Have you ever heard a forecast for ‘wet snow’ or ‘dry snow’ and wondered what that actually means? Well, with just a little bit of mathematics (we promise it won't be daunting) let's investigate how liquid water amounts and snowfall accumulations are related!
First and foremost, snow is just ice crystals that fall from clouds when the air temperature is generally below or near 32°. However, the amount of water that is in these snowflakes and the temperature at which they form make up the snow ratio and help to determine accumulations. In other words, the snow ratio is simply how much liquid would result if you melted the snow. The average snow ratio is 10 to 1 (10 inches of snow for 1 inch of liquid water), which is usually seen with temperatures near 32° or just below. However, ratios can be as low as 5:1 with bad snow growth/warmer surface temperatures and as high as 20:1 or 30:1 with temperatures in the teens and single digits.
Now what’s up with wet snow vs. dry snow? That has to do with how dense or ‘watery’ the snowflakes are that are falling. Dry snow is the powdery and loose snowfall that is lighter and easier to shovel. This is due to the lower liquid water content within the snow, which allows for less sticking between snowflakes and relates to the higher snow ratios, like 15:1 and 20:1. On the other hand, wet snow relates to lower snow ratios, at and below 10:1, which means there is a higher liquid content within the snow. In turn, it is much denser and allows for sticking between snowflakes. Put this together, and you have snow that is harder to shovel and is very easy to form into snowballs. Finally, the dense and heavy nature of wet snow is what makes it so dangerous, as not only is it physically strenuous to shovel, but it also weighs down on tree limbs and power lines, allowing for the threat of power outages and injury.
Above: Heavy, wet snow can bring down tree limbs like in this scene from October 29, 2011