Measuring Snow

The other day I had the question from Texas about a 25" snowfall that only accumulated to 4" deep.

So how did they know 25" of snow fell?

Snow measurement definitions and practices have changed and evolved over the years. There are some differing opinions on how you should handle different situations, such as measuring with wind, or when the temperature is hovering around freezing.

At one time in NWS history, observers were taught to estimate the accumulation of snow as if it were not melting when it reached the ground.

This was normally done by estimating an approximate snow to water ratio, then measuring the amount of precip that fell from the melting snow, and then multiplying that amount of precip but the inches of snow per unit amount of water to get a total snowfall estimate.

In the 1990s, many observers and users of snow data decided that was not an appropriate way to report snowfall.

Since then, we report only snow that can be seen to accumulate. If it melts on contact, it does not contribute to a reported accumulation.

So more than likely, in the case of the 25" snow that only measured to be 4" on the ground, they were estimating the accumulation.