Wet Snow vs. Dry Snow… Does It Make a Difference??
Well yes actually! When we (your wonderful weather people) are forecasting snow, one of the first things we look at is something called the snow ratio. A snow ratio, simply, is the amount of water you get after melting snow. The average snow ratio is 10:1, so if you take 10 inches of snow and melt it, you get 1 inch of water. That is typical. But, we often see snow ratios lower (around 5:1) or much higher (20:1). This will affect how many inches you see in your backyard! Let's explain this further…
First, let's start with a day in November (like Friday 11/5). During this time of year, temperatures in general are getting colder. Most have seen frost and many spots have had their first deep freeze, however, the ground is still quite warm and so is the air. We tend to see our first snowfall this time of year. It never stays around very long, because it's just not cold enough yet. Now, because the air is still a bit warm, the snow will partially melt before it hits the ground. This causes the snowflakes to appear very large (fat flakes). The snow ratio is low for this type of snow… around 5:1. So, for every inch of water that falls-we get 5 inches of snow. If the ground is frozen at the time, then you get that heavy, wet snow that makes great snowmen and snowballs… but is a major pain to shovel. If the ground is not frozen and temperatures at the surface are above freezing, then most of the snow will melt on contact.
Dry snow or fluffy snow falls when all of the layers of the atmosphere are below freezing-as well as the surface. Because the air is cold, the snow does not melt as it falls, so the flakes stay small. The snow ratio for this kind of snow is more like 20:1 or 30:1. This kind of snow can be dangerous because you don't need a huge storm to end up with a ton of snow, you only need a little. This is also the snow that blows around a lot and doesn't make for great snow creations. But it's quite easy to shovel (unless there are about 20 inches!).
So, why do you need to know all of this? Well, more than likely I'll never talk about snow ratios on the air. But I will talk about temperatures. If there is a weak system coming through your area and I'm talking about a half inch of liquid and temperatures in the 30's, then you know a few things. One, we will get somewhere around 2-3 inches of snow (because the ratio will be lower than 10:1). And two, the snow will be heavy and wet. If I'm talking about temperatures in the 20's and teens then stay tuned for a snow map, because there is a good chance we will see some accumulations! If it's cold enough, we could see somewhere around 10-20 inches (because ratios will be higher than 10:1)! Plus the snow will be light and fluffy.
Now, don't worry if this seems confusing. Just remember that a small-looking storm in the dead of winter may bring more of that white, fluffy stuff than you think!