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Understanding where 'freezing fog' comes from

A rather dense area of freezing fog shrouded nearly all of Northeast Kansas on Tuesday morning. That left much of south facing trees coated in a white frost-like ice.

The wind was light, but out of the south, while the fog moved through. That south wind allowed for south-facing trees and surfaces to coat with a very loose riming of ice.

Loose ice allows for air to be essentially "trapped" within the ice structure, giving it a white appearance rather than a glazing of ice, which is clear.

This reminded me of a word that is rarely used. Hoarfrost. It is a very thick, very loose frost that appears very much like what this morning's freezing fog looked like. It's formed on clear, very cold nights where a thick, but loose frost forms on exposed objects.

Again, that's not what we had this morning. It was a true freezing fog. Whatever you call it, it was a beautiful scene across our corner of the state this morning.

January 12, 2010

Weather Watch


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