LA CROSSE, Wis. (WXOW) - Many woke up Sunday morning to a frosty and icy wonderland! What many often times mistake as hoarfrost can actually be a phenomenon called "rime ice." While they look very similar, the process of how they form is what's different.
Rime ice often times forms in dense freezing fog, like we all saw last night. It is when supercooled water in the fog (water that is still liquid but below freezing) freezes on contact with the surface and turns to ice. Rime ice can often look like fragile ice needles when up close. It sure is fascinating!
Hoarfrost is when gas (water vapor) turns to ice without passing through the liquid phase. It generally forms on clear, cold and humid nights with little wind.
Given our regional conditions with dense fog last night, I am going to say that most pictures I've seen from today are examples of rime ice.
-Meteorologist Warren Sears