World and Nation

It’s All About The Ratio

It’s All About The Ratio

Meteorologists often describe snow as “wet” and “dry.” An example of wet snow is the kind we just got in yesterday’s storm. It tends to stick to tree trunks and street signs like paste, is hard to shovel, and makes good snowballs to pelt your friends or enemies with. On the other hand, dry snow is quite light and powdery, blows around easily, and makes for great skiing and snowboarding. There are a number of factors that determine whether we get wet or dry snow, but it generally comes down to the type of snowflakes that fall out of the sky and corresponding snow to liquid ratio that results.

Wet snow has snow to liquid ratios that are generally around or less than 10:1. That is, for every 10 inches of snow you melt, you get one inch of liquid. When temperatures are just below freezing, snowflakes tend to take the form of plates, columns, and prisms which compact and stick more easily. Along the coast of MA, we typically see this type of snow. Every now and then, the right meteorological conditions set up and we see snow to liquid ratios that are greater than 10:1 yielding dry snow. When this happens, snowflakes are forming in supersaturated air around 5 F (-15 C) resulting in big fractal dendrites that pile up much faster due to their shape and propensity to trap air as they deposit on the ground.

Extended Forecast

Today: Cloudy in the morning, then clearing in the afternoon. NW winds 10-20 mph. High 37 F (3 C).

Tonight: Partly cloudy. NW winds 10–15 mph. Low 26 F (-3 C).

Tomorrow: Sunny. NW winds 5–10 mph. High 36 F (2 C).

Friday: Partly cloudy. N winds 5–10 mph. High 37 F (3 C).

Saturday: Sunny. N winds 5–10 mph. High 34 F (1 C).