Frosty Start To Monday

by Kelly Smith, Meteorologist
February 07, 2012 12:10 PM


Monday morning was a picturesque sight as freezing fog formed a frosty coating to surfaces. Tuesday’s KDLT Weather blog explains the common misconceptions of the weather phenomena called: Riming.
Soft Rime is often incorrectly identified as “Hoar Frost”. Hoar Frost and Soft Rime may look similar when coating trees and surfaces, but the processes behind the two are very different. Soft Rime is formed when water vapor condenses into super cooled water droplets and attach to a surface such as a tree branch or fence. In contrast, Hoar Frost is formed on clear nights when there is no fog present, but just high levels of humidity and temperatures below 17 degree’s. Unlike Soft Rime, Hoar Frost is formed by direct deposition of water vapor to solid ice.

Fog started forming in Sioux Falls at 9pm Sunday night, with temperatures below freezing at 25 degree’s. Fog/mist conditions occurred for between 14 and 15 hours with temperatures hovering between 24 and 26 degree’s. 14 hours of fog/mist conditions and temperatures below freezing allowed a great deal of soft riming to occur which resulted in some beautiful pictures. By noon, the fog let up and winds slowly blew away the pretty sight.



(Windward sides of tree's were coated with a soft rime in Sioux Falls Monday Morning. Image Courtesy: Tom Hanson)



(Tree's and Grass covered in a Soft Rime Monday Morning. Image Courtesy: Tom Hanson)



(Freezing Fog Turned South Sioux Falls into an Ansel Adams Picture. Image Courtesy: Kelly Smith)



(Close-Up of the windward side of a tree in Sioux Falls. Image Courtesy: Kelly Smith)

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