On the first day of a glacial ski traverse I did recently in Alaska’s Chugach Range, I forgot to turn on my avalanche beacon.

I should have known better. Last March, I took the National Ski Patrol’s (NSP) Level I Avalanche course at AMC’s Joe Dodge Lodge in Pinkham Notch. Taught by NSP-certified instructors who are also members of the Mount Washington Volunteer Ski Patrol, the two-day course focused on avalanche terrain recognition, avoidance, and preparation.

Les Blomberg, lead NSP instructor for this season’s now three-day program, wasn’t surprised by my gaffe.

“The class is the beginning,” he says. “It will allow you to identify when you’re in danger, but there’s this whole stream of behaviors that have to become second nature.”

Making sure my beacon was on did become a ritual, but I witnessed enough point slides on nearby slopes to drive home the main message of the NSP course—know how to avoid avalanche terrain before you’re in it.

KNOW BEFORE YOU GO Ninety-five percent of avalanche accidents in the U.S. are caused by the victim or someone within his or her party, which makes education essential to preventing injuries and fatalities. Part of that education, Blomberg says, begins at home, miles from the trail or terrain in question.

Check the weather conditions—past, current, and future. Temperature changes, snowfall, and wind direction and duration all affect the stability of the snowpack. Tuckerman Ravine, for example, is on the leeward (facing away from the wind) side of Mount Washington and therefore sees significant accumulation from winds driving snow into the glacial bowl.

The right combination of weather factors can create slab avalanche conditions, where a weaker layer of snow sandwiched between more cohesive layers may fail, triggering a tsunami of white stuff that can leave behind a wide path of destruction. This is often the deadliest type of avalanche for backcountry travelers.

In the White Mountains, expert avalanche forecasting is done for us in some of the high-risk areas. Forest Service Snow Rangers, using the U.S. Avalanche Danger Scale, measure snow conditions in Huntington and Tuckerman ravines on Mount Washington every day and post their findings on AMC's website and AMC’s Pinkham Notch Visitor Center. If the risk is expected to be great, Blomberg advises, “You can always go climbing and skiing another day.”

THE LAY OF THE LAND “If the rangers are telling you there’s moderate conditions, one of the first questions you have to ask is, ‘Do I have the knowledge to be able to assess the snow I’m on?’” Blomberg says. “Most people do not.” Moderate conditions indicate that human-triggered slides are possible and can exist in areas not patrolled by snow rangers.

If you’re in the backcountry, there are some general rules of thumb. According to the book used in the NSP course, Snow Sense: A Guide to Evaluating Snow Avalanche Hazard, most slab avalanches will occur on slopes with angles between 25 and 60 degrees. Snow generally sluffs off slopes steeper than 60 degrees, but the majority of slab avalanches occur between 35 and 40 degrees. Measuring slope angle can be a quick and easy habit with an inclinometer, a device built into many compasses or available as an inexpensive, pocket-sized version.

Slope aspect—which direction a slope faces in relation to wind and sun—is a secondary visual cue. Ridges or slopes that are leeward are often snow-loaded by wind. So too are the snow cornices that form and jut out over some leeward ridges and gullies. And slopes that remain in the shadows are often less stable than those where the snowpack bonds under the sun’s warmth.

IF IN DOUBT, KEEP OUT To travel safely near avalanche terrain, a basic understanding of snowpack layering and bonding is critical, and this comes first with education and then with many seasons of experience. If you stick a ski pole in the snow or hop on the surface of a 35-degree slope, can you interpret how the snow responds? If not, Blomberg’s advice is simple: “If you don’t know how to assess avalanche stability, then you had better back off.”