WeatherTalk: Snow measurement is only by accumulation
There is no realistic way to gauge how much snow is in the air before it reaches the ground.
The wet snow that fell across much of North Dakota and northern Minnesota earlier this week was partially melting as it accumulated, resulting in relatively meager snow amounts on the ground. Many people communicated with us in the Weather Center office, wanting to know how much snow "actually fell" as opposed how much accumulated. The answer to this question is disappointing. There is no realistic way to gauge how much snow is in the air before it reaches the ground.
Snow measurement is only by accumulation on the ground. When snow crystals reach the ground, they settle with a great deal of air around them. Average snow accumulation is about ten parts air to one part ice. A dry, fluffy snow accumulation might contain 40 to 50 parts air to one part water. A wet, slushy snow might be half ice and half air. The only ways to measure snow are by ground accumulation or its melted water content.