The science of snow ratios
No two winter storms are alike, making them a challenge to forecast. Similarly, no two snowflakes are the same, varying in size, shape and texture.
One key factor in determining the texture of snow is the snow-to-liquid ratio., meaning how much liquid water is present in a set quantity of snowfall. Low snow ratios tend to yield heavy, wet snow, while higher snow ratios produce lighter, more powdery snow. On Wednesday, Feb. 12, several inches of fluffy, powdery snow fell across Northwest Missouri and Northeast Kansas, indicating a higher snow to liquid ratio.
A common example that produces drier, powdery snow is a 20:1 ratio, meaning it takes 20 inches of snow to produce 1 inch of water. Snow ratios of 15:1 or higher typically result in the type of snow we saw this past week. When strong winds accompany dry snow, it tends to blow around very easily, quickly resulting in low visibility. At times, dry, powdery snow can even cause blizzard conditions just from being picked up off the ground when winds are strong and steady.
When snow is wetter and slushier, it typically has a snow ratio of 10:1 or lower. In this case, 10 inches of snow equates to 1 inch of water. This type of snow is ideal for winter activities like snowball fights and making snowmen. On the flip side, lower snow ratios also means the snow has more weight. Sometimes called “heart attack snow,” heavy wet snowfall can be harder to shovel, and create more strain on the body for those doing their best to clean it up. Trees, powerlines and other structures are at a greater risk of breaking when snow is heavy and wet, especially if it takes place when there is foliage present on deciduous trees in spring and fall.
The primary factor that influences snow ratios is the temperature in the lower and middle atmosphere. In general, colder air temperatures yield higher snow ratios, efficiently squeezing the most moisture out of the atmosphere. When air temperatures are closer to freezing, snow ratios tend to be lower with more water present in each flake.
While colder air generally yields higher snow ratios, there are many caveats to this. If a column of cold air is not deep enough, or a warmer layer is present, snow ratios can drop even if surface temperatures are bitterly cold. Wind can also influence snow ratios, sometimes breaking and shredding snowflakes, leading to a lower snow to liquid ratio.
