Why 'Considerable' Avalanche Danger Is the Real Killer on Ski Trails

Think the scariest thing on a ski day is a double black diamond? Think again. The real killer isn't the steepest run or the iciest mogul field—it's the day the avalanche forecast says “Considerable.” That's the level that lures you into thinking you're safe enough to push a little further, and it's exactly where the statistics go dark. We're not talking about the backcountry either; this mindset bleeds into how we ski inbounds trails, where the blue squares and black diamonds feel like a controlled playground. But the danger doesn't care about the trail rating. It cares about snowpack, slope angle, and human decision-making.

Here's the question we need to answer: Why does “Considerable” avalanche danger kill more skiers than “Extreme,” and what does that mean for how you should ski a resort trail?

The Misleading Ladder of Danger

The North American Public Avalanche Danger Scale has five levels: Low, Moderate, Considerable, High, and Extreme (avalanche.org). Most people read that as a linear progression—each step a little worse than the last. But the scale isn't linear; avalanche danger increases exponentially between levels, not linearly (avalanche.org). That means the jump from Moderate to Considerable is actually a bigger leap in risk than the jump from Low to Moderate. And the jump from Considerable to High? Even bigger.

So why does Considerable feel so benign? Because at Moderate, you're told to be cautious on steep slopes. At Considerable, the forecast still says “natural avalanches are possible” and “human-triggered avalanches are likely” (avalanche.org). That phrasing—possible versus likely—sounds like a small shift, but it's a psychological trap. We hear “likely” and think, “Well, it's not certain, so I can manage it.” But “likely” means that on a slope with the right aspect and angle, your skis could be the straw that breaks the snowpack's back.

And here's the kicker: this scale isn't just for the backcountry. It's a mental model that should inform every run you take, even inbounds. Because the snowpack doesn't care if you're inside a rope line. It cares about the terrain.

What the Numbers Actually Say

Let's look at the fatality data. U.S. avalanche fatalities have stayed remarkably stable since 1995, at about 25 to 30 per year, despite an 8-fold increase in backcountry use (avalanche.org). That's not because we've gotten safer; it's because the danger is concentrated in specific conditions. And those conditions almost always involve moderate-to-considerable danger ratings, not extreme ones. At Extreme, the advice is simple: avoid all avalanche terrain (avalanche.org). So people do. At High, travel in avalanche terrain is not recommended (avalanche.org). So most people, even the cocky ones, back off. But at Considerable, the message is muddier: “human-triggered avalanches are likely” but not guaranteed. That ambiguity is deadly.

Now, layer in the resort context. In the 2024/25 season, NSAA reported 50 skier and snowboarder fatalities at U.S. ski areas—a rate of less than one per million visits (nsaa.org). But the leading cause wasn't avalanches; it was collisions with trees, accounting for nearly half of those deaths (nsaa.org). That's inbounds, where the avalanche danger is supposedly managed by ski patrol. Yet the same mindset that leads people to ski too fast on a blue square is the mindset that leads them to ski into a tree well or trigger a slide in an unmarked gully.

Here's the uncomfortable truth: the trail rating system—green circle, blue square, black diamond—is relative to each resort, not standardized nationally (nsaa.org). A blue square at one resort might be a black diamond at another. So when you're skiing a blue square, you have no idea what the actual gradient is. But you do know the avalanche danger. And that's the number that should dictate your speed, your line, and your risk tolerance.

Technique Isn't the Problem—Decision-Making Is

We love to blame technique. We think if we just carve better, we'll be safer. But the data says otherwise. Most catastrophic incidents in the 2024/25 season involved male skiers on more difficult (intermediate) terrain, with speed, loss of control, and collisions with trees as the primary factors (nsaa.org). That's not a technique problem; that's a judgment problem. The skier chose a run that was beyond their ability, or skied too fast for the conditions, or didn't account for the snowpack.

And here's where avalanche danger intersects with technique. When you're skiing inbounds, you're usually on groomed runs, which are less likely to slide. But the moment you duck under a rope or ski off-piste within the resort boundary, you're in avalanche terrain. The danger rating for the day applies to those slopes. And at Considerable, the likelihood of triggering a slide is high enough that even expert skiers—with perfect technique—can be caught.

So what does good technique actually buy you? It buys you the ability to react, to stop, to avoid a tree. But it doesn't buy you immunity from a slab avalanche. That's a decision you make before you drop in.

How to Actually Use the Forecast

Here's a concrete example. Say you're at a resort in Colorado, and the avalanche forecast is Considerable for the alpine and treeline elevations, but Moderate below treeline (avalanche.org). You're an intermediate skier, comfortable on blue squares. You see a tempting glade off the side of a blue run, with fresh powder and no tracks. Your technique is decent—you can make short turns, you can stop on a dime. But the snowpack is unstable. At Considerable, human-triggered avalanches are likely. That glade, even if it's within the resort boundary, is not worth the risk.

So what do we do? We check the forecast before we ski, and we adjust our terrain choices accordingly. Parks Canada strongly recommends that the general public avoid areas where the danger is HIGH or EXTREME, and limit travel to simple terrain or stay within ski resort boundaries (parks.canada.ca). But even at Considerable, we need to be more conservative than we think. The scale is exponential, so Considerable is not “a little worse” than Moderate—it's a significant step up in risk.

And here's the thing: the resort boundary doesn't guarantee safety. Ski patrol controls avalanches on the slopes they've assessed, but they can't control every tree well or every unpatrolled sidecountry. In 2024/25, snow immersion incidents, including tree wells, accounted for roughly ten percent of ski-area fatalities (nsaa.org). That's a real risk, and it's exacerbated by deep snow and poor visibility—conditions that often accompany Considerable danger days.

So my advice is simple: treat Considerable as a red flag. On those days, stick to groomed runs that are well within your ability, skip the trees, and dial back your speed. Your technique isn't going to save you from an avalanche; your decision-making will.

Quick tip: If the avalanche forecast is Considerable, ski with a partner, carry a beacon, shovel, and probe, and stay on slopes under 30 degrees. That's the angle where most avalanches release, and it's a number you can eyeball with practice.

What I'd Actually Do

If I'm skiing on a Considerable day, I'm not skiing anything steeper than a blue square, and I'm staying on groomed runs. I'm not ducking ropes, I'm not hiking to that secret powder stash, and I'm not letting my ego talk me into a black diamond just because I've skied it before. The snowpack doesn't care about my résumé. I'd also check the forecast for each elevation band, because the danger can vary dramatically (avalanche.org). And if the forecast is High or Extreme? I'm not even leaving the lodge. Parks Canada says to avoid avalanche terrain entirely at High and Extreme (parks.canada.ca), and I'm not going to argue with that.

Inbounds, I'd also pay attention to trail ratings, but I wouldn't trust them. A blue square at one resort might be a black diamond at another, so I'd ask the patroller or look at a slope map. But the avalanche forecast is the one number that's consistent across resorts, and it's the one that tells you the real story of the snowpack. So use it. It's the difference between a fun day and a fatal one.

Sources

• North American Public Avalanche Danger Scale - https://avalanche.org
• Avalanche danger scale (Parks Canada) - https://www.parks.canada.ca/pn-np/mtn/securiteenmontagne-mountainsafety/avalanche/echellerisque-dangerscale
• NSAA catastrophic injury fact sheet - https://nsaa.org/webdocs/Media_Public/IndustryStats/catastrophic_injury_fact_sheet_2025.pdf
• NSAA fatal incident fact sheet - https://nsaa.org/webdocs/Media_Public/IndustryStats/fatality_fact_sheet_2025.pdf
• NSAA ski trail ratings - https://nsaa.org