CROOKSTON, Minn. — A photograph of a strange-looking cloud taken in Crookston Tuesday afternoon, May 7, by Tom Helgeson and Kumiko Dahl appears tornado-shaped, but looks can be deceiving.

Too wispy and calm to be a tornado, the photo shows cirrus clouds with mare's tails (the trailing striations). What likely happened was a jet flew through a layer of high humidity at about 30,000 feet or so and the exhaust provided condensation nuclei for cloud particles to form in the cold, dry air at that altitude. Because of the high humidity, the ice crystals started to fall from the jet trail — essentially snow. The crystals then got blown around by the wind at that level.

The cloud lingered in the air because of very high humidity and cold temperatures at that altitude, a precursor to the clouds that would build into the region later Tuesday as rain spread across the southern part of North Dakota.

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Photo by Tom Helgeson