Meteorologists will often use the term “snow ratios” when talking about the differences between different snow types. Just as there are different types of snowflakes, there are certain patterns to look for when forecasting that can show how snow will form, accumulate, and eventually impact us at ground level.
A very general rule of thumb for snow ratios is 10:1. That means for every ten inches of snow that falls, there would be a one-inch liquid equivalent. If you look at a model that has a snow output, the snowfall ratio is likely 10:1.
Snowfall that has a lower ratio (ex. 5:1) will be described as heavy, wet snow that can fall when temperatures are right around freezing, like in a nor’easter. This can be tough to shovel and cause a quick slush on roads While this snow will not amount to much, it can cause big problems for drivers.
Snowfall that has a higher ratio (ex. 15:1) will be described as light, fluffy snow that falls when temperatures are in the 20s or colder. Generally, when the temperatures are colder, snow ratios will be higher. This type of snow can happen within lake-effect snow bands and while do not cause major travel concerns at lower amounts, this type of snow can pile up very quickly and help inflate snowfall totals. In some cases, the snowfall ratios can climb up near 20:1 or even 30:1.
Snowfall can be captured and then melted to calculate the ratio. Lower ratios are more common across the Northeast while higher ratios are more common within the Great Lakes.