One of the coolest parts of a spring snowstorm is the snowflakes, which are often much bigger than winter flakes and make the snow feel almost magical. But as temperatures warm, it turns out the size of the flake is not so much magic, but the science of the season.

Snow Formation

Snow is pretty cool (no pun intended). It forms in clouds, high up over our heads. Tiny ice crystals in the clouds bump into each other and stick together. As more and more stick, the growing flake gets too heavy for the rising air within the cloud to hold it up. When this happens the perfect little snowflake falls from the cloud and drifts down to the ground below.

Temperature

Temperature plays a major role in precipitation. If it is warm enough, the ice crystals falling from the sky melt. If they melt completely, we get rain. But that happens all summer long. The interesting thing is what happens when those ice crystals don’t melt all the way.

Temperature depending snowflakes form into many different shapes and sizes. Plates and columns are the two basic categories of flake type. As temperatures approach freezing (32 degrees Fahrenheit), snow forms into a thin, branch-like ice crystal called dendrites. If dendrites melt before falling to the ground, something interesting happens.

Big Flakes

As we’ve seen in recent days, snow falling when temperatures are above freezing isn’t uncommon. When temperatures climb above freezing, in the presence of light wind, flakes tend to get bigger.

Snowflakes fall from a portion of the atmosphere that is below freezing to a part that is above freezing, which slowly melts the flakes. The ice crystals that make up the snowflake melt from the outside in. The melting causes a small layer of water to form on the snowflake itself.

The partially melted snowflakes bump into each other falling from the sky and stick together, thanks to that thin layer of water. This happens over and over, with partially-melted flakes smashing together and refreezing into a bigger snowflake.

This process is what creates the massive snowflakes that fill the air each spring. In the right conditions, these super-flakes can reach an inch in diameter.

Heavy Snow

 

Ask anyone with a shovel, late-season snow is often heavier than snow that falls in the winter. The heavy nature is often the reason it's called "back-breaking" or "heart attack" snow. Unfortunately, those names come from the dangers of lifting a wet-shovel-load. 

The melting of flakes as snow falls plays a role in the weight of snow itself. Wet snowflakes compact more than frozen ones. That means, there ends up being more water packed into a smaller area. If you are out there shoveling spring snow, you are actually shoveling something more equivalent to water than someone shoveling the same amount of snow on a cold winter day. 

Don’t Blink

For those hoping for spring, probably the best part of these massive snowflakes is how fast the snow melts. That's because the flakes are already partially melted as they accumulate.

Once on the ground, there are a couple of things keeping the groundcover short-lived. By now the ground has thawed out. Winter’s cold is gone and springtime warmth is trapped beneath the fresh snowpack. From above, the higher angle of the sun means the intensity of the sunshine is greater.

Putting these together — the jump-start on melting, warmth from below and increased intensity from the sun — the rapid melting makes sense. Before you know it, the snow will be gone and leaves will welcome the official start of spring!

 

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