Weather Talk: Graupel formation requires unique set of conditions

Tuesday morning, there was a light shower that consisted mostly of sleet with a little rain. There were a few snowflakes toward the end. But the highlight for me was the graupel.

Tuesday morning, there was a light shower that consisted mostly of sleet with a little rain. There were a few snowflakes toward the end. But the highlight for me was the graupel.

Graupel is a form of precipitation that is perhaps best described as tiny Dippin’ Dots. It is most often produced in little showers when the temperature is near freezing.

It actually requires a unique set of conditions to form. Snowflakes fall through a layer of supercooled water (water droplets in a liquid form yet below the freezing point) so that the supercooled water adheres to the snowflakes. It produces these somewhat airy, BB-sized balls of a snow-like substance.

Graupel is rarely heavy because these conditions are more common when the humidity is not terribly high. So graupel is sometimes heavy enough to cover the ground but rarely to any depth.

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