What is graupel?

Posted at 4:44 PM, May 01, 2024
and last updated 2024-05-01 18:44:16-04

MISSOULA — You've probably seen a lot of those graupel showers over the past few days.

So, what is graupel? Is it hail? How is it different than hail? How does it form?

All great questions! Let's dive in!

Graupel is not hail, although it can look like it.

Both hail and graupel are balls of ice, however, they form in very different ways.

Hail usually forms from intense thunderstorm updrafts (rising air). Ice crystals high in the clouds are caught in the updraft of a thunderstorm and will continue to grow by colliding with each other and sticking together. They will do this until they become to large and heavy for the updraft to support. Once this happens they fall as balls of ice or hail.

Graupel starts out as a snowflake high in the atmosphere. As it falls, it falls through a layer of the atmosphere with super cooled water droplets.

So, what are super cooled water droplets? Good question! Super cooled water droplets are drops of water that are remaining liquid even though their temperature is below 32° or freezing.

As the snow flake falls into this zone, the water droplets attach to it and immediately freeze. This creates a thin layer of ice around the snow flake creating what we know as graupel!

So, next time you see those dip and dots falling from the sky, hopefully you have a better idea of what they are!