Interactive radar: More rain moving across North Alabama
School Closings across the Tennessee Valley

Spotted This Weekend: Cold Weather Allows Ice Halos To Form

It might be cold out, but there are still some beautiful sights in the Tennessee Valley! This cold air allowed ice crystals to form in high thin clouds, making for the perfect conditions to spot ice halos.

One of the most common halos is the 22° halo, which forms a circle of light around the sun. Ice halos were captured by our viewers on both Friday and Saturday:

For these halos to form, rays of sunlight move through hexagonal shaped ice crystals and are deflected as they move through. The deflection causes the light to come out at a different angle than it went in, causing the halo effect. The smallest angle of deflection is about 22°, which is where the inner part of the halo is found. The different angles of deflection from 22° to 50° create the ‘glow’ that exists around the halo.

At the top of some 22° halos are upper tangent arcs. The columnar hexagonal crystals that create tangent arcs allow light to be deflected from 22° to 60°, allowing the arc to wing out farther from the 22° halo.

Also spotted on Friday was a  sundog, which looks more like a glint or patch of bright light:

Hexagonal plates must be present for sundogs to form. The light that moves through to create sundogs comes in on one side of the plate, is refracted twice, and comes out another side of the plate. This refraction can cause a prism effect to occur, which adds color to the sun dogs (the most common color is red).

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