Secrets of the Greatest Snow on Earth
Weather, Climate Change, and Finding Deep Powder in Utah's Wasatch Mountains and Around the World
By Jim Steenburgh
University Press of Colorado Copyright © 2014 the University Press of Colorado
All rights reserved.
1 The Secrets
On December 4, 1960, the legend was born. Inspired by a recent visit of the Ringling Bros. and Barnum & Bailey Circus, a young editor named Tom Korologos opened a special ski edition of the Salt Lake Tribune's Home Magazine with the headline "The Greatest Snow on Earth" (figure 1.1). Tom exclaimed, "Intermountain folk will tell you that the winds blowing from the west leave the wet, sticky snows in the Sierras. When the storms reach the Intermountain ranges, only the most perfect dry powder is left. That's just a sprinkling of what you'll find in this vast, scenic country that is the Intermountain area. And what an area. It's some 600 miles long and 2½ miles high. That's the extent of the Intermountain's big top which supports this real, true Greatest Snow on Earth."
The State of Utah began using Greatest Snow on Earth as a slogan in 1962 and engraved it on license plates in 1985, winning a plate of the year award from the Automobile License Plate Collectors Association (figure 1.2). Utah's trademark on the slogan survived a court challenge from the Ringling Bros. and Barnum & Bailey Circus in the 1990s; the courts ruled that Greatest Snow on Earth doesn't dilute the circus's slogan. But was Tom Korologos right? Is Utah's snow really the greatest on Earth?
No scientist can answer that question. The greatness of snow, like beauty, is in the eye of the beholder. There is no doubt, however, that skiers and snowboarders believe there is something special about Utah snow. Utah ski areas, especially those in Big and Little Cottonwood Canyons southeast of Salt Lake City (figure 1.3), are perennially ranked at or near the top for powder in North America. Alta and Snowbird in upper Little Cottonwood Canyon are frequently co-listed as number one.
What makes the snow in Utah so special? Many people believe, as suggested on the Alta Lodge website, that "it is a scientific fact that Utah's snow is lighter and drier." Others argue that the snow in Utah is superior because of the Great Salt Lake or the drying influence of upstream deserts. However, these are not the secrets of the Greatest Snow on Earth. It turns out that Utah snow isn't even the lightest and driest in the United States.
Snow Water Content
The density of snow depends on its water content, the percentage of the snow that is frozen or liquid water. Light, dry snow has a low water content, is fluffy and easy to shovel, and is a breeze to ski through (figure 1.4). Heavy, wet snow has a high water content, is dense and difficult to shovel, and is often more challenging to ski. Meteorologists classify new snow as light when it has a water content of less than 7 percent, average when it has a water content of 7 to 11 percent, and heavy when it has a water content of greater than 11 percent. Man-made snow has a water content of 24 to 28 percent, which is why it is great for base building and not much else. After a storm, freshly fallen snow becomes denser with time as the ice crystals settle and the air spaces shrink. By spring, the water content of a settled natural snowpack is usually between 40 and 50 percent.
Determining the water content of new snow requires measuring the snow depth and the snow water equivalent, the depth of the water you would have after the snow melts. To measure new snow depth, a white, wooden board is usually placed on the ground or snowpack in a wind-sheltered area prior to a storm (figure 1.5). During or immediately after the storm, snow-depth measurements are made on the board with a ruler or using an ultrasonic snow-depth sensor, a clever device that bounces sound waves off of the snow surface to measure the snow depth. To obtain the snow water equivalent, one collects and melts down (or weighs) a snow sample from the board. The ratio of the snow water equivalent to the snow depth expressed as a percentage is the water content. For example, if the snow water equivalent is an inch and the snow depth is ten inches, then the water content is (1/10) x 100% = 10%.
Snow measurement sounds straightforward, but is difficult in practice. Snow depth and water content can vary dramatically over short distances, especially if the wind is blowing. Take some snow measurements in your yard during a windy snowstorm and you'll see what I mean. Another issue is the frequency of measurement. Snow settles with time, which decreases the snow depth and increases water content. Four measurements collected every six hours and added will yield a greater total snow depth and lower water content than a single measurement collected at the end of the twenty-four-hour period.
As a result, snow-depth and water-content reports are not precise and are sometimes quite poor. An overenthusiastic ski area can easily game the system by taking frequent observations or sampling in locations that collect the most snow. Even observations collected by meteorologists and snow-safety professionals (women and men involved in the study, forecasting, and control of avalanches) are subject to errors and are sparse in coverage. Nevertheless, the data that are available, while not perfect, allow us to evaluate if Utah snow is unusually light and dry.
Snow Water Content in the United States
Observations collected by National Weather Service volunteers show that the average water content of new snow in the United States varies regionally (figure 1.6). In the western United States, snow with the highest average water content falls in the Pacific states, which include the Cascade Mountains and Sierra Nevada where the snow is known as Cascade concrete or Sierra cement. These mountain ranges feature a maritime snow climate with mild temperatures and heavy snow. Snow with the lowest average water content falls over portions of Montana, Wyoming, and Colorado, where it is often called cold smoke, champagne powder, or blower pow. These areas feature a continental snow climate characterized by low temperatures and light snow. Utah lies between these climate regimes and has a transitional snow climate. As a result, the snow in Utah has a lower water content than that found in the Pacific states but a slightly higher water content than that found in Montana, Wyoming, and western Colorado. The average water content of Utah snow is also comparable to or slightly higher than that found in the snowbelts near the eastern Great Lakes.
Remember that these are average values and snow water content can vary significant from storm to storm and even during storms. It is possible to ski champagne powder in the Cascades and Sierra or concrete in Utah and Colorado. However, a greater fraction of the snow that falls in the Cascades and Sierra has a high water content, whereas a greater fraction that falls over the interior western United States has a low water content.
Snow Water Content at Alta and Other Mountain Locations
The analysis above suggests that Utah snow is not unusually light and dry, and this is confirmed by snowfall observations collected by snow-safety professionals at Alta ski area, the gold standard for powder skiing in Utah, if not the world. During the ski season, which runs from November through April, the average water content of new snow at Alta is 8.4 percent. By month, the average water content of new snow is slightly lower from December through March and slightly higher in November and April (figure 1.7).
How does this compare to other mountain locations in the western United States? It is certainly lower than that found in the maritime snow climate of the Cascade Mountains and Sierra Nevada. For example, at the Central Sierra Snow Lab in the Sierra Nevada, the average water content of new snow is about 12 percent, which means that Sierra cement is about 1.5 times denser than Utah's Greatest Snow on Earth. On the other hand, the water content of new snow at several mountain sites in the Tetons and the Colorado Rockies is 7.2 — 8.2 percent, lower than that at Alta (figure 1.8). An exception is the 10.3 percent observed at Wolf Creek Pass in southwest Colorado, where warm, southwesterly flow impinging on the San Juan Mountains frequently produces higher water content snow.
Although there is some uncertainty in these numbers, given the difficulties of measuring snow depth and water content, they clearly debunk the myth that Utah snow is the lightest and driest. However, it is also a myth that dry snow produces the best deep-powder skiing.
The Secrets of Great Powder Skiing
Legendary avalanche researcher and powder skier Ed LaChapelle knew more about snow than anyone. While an avalanche hunter at Alta, Ed recognized that "the best deep-powder skiing is not found in the lightest snow, but rather in snow with enough 'body' to provide good flotation for the running ski" (Lachapelle 1962). In other words, there's more to great powder skiing than light, dry snow.
There are actually three ingredients necessary for great powder skiing. The first is the amount of new snow. This is obvious, but how much is needed? For real powder skiing, the skis or snowboard must float in the new snow. The powder must be bottomless so that your skis or snowboard do not ride on the underlying surface. Taos ski instructor Lito Tejada-Flores suggests in his 2006 book Breakthrough on the New Skis that real powder skiing requires at least a foot of new snow. This is a pretty good estimate, but for our discussion, I'll use ten inches as the minimum snowfall required to qualify as a deep-powder day at a ski area. This lower threshold reflects the proliferation of fat skis and snowboards, which float more easily than the narrow skis of yesteryear. However, there is also an upper limit, known as "too much of a good thing." Huge storms create dangerous avalanche conditions, forcing the closure of steep terrain at ski areas, and the deep snow makes it difficult to maintain momentum when skiing or snowboarding lower-angle slopes or to break trail in the backcountry (figure 1.9a). The best powder skiing comes in Goldilocks storms: those that aren't too small or too big, but just right (figure 1.9b).
The second ingredient is a soft underlying surface. Deep-powder skiing is possible with less than ten inches of snow if it falls on settled powder from a previous storm. Such conditions are rare, however, at ski areas, which are usually tracked out each day, but can be found outside the area boundaries in the backcountry. In contrast, ten inches of new snow might not be enough for bottomless skiing if the snow is bone dry and falls on a hard packed or icy snow surface. When such dust-on-crust conditions exist (figure 1.9c), the skiing looks great, but your skis and snowboards sink right through the dry powder and ride on the underlying hardpack.
The third ingredient is a right-side-up snowfall, which means that lighter snow sits on top of heavier snow. This vertical profile of snow water content is critical for great powder skiing because it helps skis and snowboards float. Right-side-up snow is often called hero snow because the skis or snowboard float easily, turns can be made with little or no effort, and skiers and snowboarders feel invincible. On the other hand, in an upside-down snowfall, heavy snow sits on top of lighter snow. Skis tend to dive and remain submerged. Fat skis and snowboards help in these conditions, but turning is more difficult and requires a more refined technique.
It is the vertical profile of snow water content and not the average water content that determines the quality of the powder skiing. Imagine two storms, each with an average snow water content of 8 percent. The storm that starts with 12 percent snow and ends with 4 percent produces a right-side-up snowfall and sublime powder skiing and snowboarding conditions. The storm that begins with 4 percent snow and ends with 12 percent produces an upside-down snowfall and difficult skiing and snowboarding conditions.
Knowing these ingredients, we can design the ultimate powder climate. We want abundant, high-quality, natural snowfall with frequent storms that produce at least ten inches of snow. We also want storms that produce right-side-up snow for ski flotation. The snow climate found in the Cottonwood Canyons of Utah's Wasatch Mountains has these ingredients in spades, as illustrated by meteorological records from Alta at the top of Little Cottonwood Canyon.
Alta's Snow Climate
Alta is one of the snowiest ski areas in the world, with an average annual snowfall of about 510 inches at the base. Nearby Snowbird, Brighton, and Solitude, which along with Alta comprise the major ski areas in the Cottonwood Canyons, lag only slightly behind (see chapter 2). The snow in the Cottonwood Canyons is not the world's driest, but it is certainly high quality and remarkably consistent. From December through March, the average monthly snowfall at Alta is between 76 and 84 inches (figure 1.10). That equates to an average of just over a foot every five days. Snowfall is only slightly lower in the shoulder months of November and April.
Alta averages eighteen days per season (November to April) with at least 10 inches of snow, or about one deep-powder day every ten days. This is a mind-boggling number that reflects a high frequency of Goldilocks storms that are just right. Most regions that feature drier snow see far fewer deep-powder days. For example, Berthoud Pass, one of the snowier locations in Colorado with an average annual snowfall of almost 400 inches averages only four days with at least 10 inches of snow per season. Alta and the other ski areas in the Cottonwood Canyons do see storms that produce "too much of a good thing" or the occasional drought, but the frequency of Goldilocks storms is quite high.
Notable Snow Events in the Cottonwood Canyons
January 22, 1964: Brighton ski area receives 35 inches of snow, Utah's largest observed twenty-four-hour snowfall to date.
January 24 — 30, 1965: A multiday storm produces 105 inches of snow at Alta.
October — December 1976: One of the worst starts to a ski season in Utah history, with Alta observing only 26.5 inches of snow through the end of December. Even today, locals scornfully refer to the 1976 — 1977 season as "the drought year."
July 1982 — June 1983: Alta observes 847 inches of snow, the largest July to June total ever observed in Utah.
December 1983: Alta observes 244.5 inches of snow, establishing the state record for snowfall in a month.
November 22 — 23, 1992: Alta receives 45 inches of snow in twenty-four hours, establishing a new state record for twenty-four-hour snowfall.
January 4 — 5, 1994: Alta observes the current state record twenty-four-hour snowfall with 55.5 inches of snow with a water content of 5.7 percent.
November 22 — 25, 1994: A four-day storm with periods of lake effect produces 92 inches of snow at Alta and 64 inches at Snowbird.
January 14 — 16, 1995: A three-day storm dumps 100 inches of snow on Alta in sixty-eight hours.
November 22 — 27, 2001: The "Hundred Inch Storm" produces 108 inches of snow at Alta, including 100 inches in 100 hours over Thanksgiving weekend. With only 10 inches of snow on the ground before the storm, Alta wasn't open prior to Thanksgiving and couldn't open during the holiday weekend due to "too much of a good thing."
October 2004: A remarkable October brings more than 100 inches of snow to the upper Cottonwood Canyons. The Utah Avalanche Center issues its earliest advisory ever on October 20 and Brighton opens on October 29 with a 59-inch base.
May 17 — 20, 2011: The average snowfall in May is only 27 inches, but this late-season storm dumped 37 inches on Alta.
But there is more to the story. At Alta and other Wasatch Mountain ski areas, the climatology favors storms that produce right-side-up snowfalls. In the Wasatch Mountains, snow water content is strongly related to temperature and is typically higher when it is warmer and lower when it is colder. Storms that start warm and get colder with time tend to produce right-side-up snowfalls. Conversely, storms that start cold and get warmer with time tend to produce upside-down snowfalls. On 65 percent of the days that produce ten inches or more of snow at Alta, the temperature at mountaintop level (about 10,000 feet) decreases. On 39 percent of these days, it decreases more than 5°F, whereas on only 18 percent of these days, it increases more than 5°F. In other words, the storm climatology at Alta and in the Cottonwood Canyons is biased to produce lots of right-side-up snowfalls and few upside-down snowfalls.
Thus, the secrets of the Greatest Snow on Earth are abundant natural snowfall, frequent Goldilocks storms, and storm characteristics favoring right-side-up snowfalls. How the climate of Alta compares to the rest of the Wasatch Mountains and other regions of the world is the subject of our next two chapters.
2 Wasatch Microclimates
Utah's powder reputation is built primarily on the snow climate found in the Cottonwood Canyons, a fact that was apparent to the earliest Wasatch skiers. In 1935, meteorologist and backcountry skier S. D. Green predicted that "skiers will eventually find that the Brighton Basin, or the heads of the [Cottonwood] canyons within a short radius of this winter paradise, offer the best skiing to be found in the Wasatch Mountains" (Kelner 1980, 155) (figure 2.1). Green was right. The Cottonwood Canyons are the climatological sweet spot of the Wasatch Mountains, with their own microclimate that produces more snow than falls in the surrounding area. On any given day, understanding the microclimates of the Wasatch Mountains can help you find the deep powder, sunshine, or spring snow that your heart craves.
Little Cottonwood Canyon
Little Cottonwood Canyon, home to Alta, Snowbird, and extensive backcountry terrain, penetrates eastward into the Wasatch Mountains from the Salt Lake Valley (figure 2.2). It is a steep glacier-carved canyon surrounded by mountains that reach to over 11,000 feet, including the 11,498-foot American Fork Twin, the highest peak in the central Wasatch Mountains. Although Mount Timpanogos and Mount Nebo in the southern Wasatch Mountains are slightly higher, the high terrain surrounding Little Cottonwood Canyon is the most extensive in the Wasatch Mountains. (Continues...)
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