Curious Nature: Surf Powder and Atmospheric Rivers
We love our light and fluffy powder in Colorado and there are plenty of reasons why we are lucky to have “champagne or blowing powder”. In order to plan your perfect day of riding, skiing, sledding or even snow removal, it helps to know the factors that influence snow quality, such as snow/water ratio, temperature, humidity and , finally, the wind.
Light snow is defined as snow with low water content, most easily measured as a ratio. If 15 inches of snow melts and produces 1 inch of water, the snow to water ratio is 15:1. running in the middle of Colorado. -winter. Lower ratios such as 10-1 make snow heavier and are more common in spring or maritime snow climates. The best powder days are the result of a 20-1 ratio and those in the know remember those rare days.
Temperature is the number one weather factor influencing the formation of perfect powder and something we usually check before heading out anyway. The ideal temperature for light snow formation is zero degrees to 10 degrees Fahrenheit. Colder temperatures generally produce less snow while higher temperatures produce a lower snow report.
In Eagle County, temperatures are influenced by a number of factors, including season, geography, and elevation. At an elevation of 8,150 feet, average high temperatures for Vail from January through February are 28 to 33 degrees Fahrenheit and average low temperatures are 5 to 8 degrees. Typical mountain top temperatures in ski areas are even colder, decreasing by 3 to 5 degrees per 1,000 feet of elevation gain, meaning temperatures are usually perfect for light snow formation.
The available moisture contained in passing thunderstorms also influences the formation of desirable powder. In our region of Colorado, northwest flow weather systems are more favorable for snowfall and our snowpack region is defined as continental, away from the influence of ocean weather systems.
For example, a weather front on a northwesterly flow will deposit most of its moisture over the Pacific Northwest, then the mountains of Idaho, Montana, and Utah, and finally reach the Rocky Mountains of Colorado, where snowfall amounts are generally less and storm moisture content is lower. Of course, there are geographic variations such as Wolf Creek Pass, Schofield Pass, and Buffalo Pass, which typically have the highest snowfall in Colorado.
The current more favorable snowpack depth in Colorado is due to the Atmospheric River that formed over the Pacific Ocean off the coast of California in late December. This storm brought both significant amounts of snow and high water content snow.
Ski areas such as Crested Butte and Aspen were the most favored by this model and received over 90 inches of snow during this two week period. Fortunately, Vail and Beaver Creek also received respectable snowfall, and some of them had below average snow to water ratios for this time of year.
Finally, wind has a significant effect on snow during and after snowfall, in some cases more than temperature. Light winds combined with temperatures between 0 and 10 degrees are more conducive to the formation of stellar dendrite crystals, the iconic shape of the snowflake, which lands freely on the ground with a good deal of airspace.
Winds above 15 mph will alter the shape of snow crystals, creating circled or round crystal shapes that pack more tightly on the ground. Once on the ground, the wind can carry snow two to three times faster than the amount falling from the sky, causing further compaction.
High winds during and after snowfall contribute to wind-affected snow and wind slabs. Wind slabs make riding and skiing conditions more difficult and increase the risk of avalanches on steeper terrain, including slopes over 30 degrees, which is similar to a typical blue/black run in our local ski areas.
If you’re familiar with Vail’s Back Bowls, you already know the prevailing wind directions, scouring Forever and creating large ledges over Apres Vous, Genghis Kahn, and Lover’s Leap in Blue Sky Basin. The areas under these ledges often have the deepest snow on a power day, and depending on the wind speed, the quality of the snow varies.
Although we had a bit of a dry spell, we will continue to hope for ideal conditions for blowing powder and face shots. All of this information can be deciphered from popular forecasts such as the National Weather Service, OpenSnow, or local weather Facebook pages.
With a little research, you too can become an expert in blowing powder prediction. There’s still plenty of winter left and given our location and altitude in Colorado, it shouldn’t take more than a few weeks!
Markian Feduschak is the president of the Walking Mountains Science Center and describes himself as a snow geek and an avid skier. Markian is also a board member of Friends of the Colorado Avalanche Information Center, a non-profit organization that supports the Colorado Avalanche Information Center.