Avalanche avoidance starts now

A few intrepid bootpackers have slogged in to ski Pastoral Glacier, but most backcountry skiers haven’t made it out much, or at all this season. Even if you don’t generally ski much until the holidays and thereafter, avalanche avoidance should start now. The safest way to travel in the backcountry is to understand the whole snowpack, for the whole season, in each mountain range you visit.

Of course, the best way to gain a detailed and accurate understanding of the snowpack is to visit repeatedly and frequently, while watching wind, precipitation, and other weather phenomena (such as overnight faceting caused by clear skies, for example). Since it isn’t possible for working people to do that for Turnagain Pass, Chugach State Park, and Hatcher Pass, it is wise to use the area forecasts as a proxy when you can’t go yourself (cnfaic.org, anchorageavalanchecenter.org, hatcherpassavalanchecenter.org). If you want to travel safely in avalanche terrain, it’s a good idea to read the weather, observations, and avalanche forecasts every single day for places where you intend to recreate.

The weather and observations are as important as the forecast, particularly in the early season. As I write this article, none of the local avalanche information centers are publishing forecasts (though they’ll start soon). However, there’s snow in the mountains, and those early snow layers can have significant effects on safety all season long. Here’s an example: In Hatcher Pass, a significant snowfall before Halloween dropped just enough snow to make backcountry skiing possible around Hatch Peak. One of the groups that went out and skied triggered an avalanche that swept a skier 400 feet down a slope.

How could the skiers have anticipated this avalanche, based on following the weather and (albeit) intermittent reports from the local avalanche information center? First, a significant length of time transpired between the first significant snows and a six-inch storm on Oct. 24. Second, significant winds moved snow around, increasing the likelihood of windslabs. A very thin snowpack increases the number of potential trigger points for an avalanche, which is a particularly difficult issue to manage in areas of irregular talus that are common in Hatcher Pass. Here’s how Hatcher Pass Avalanche Center summed up the early season conditions, shortly before the Oct. 28 avalanche occurred: “The early snow that arrived at Hatcher Pass has rotted out and become a weak base. Rain up to 4,000′ has left a crust layer near the base of the snowpack. Winds transported snow into stiff wind slabs sitting over the weaker basal snow which have recently been reactive.”

Looking back is easy, and looking forward — making our own decisions in avalanche terrain — is harder. But even here, weather information plays a key role. If I’m skiing in Hatcher Pass right now, I’d want to know:

How well has snow since Oct. 28 bonded to the rotted/faceted snows from earlier in the season?Are the slabs that existed on Oct. 28 still reactive?Has there been more wind, and thus more wind slab formation?Have clear, cold nights created new facet layers that will create dangerous bed surfaces after the next snowfall?

The snowpack is a big layer cake. Particularly for areas of thin snow cover like Hatcher Pass, you can’t make accurate decisions without understanding all layers of the snowpack. And you can’t understand all the layers of the snowpack without following weather, avalanche forecasts, and avalanche observations for the entire season.

In some areas, with some condition, early season snow layers can get buried and become inconsequential later in the season. This is frequently, but not always, the case in the heart of the Turnagain advisory zone. But you can’t blindly count on this assumption, because even in Turnagain there can be persistent weak layers that create significant avalanche hazards for months, and these dangerous layers can be formed in the early season.

Watching the snowpack includes monitoring it all week at work--you may not be out skiing, but the snowpack is changing. A facet layer that’s created by clear, cold weather on Monday, might be buried by a storm on Tuesday. This time of year, before avalanche forecasts are out, you’ll need to follow the weather to understand that risk.

And this attention to the snowpack is equally important later in the season. According to the Chugach National Forest Information Center, the majority of avalanche fatalities occur when forecasted avalanche risks are “moderate” or “considerable.” I think the “moderate” forecasts can be the scariest: If there’s a two foot slab, that’s two weeks old, on a bed surface of facets, and six inches below the facets is a rain crust, there might be a relatively small chance of an avalanche in moderate terrain. But if the slope does release, the avalanche could be large, and could step down into older layers.

Superficially reading the avalanche forecast on a Saturday morning wouldn’t provide you with enough information to understand this risk—but you might have a good sense of it if you read the forecast, the observations, and follow the weather every day.