Slopes are powdered up and ready to go
November 24, 2008 · Updated 5:12 PM
8:55 in the morning.
Ticket window at Alpental.
26 degrees, lots of wind.
Jan. 1, 2008 — Happy New Year.
That’s how the New Year started for me. Turns out I was very glad I dragged my tired self out of bed, because the conditions that day were as good as it can be in the Pacific Northwest. The entire mountain was either powder or packed powder, not even one single area was icy or scraped off, and with literally no lift lines, there was plenty of mountain for everyone. You could set an edge everywhere, and it was a great day to rebuild one’s ego.
One week later, it isn’t quite the same. Oh, there is plenty of snow alright: We now proudly stand 100-150 percent of normal snow pack, and more snow is headed our way. But there was one tiny little issue last week; for the first time in several weeks, the temperature in the Cascades went well above the freezing level. It was only for a day, which doesn’t seem like much, but with the rain falling and snow thawing, then refreezing, the outdoor enthusiasts encountered a completely different surface condition.
I’m not writing this to complain. No, far from it: the Cascades are really delivering the goods so far this season. But I am going to remind you that we are seeing some very unstable snow conditions, and it is not surprising that the Northwest has already witnessed many avalanches and, unfortunately, several related deaths. And that can just take all the fun out of a day.
In checking with the Northwest Avalanche service at www.nwac.noaa.gov, I wasn’t surprised to read that there had been active avalanche results at Mount Hood Meadows and triggered slabs reported at Mount Baker, near Mount Pilchuk, at Whistler, and that extreme caution was recommended in the backcountry.
So, while the persistent rain has been creating havoc around Puget Sound, the heavy snow falling in the mountains can have its own drawbacks. When the moisture content of the snow pack increases, the odds become greater that one of the biggest hazards to winter recreation — avalanches — will occur. Remember the closings of Interstate 90? You know it will happen, you just don’t know when.
To many skiers, the mere mention of the word avalanche creates a frightening mental picture. Avalanches are complex natural phenomena that are difficult to predict. But understanding the basic types and their contributing factors can help in avoiding potential danger.
Of the two types of slides, the loose-snow avalanche is the least dangerous. These start at a point in a small area, then grow as they descend. The loose snow moves as a formless mass with little internal cohesion.
Most accidents are caused by the more dangerous slab avalanches. This type starts when a large area of snow begins to slide all at one time. Usually, there is a well-defined fracture line where the snow breaks away. Slab avalanches are characterized by the tendency of snow crystals to stick together, and there might be large blocks or chunks of snow in the slide.
Four terrain factors affect avalanches: slope steepness, slope profile, slope aspect and ground cover.
The slab avalanche is most common on slopes between 30 and 45 degrees, and is more likely to occur on convex-shaped slopes than on concave ones. Snow on north-facing slopes is more likely to slide in mid-winter, whereas south-facing slopes are more dangerous in the spring when the sun shines longer. Of course, here in the Northwest, excess sun is a problem some of us would be happy to experience. Lastly, it is probably obvious that a smooth, grassy slope is more likely to slide than rougher terrain.
The major factor contributing to the threat of avalanches is temperature. Storms that start with low temperatures and dry snow, followed by rising temperatures and wetter snow, contain the ingredients for an avalanche. This is because the initial dry snow forms a poor bond and has insufficient strength to support the heavier snow deposited later. It has been reported that about 80 percent of all avalanches occur during or right after a storm.
I once took a one-day avalanche awareness class at Snowbird in Utah. The head of the avalanche team pointed out that, when too much snow falls during a short time, the snow can undergo a change in character due to the compression taking place. Not only does the water content percolate toward the surface, but the edges of the snowflakes themselves become less sharp and more rounded, similar to ball bearings. The result can be snow breaking off and sliding due to this lessening of adhesion.
Avalanche control is accomplished by setting off explosive charges to cause slides when skiers are not in harm’s way. At our local Cascade resorts, these charges are either fired from guns, set by hand, or dropped from aerial trams.
Because ski areas are so diligent about their avalanche control efforts, most natural slides happen outside the confines of resort boundaries. But if you are planning on going out into open country, perhaps cross country skiing, snowshoeing or snowmobiling, you can’t rely on ski area management to do the thinking for you.
Use some common sense. Avoid areas where trees have been pushed over, as this is an obvious sign of prior slides. The safest routes are on ridge tops, slightly on the windward side, or out in the valley, far away from the bottom of the slope. It is probably a good idea to minimize the amount of time spent on open slopes in adverse snow conditions.
The State Department of Transportation works overtime to ensure the safety of the highway motorist. Nevertheless, when I-90 experiences closures due to avalanches, you know the conditions are ripe for slide activity. I’m not an alarmist, but sometimes it is just prudent to stick to groomed runs at an avalanche-controlled resort.
As the Snowbird instructor told me, the number of people who actually become avalanche experts always turns out to be significantly less than those who start out. It is indeed a risky business.
John Naye is a Mercer Island resident and the current president of the Western Region of the North American Snowsports Journalist’s Association. He can be reached by e-mail at firstname.lastname@example.org.