When we talk about snow quality, such as “light and fluffy” or “heavy and wet”, we are talking about the Snow-to-Liquid Ratio, known as SLR.
To calculate the snow-to-liquid ratio, divide the amount of snow by the depth of water you would measure if you melted the snow into liquid.
The higher the snow-to-liquid ratio, the lighter the snow quality.
20:1 will be incredibly light, almost like skiing through nothing but air. When the ratio is this high, the snow feels lighter because the new snow contains a lot of air rather than tightly-packed snowflakes.
15:1 will offer some faceshots and feel pretty light
10:1 will be fun but feel a little heavy
While there are average snow-to-liquid ratios for each region of the world, every storm is different, so there is no single number that works for each mountain all of the time.
Find the “Snow Ratio” forecast under the “Snow Summary” tab on any location screen by going into the 5-day hourly or 10-day forecast sections.
What Controls the Snow Ratio?
Temperature is the main factor that determines the ratio.
The lightest snow is usually created by temperatures that are roughly between 0°F and 10°F. This is the temperature where snowflakes are being created, usually in the cloud near or above the top of the mountain. This temperature range is called the "Dendritic Growth Zone" and is the favored range for big, beautiful dendrite snowflakes to form.
The amount of moisture in the air also plays a role in determining the snow-to-liquid ratio because it impacts the type of snowflakes that form. The following chart shows the various shapes of snowflakes created by a range of temperatures (bottom axis) and humidity levels (vertical axis).
The wind speed is the final factor that determines the ratio.
A faster wind will knock snowflakes into each other, breaking the flakes and allowing them to pack more tightly together on the ground with less air space in the snow. This decreases the snow ratio and the new powder can feel thick and heavy.