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WEATHER LAB | Explaining what graupel is

Sometimes described as soft hail, this wintry precipitation is fairly uncommon but can occur in Iowa when conditions are right.

DES MOINES, Iowa — When you think winter precipitation, your mind immediately goes to snow, sleet and freezing rain.

But what about graupel?

Graupel—a snowflake coated with ice— is not very common, but does occasionally fall in Iowa. 

Here's how it forms

Graupel begins as snow high up in the clouds.

The snow then falls into a layer of supercooled water droplets. These are droplets that exist as a liquid even though the air around them is below freezing.

When those droplets make contact with the snowflake, they immediately freeze or rime.

This results in tiny, white pellets that resemble Dippin' Dots. They are sometimes referred to as small hail or ice pellets.

Unlike hail, they are soft, crushable and cause no threat for damage or injury.

Graupel is often confused with sleet because both tend to bounce when they make contact with the ground.

You can tell the difference between the two by their color. Graupel is milky white while sleet is usually clear.

Graupel usually occurs when temperatures are near or below freezing, but can occasionally occur when surface temperatures are in the 40s.

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