Spiky rime crystals coat berries on a bush in a parking lot at a mall in Duluth this afternoon. Bob King
Frost forms when water in the air condenses directly from water vapor to ice and forms carpets of minute crystals that whiten our lawns in early fall. Hoarfrost forms the same way but the grains grow larger to make delicate feathers of ice. Today across parts of northern Minnesota, rime coated trees, poles and even fire hydrants in long pointy needles of ice. Rime ice forms when supercooled water droplets in the air — often suspended in a thin fog — freeze onto surfaces that are 32° F (0° C) or colder. “Supercooled water” is water that’s below the freezing point but still remains a liquid or as droplets.
In this scene you can see widespread rime coating nearly everything in sight. Bob King
I noticed haziness in the air when I stepped outside this morning, but not until I left my neighborhood and drove to a higher elevation (with a lower air temp.) did I see the transformation. Honestly, it was porcupine quills everywhere. Every edge or pointed surface sprouted long needles of the stuff. Despite their spiky ...