Weather 101: Snow-Liquid Ratios. How Surface Temperatures Play A Role!

Weather 101

Snow-Liquid Ratio. Is The Standard "10-Inches Of Snow Equals 1-Inch Of Rain" Snow Ratio Accurate?

It is a topic everyone wonders about when a snowstorm threatens Northwest Arkansas and the River Valley, snow-liquid ratios.

What Is A Snow-Liquid Ratio?

A snow-liquid ratio (or snow ratio) is a measurement of how many inches of snow equals 1-inch of rainfall.

You probably heard about the 10:1 ratio rule, meaning 10-inches of snow equals 1.00″ of rain. While this is considered the “rule of thumb” for snow-liquid ratios, it is not always accurate (especially with extremely cold temperatures).

Snowfall in Greenwood, AR on February 15, 2021. Image: Zachary Hall

Low Snow Ratios = Heavy, Wet Snow

If you have temperatures near or just above freezing, you will likely see a heavy wet snow. This means your snow ratio is lower than 10:1, probably closer to 7:1 or 8:1. So, 7 or 8-inches of snow would equal 1-inch of rainfall.

This type of snow has a higher water content, adding more weight to it. Low ratio snowfalls can cause big problems for power companies. The heavy weight of the snow can make it easier for tree branches and power lines to come down, knocking out power for many.

Anyone who has a heart condition needs to be very cautious when shoveling this kind of snow. Shoveling too fast can lead to medical problems and even emergencies, including heart attacks.

However, the heavy, wet snow is the ideal for snowball fights and snowman building as the snow sticks together.

Kids creating a giant snowball during the 2014 Super Bowl Sunday Snowstorm. Image: Sara Ford

High Snow Ratios = Light, Fluffy Snow

When temperatures fall well below freezing, we can get snow ratios far above the standard 10:1 rule of thumb. Around 10°F, we may see a “dry snow” that can produce 25-inches of snowfall with 1-inch of rainfall. Sometimes, you can go even higher to 30:1 or more for ratios.

This “light, fluffy” snow is extremely easy to move around. In fact, you can often clear your vehicle and driveway off by using a broom. Unfortunately, this snowfall is not the best for snowballs or snowman making.

Frozen Bob Kidd Lake on February 18, 2021. Image: Joe Young

Not Just Surface Temperatures!

While surface temperatures play a big role in snow-liquid ratios, they are not the only factor you need to consider. Some examples include:

  • the depth of a relatively warm layer of air from the surface into the snow-producing part of the cloud. The closer to freezing, the lower the snow ratio will be.
  • The amount of ice in the snow-producing part of the cloud. It is possible to have liquid water with a temperature below 32°F (known as “supercooled” water). The more supercooled water you have in the cloud, the lower the ratio. However, if you have a higher amount of ice crystals, your snow ratios will be higher.
  • If it’s really windy, snowflakes can fracture and lead to lower snow ratios.
Snowy sunset from February 18, 2021. Image: Tim Hudson

How Are Snow Ratios Determined?

The National Weather Service determines the snow-liquid ratio by taking the snow that falls into their rain gauge and melting it down.

Next, they pour it into a standard rain gauge to get the liquid equivalent. After a little bit of math, they get the final snow-liquid ratio for the snowstorm.

An 8-inch National Weather Service rain gauge. Image: NWS

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