By Ian Hoyer EBS COLUMNIST
When avalanche conditions are dangerous, staying off steep slopes is an important piece of staying safe while riding in the mountains, but it isn’t enough.
For an avalanche to break, some part of the slope has to be steeper than 30 degrees. However, that doesn’t mean you’re safe if you just stay off those steep slopes. Avalanches can be triggered from lower-angled (or even flat) slopes and break above you, below you or sometimes hundreds or thousands of feet away. If you’re too close below a steep slope when you trigger an avalanche, that avalanche is going to run downhill and hit you from above. Depending on how big that slope is, the snow could be moving 60-80 mph by the time it hits you. When the snow stops moving, it’ll pile up on top of you, burying you deeply near the bottom of the debris. An avalanche airbag pack won’t help much, because you won’t be tumbled far enough for it to do its job and push you towards the surface. If all this sounds like crossing beneath steep slopes can be dangerous, that’s correct—it is.
An avalanche earlier this season near Cooke City demonstrates these dangers well. The avalanche occurred first thing in the morning on Dec. 11. There were feet of fresh snow following the first big storm of the season. There had been avalanche warnings issued the previous two days. Snowfall had stopped the previous afternoon and avalanche danger remained “Considerable.”
A group of two riders left town, rode up to Daisy Pass and one of the riders dropped over the back side. He was the first rider to cross the pass this day (and likely the first in several days). His route was not in steep terrain, but it did cross beneath the steep northeast face of Crown Butte. As he descended, he triggered a big avalanche that broke 800 feet uphill of him, 500 feet wide and 4-6 feet deep. He was fully buried beneath 2-3 feet of snow, but luckily was wearing an avalanche transceiver and was located and dug out quickly by well-prepared onlookers. A happy end to the story, but one that wasn’t at all assured.
So, what happened? I have personally dropped over Daisy Pass dozens, if not hundreds, of times. There are many times when it is a totally reasonable route—except not on that day. It just wasn’t the day to be crossing underneath steep slopes. When avalanche conditions are dangerous, particularly if there are weak layers buried at the base of the snowpack (as there were on that day), you’ll want to avoid all avalanche terrain. That means steep slopes, but also means the runout zones beneath them.
How can you know conditions are dangerous? Reading your local avalanche forecast is the easiest way. The avalanche forecast will tell you when you are likely to trigger avalanches and will also highlight when you’re most likely to be able to trigger slides from the below. When these conditions exist, stay far away from steep slopes. If it isn’t possible to stay out of the runout zone, choose a different area to ride where there isn’t any hazard above you and come back when conditions are less dangerous.
You can find your local forecast at avalanche.org.
Ian Hoyer is a forecaster with the Gallatin National forest Avalanche Center.
