Frosty Ferns explained…

Don Dickon says that in his more than 70 years, he's never seen frost spread from the windshield to the car! Find out why:

Making weather is a little bit like baking a cake: you need all the right ingredients for it to turn out! Last weekend, a combination of light winds, cold air and relatively high humidity came together to produce a work of art on Don Dickson’s car.

Frost: is the coating or deposit of ice that may form in humid air in cold conditions, usually overnight.

Frost usually forms when

1)      a surface cools through loss of infrared radiation to a temperature which is colder than the dew point of the air next to the surface,

2)      and when the temperature of that surface is below freezing .  The source of this moisture is water vapor contained in the air.

There are many types of frost. In my opinion, the most beautiful one is fern frost and that’s what covered Mr. Dickson’s car.  Fern frost, also called window frost or ice flowers, for obvious reasons, forms when a glass pane is exposed to very cold air on the outside and warmer, moderately moist air on the inside.  Car windows and paintwork are good heat conductors; they warm up quickly on a sunny day, but release that heat after sunset.  The interior of the car on the other hand, will cool at a much slowly rate. So one side of the window is cold, the other side is not as cold and more humid..et voila! If those same conditions exist on either side of the hood, frost will cover it too!

So how do we explain the elaborate patterns?

Water molecules from the air condense onto rough nuclei – scratches, pits, or dust particles. Once a tiny ice crystal has formed it grows across the cold surface.  Tiny imperfections such as scratches and dust influence the arrangement of the drops of  moisture, so when they freeze, they form beautiful patterns.

Another little masterpiece compliments of Mother Nature!

Chief Meteorologist

Cindy Day