Freezing Fog by Lyndsay Tapases

Fire Bush coated with frost. Courtesy of Graham L. Wiatt

This past Monday morning, many of us woke up to what looked like a Winter Wonderland! At a first quick glance, the landscape may have appeared to be covered in snow. But it was actually just a very heavy and thick frost, which was produced by the development of freezing fog the night before.

Freezing fog is not a term we use fairly often. Freezing fog and regular fog form under similar conditions, but with one important difference: the temperature of the droplets that make up the freezing fog must{}be below 32.

Fog is formed by lots of tiny water molecule droplets that are suspended in the air. These droplets are typically above 32. But water can remain in the liquid form at temperatures well below freezing. These liquid drops cannot solidify, or turn into ice, on their own, and instead need a surface to freeze upon. We call these droplets "supercooled".

When freezing fog forms, these supercooled droplets are suspended in the air. Once they come into contact with a sub-freezing surface (cars, grass, roads, etc.) the drop freezes onto the surface it touched. This is what happened Monday morning, creating the icy wonderland many of us woke up to. It wasn't snow, but it was still pretty.

To the left are a few pictures sent in from our viewers.