Earlier in the week we woke up to some beautiful winter scenes with the trees covered in a glorious white frost. Fog, even when temperatures are well below freezing, is usually composed of mostly liquid cloud droplets (supercooled water).
When these liquid droplets touch objects below freezing, ice crystals begin to grow on the colder surfaces. The interlocking ice crystals become attached to branches in trees and other objects and slowly grow into hoar frost. This crystal growth turns trees and any other object that is exposed to these supercooled water droplets white, giving the landscape that classic “winter wonderland” look.
Although this phenomenon occurs several times each winter, the Red River Valley is not as likely as other areas to experience hoar frost because a very light wind is necessary for the crystals to grow to greater lengths and of course, the wind tends to blow lightly locally when other areas nearby are calm.