WeatherFanatics: PHOTOS: Rare, Dense Fog Engulfs Grand Canyon

Tuesday, December 3, 2013

PHOTOS: Rare, Dense Fog Engulfs Grand Canyon

By Samantha-Rae Tuthill, AccuWeather.com Staff Writer

December 3,2013; 9:20PM,EST

Erin Whittaker/National Parks Service. See larger image below.

In a rare occurrence that only affects the area about once a decade, the Grand Canyon was filled with a dense, white fog to end the month of November. The phenomenon was caused primarily by a temperature inversion, but AccuWeather.com Meteorologist Andy Mussoline explained that a few factors came together to cause this event.
"First, there was higher-than-normal moisture in the canyon," he said. "There was 0.75 of an inch of liquid precipitation that fell between Nov. 20 and Nov. 24 at the Grand Canyon National Park Airport [both snow and rain]. Normal precipitation during that time is only 0.19 of an inch, which converts to nearly 400 percent of normal precipitation within about a week of the event."
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Additionally, the average high temperature for this time of year is about 48 degrees Fahrenheit, which means there would be less evaporation of that precipitation than there would be in the summer months. This allowed more moisture to stay in the air inside the canyon.
"A high pressure system settled into the region late last week and allowed for clear skies and calm winds, two important weather conditions that allow the air near the ground to cool rapidly," Mussoline said. "The rapid cooling of the ground allowed a temperature inversion to form."

Typically, air warms as it descends. When the opposite occurs, it is known as a temperature inversion.
A temperature inversion occurs when the air warms with height. The inversion trapped the enhanced moisture in the canyon, and when this moist air cooled at night, it allowed the fog to form.
A temperature inversion such as this occurs a couple of times a year for different areas in the canyon, typically in the winter. It is especially rare for it to envelope so much of it at once, however.

(National Parks Service)
Erin Whittaker with the National Parks Service wrote of the Grand Canyon National Park Facebook page that the fog would burn off with the daytime sun, giving visitors a chance to peer into the vast canyon.

"Freezing fog dominated yesterday and is reflected in great patterns on this Kaibab Limestone," wrote Erin Whittaker of the National Parks Service. (NPS/Erin Whittaker).