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Graupel is often mistaken for sleet or small hail, because the appearance is quite similar. These tiny ice pellets originate from snowflakes. As the flakes fall, supercooled water droplets cling to them and freeze, forming small round or conical grains of ice.
"There's a key difference between graupel and sleet,” explains weather.com senior meteorologist Jon Erdman. “Sleet is precipitation that starts as snow, melts completely while falling, but then refreezes into a pellet by the time it hits the ground. It tends to bounce or make a 'ping' sound when it hits, say, your driveway or car top. Grapuel, however, forms when water droplets freeze onto a snow crystal. It doesn't ping when it hits the ground and may resemble Dippin' Dots ice cream."
This week, graupel has been reported across the northern tier of the U.S.
Graupel is usually white or opaque and only 2 to 5 millimeters in diameter.
Unlike hail, graupel is fragile and usually melts or disintegrates when handled.
Graupel can fall with surface temperatures as warm as 45 degrees, which explains why many people confuse it for hail. However, higher in the atmosphere where graupel forms, temperatures are well below freezing.
Graupel is mostly harmless but can cause roads and bridges to become slippery. Drivers should use caution when any type of frozen precipitation falls from the sky.
