Red Light, Green Light

Before I head into the backcountry, I check the Colorado Avalanche Information Center's avalanche forecast for the zone I will be skiing. Here's what today's CAIC Danger Rose for the Front Range Zone looked like:

The Danger Rose is a quick, visual representation of the backcountry avalanche danger. The rose represents slope aspect and elevation, and the colors represent the danger ratings for those slopes and elevations. Today's forecast was CONSIDERABLE (Level 3) near and above treeline on N-NE-E-SE aspects. Elsewhere the danger was MODERATE (Level 2)

We skied an E-NE aspect at treeline - in other words, a CONSIDERABLE slope. This means that dangerous avalanche conditions exist and that human triggered avalanches are likely. I'd like to explain my decision making process on today's tour and how I came to be comfortable skiing such a slope.

I tend to think of information and observations about terrain, snowpack, and weather as either green lights, yellow lights, or red lights. Taken together, I form an overall green light, yellow light, or red light opinion about avalanche danger.

Before I left the parking lot I knew a few things. Snowfall totals this season have been below average, which results in weak, rotten snow (known as depth hoar) buried at the bottom of the snowpack. This has been a persistent problem all winter and and will continue to be problematic until spring (yellow light). I knew the avalanche danger in the area I was skiing was CONSIDERABLE (yellow light). There was approximately four inches of new snow on the ground (yellow light) and the wind was blowing (yellow light). I was beginning to form an opinion before I even put on my skis.

While my ski partner and I (plus Rangerdog) skinned up the valley, we hunted for additional observations to help us paint a fuller picture of the avalanche danger around us. We saw a west-facing slope with recent natural avalanche debris (another yellow light).

An excellent potential ski mountaineering line

Further up the drainage we eyed our E-NE slope. Scott and I noticed avalanche debris in a gully on looker's left of the slope (yellow light). Scott measured the average slope angle in the high-20s, but the top of the slope was likely in the mid-30s. Mid-30s slopes are great ski slopes, but those slope angles are also prime avalanche terrain. This was unquestionably red light terrain.

The slope in question

We dug a snow pit to evaluate the snowpack and perform stability tests. Our initial compression test and extended column test results both showed the snowpack was not reactive. Scott and I read this as a  "not-red light." In other words, while our tests did not show instability, they also did not prove stability. The snowpack can vary tremendously over very short distances, and it only takes one pocket of instability to create an avalanche and kill you. We cautiously continued up the slope and constanted re-evaluated stability by probing the snow with our poles, attempting to get the snow to slide on test slopes, and digging hasty pits with our hands along the skin track. None of our observations indicated instability. In our minds, this meant we could continue up the slope and test the snowpack further.

Halfway up the slope we reached a rollover with a measured slope angle of 37 degrees. Thirty seven degrees just so happens to be the single slope angle responsible for the most avalanches. This was a major RED LIGHT. We both dug snow pits and performed stability tests. I performed an extended column test with a result of ECTP 21 Q2 @ 120cm. Scott's compression test showed no signs of instability. Green lights. We decided to continue on.

Above the roll the slope measured in the high-20s (green light). However, we were approaching treeline and the snowpack was noticeably wind affected (yellow light). We avoided another small rollover (36 degree slope angle - RED LIGHT), pulled skins, performed a beacon check, and discussed our strategy (Scott would ski first and stop before the 37 degree rollover, I would ski down to him, then he would ski the bottom pitch and I would follow).

Professional avalanche education, years of experience, a skilled partner, and the collection and synthesis of dozens of observations led Scott and me to believe that the slope we were about to ski was avalanche safe.

Part art, part science, and the best powder turns of the year!

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