Editor’s Note: This is a weekly column written by Meteorologist Joel Gratz that will take you “behind the scenes” of the typical weather forecast. Joel is the founder of ColoradoPowderForecast.com, where you can sign up for his email alerts.

Boulder, CO – Last Saturday, Dec. 18 was a secret powder day around Colorado. Despite a forecast for two to four inches at most locations, 10-15 inches of “blower” powder fell throughout the day. What a double-edged sword! Of course I love powder and am happy that folks on the hill experienced faceshot after faceshot of super light snow. But on the other hand, how did the atmosphere out-wit the meteorologists yet again?

The main thing that the weathermen got right was the abundant moisture streaming into Colorado all the way from Hawaii. This moisture arrived overnight Friday into Saturday morning and was the reason why we forecasted a few inches of snow through the beginning of the weekend.

The aspect that the weathermen got wrong was the cold air that was trapped around the mountains. Usually, moisture from Hawaii also brings warm air, and this type of air is not as efficient at converting moisture into deep, fluffy snow. However, somewhat colder air was stuck around the mountains of Colorado from a previous storm, and it’s this type of air that efficiently converts moisture into blower powder.

By the time we (I) realized what was going, the powder was already piling up across the state, proven by the PowCam at Crested Butte.

(photo: Crested Butte Mountain Resort)

Often times the forecast isn’t materially different from what actually happens, but there are a few days that surprise even the most experienced forecaster. Sometimes a bit of luck is all it takes to convert a two- to four-inch mundane Saturday into a foot-plus memorable storm skiing day. While I like to be correct in my forecasts, I wouldn’t mind another few secret powder days.

Joel first fell in love with weather and skiing at age four, and this passion for snow has not faded with age. After earning his Meteorology degree from Penn State in 2003 and a Masters from the University of Colorado in 2006, Joel started Colorado Powder Forecast out of Boulder, Colo., to help fellow snow lovers with accurate and entertaining weather forecasts.