crazy snow formation is—hopefully, it’ll spark a deeper appreciation for it.
So, what exactly is snow? It’s solid precipitation that occurs in the form of a variety of small ice crystals. Snow forms when tiny crystals in clouds stick together to become snowflakes. If enough crystals stick together, they become heavy enough to fall to the ground. Isn’t that a neat image? Small particles in the clouds above us sticking together and eventually dropping out of the sky. I think that’s pretty neat.
Snow is formed when temperatures are low and there is enough moisture in the atmosphere to form tiny ice crystals. Precipitation falls as snow when the air is below 36 degrees Fahrenheit (around 2 degrees Celsius). You might be raising your eyebrows right now. Yes, you read that right—it doesn’t have to be freezing or below freezing for snow to form. In fact, the heaviest snowfalls often happen when the air temperature is between 32 and 36 degrees Fahrenheit. If, however, the temperature is warmer than 36 degrees, the snowflake will melt as it falls, landing as sleet or rain.
Snow density depends on the moisture of the air and the number of crystals clumped together. There are endless types of snowflakes (you’ve likely heard that each is unique; while it’s impossible to prove this, it could be true), and each is impacted by the formation temperature, precipitation temperature, wind, and path to the ground. Snow can dramatically alter a landscape in a matter of hours, and—when considered alongside this crazy formation process—it is perhaps one of the most interesting weather phenomena out there.
Looking back at 2017 and the early snowfall schedules, the story has undoubtedly been a country divided—with the Eastern half of the country including the Great Lakes and the entire East Coast experiencing heavy snowfall and sub-zero temperatures. Erie, PA already known for big annual snowfall totals broke a two-day record for snow this year. The Western U.S., by contrast, has been relatively mild and relatively dry during the early winter season.
It’s kind of the worst of all possible scenarios. More than just skiing and alpine recreation, much of the Western U.S. depends on snow and the resulting snowpack to keep and protect their water supply. The dry conditions have extended even into California which is experiencing devastating wildfires followed by horrific mudslides.
While there are definitely recreation advantages to heavy snow and sub-zero temperatures in the East—from skiing to ice fishing to other winter sports—there also tens of millions of people who are just trying to get to work each day without feeling like they’re risking their lives. Indeed, dozens and dozens of people have already lost their lives to the wintry conditions.
Last year, in 2016, at least the western side of the Rocky Mountains saw a good amount of snowfall. Now, everywhere seems warm and dry. Much of Colorado’s snowpack is once again approaching a dangerously low level.
This type of uncertainty and regional disparities also seem to be happening with increasing frequency. Long-term climate forecasts suggest that global warming is likely to have a mixed effect on winter-like conditions overall, with a high-degree of variability and the potential for monster winter storms also on the rise.