How Different Kinds of Snowflakes Develop
It is that time of year. You know; like, where did I put the shovel? And when you find it, in the back of the garage, it is corroded and falling aprt. Or, will the snow-blower start? Yep, it might be time to run to the hardware store or make an appointment for a tune up. If you are like me, sometimes that happens after the first snow. I sheepishly admit that has happened more than once. So, hopefully, you are better prepared for winter 2017/ 2018 and have your pre-snow checklist finished. If you have handled snow for a couple of years, really anywhere in the country, you know not all snow is equal. What do I mean by that? Well, can you recall when an inch of slush was a bear, back breaker, to remove? Or, when five inches of fluffy powder was a breeze and you could have used a leafblower instead of a shovel? In Wisconsin, and most areas of the United States, you get both kinds of snow – heavy and wet versus light and fluffy. So, in this article I explain what is going on in the clouds to determine the type of snow, or snowflake, that you are going to shovel.
No Two Snowflakes Are Alike
Have you heard that before? No two snowflakes are alike. Well, one reason a snowflake is unique is that they develop in different classifications, four actually – needles, dendrites, plates and columns. What is interesting about snowflake development is how the temperature impacts the type of snowflake. Up in the clouds, most snowflake development, roughly, occurs between 5,000 and 10,000 feet above the ground. Looking at Figure 1, the temperature on the left column represents the cloud temperature, or where the snow growth is occurring in the cloud.
Why This Matters to You
The first group of snowflakes in Figure 1 is needles. Needles form when the cloud temperature is between freezing and ten below zero celsius. Because the temperature is warmer than the other groups, needles have a high water content, and because of their shape, compact to form heavy, wet snow. When snow feels like wet concrete, it is because of the relatively warmer air in the clouds forming needles. This is the type of snow we all dislike shoveling.
Now, if the cloud temperature is colder, fluffier snowflakes develop with lower water content. Dendrites are the snowflakes we made as children cutting out folded pieces of paper. Dendrites have a range though. When they develop with temperatures around twelve below zero celsius, they can still have a higher water content. That makes shoveling more difficult because of the weight or snow sticking to the inside of your snowblower. However, if the cloud temperature is closer to twenty below zero, the dendrites have less water and shoveling is much easier.
When you get to plates and columns, we are talking about cloud temperatures in arctic airmasses – minus thirty to minus forty celsius. Snow from these temperatures can come from Alberta clippers, polar airmasses moving over the Great Lakes or over the Rocky Mountains. Plates and columns are easy to shovel. This is the type of snowflake you can use a leafblower to remove.
Pay Attention to the Forecast
Predicting the cloud temperature is difficult and most meteorologists don’t discuss it on television or radio. You can be in the ballpark with cloud temperatures, but still make a bad snowfall forecast because you were off by two degrees and plates formed instead of dendrites. That changes the liquid to snow ratio and can bust a forecast. For instance, plates usually convert 7:1 versus dendrites that can convert as high as 30:1. As you can see from those ratios, that type of error can mean a snow forecast can change by an order of two, three or four. Oops.
For you on the ground trying to gauge the type of snow, just remember, the closer the temperature is to freezing, the more likely the snow is heavy and wet. When temperautres are in the low twenties or colder, fluffy snow is more likely because the cloud temperatures are between minus ten and minus 40 celsius. Feel free to learn more about snow safety and winter weather awareness through this Weather Ready Nation link and have a safe and enjoyable winter.