Correction: The original version of this article described the ice photographed at Shenandoah National Park as hoar frost. While it resembled hoar frost, it is more accurately described as rime ice, as the updated version of this story discusses.
What happens when the air near the ground is super foggy and freezing cold at the same time? Ice can build up on all kinds of surfaces and, under just the right conditions, create a magnificent scene.
A week ago, a gorgeous display of such ice coated the vegetation at Shenandoah National Park. Photographer Tyler Reber was there to document the spectacle.
“I got to see something that I’m not sure I’ve ever seen before,” Reber posted to Facebook. “Shenandoah National Park hit temps right around freezing and simultaneously was quite foggy in spots. The fog was freezing to surfaces as it was moving through. . . . Such a cool sight to see.”
The air over the Mid-Atlantic was saturated following a cold, rainy storm the previous day. Temperatures in the D.C. metro area fell to 35 to 40 degrees the morning of Nov. 8 in the storm’s wake, but the mercury settled near freezing in the mountains.
As fog developed in the freezing air and light winds gently nudged the fog into vegetation, the suspended water vapor froze into ice on contact. Because the air was so moist, the ice was able to build-up into thick coats on the windward side of both trees and shrubs.
In some places, the soft rime and its whiskery appearance resembled what is known as hoar frost but formed under different atmospheric conditions. Hoar frost usually forms on clear cold nights, when moist air is trapped near the ground – either due to recent fog or snow cover.
“Hoar” is an Old English term meaning “venerable, old,” and the Old English dictionary describes the frost as resembling an old man’s beard, according to the National Weather Service.
The National Weather Service wrote hoar frost can form when “ice crystals are deposited directly from a fog made of ‘supercooled’ vapor,” when water droplets are cooled below freezing but remain liquid. “It is essentially the same process as dew formation, except the surfaces upon which the dew would form are frozen and the ‘dew’ is sub-freezing as well.”
Find Reber’s gorgeous series of rime ice photos below.