When you reach Fred he’s sitting in the snow groaning, mostly about the demise of his ski season, but also because he’s hurting. Your group is all tired after skiing all day. It’s mid-January and it’s getting dark. Snow is starting to fall.

What do you do?

First: keep Fred warm. Injured victims are more susceptible to hypothermia. Seat him on a backpack, off the snow and get all his layers on. Synch his hat, zipper his jackets, get him into puffy pants and double up his puffy jackets.

Second: ‘smoke a cigarette’, as Paul Petzoldt, founder of NOLS, once said. In the excitement of emergencies it is important to think, then act. A virtual cigarette allows thinking time. A deep breath and chilling for several minutes saves hours in the long run, or may prevent another accident.

Third: develop a plan. Shelley, the most first aid savvy in the group, does a patient assessment exam. She determines Fred’s busted ankle is the only injury, but it’s unstable – meaning he can’t walk out. He’ll need to be hauled out. You, Fred and Shelley opt for self-rescue, rather than a cumbersome SAR mission. Shelley will ski to the road and grab a sled that happens to be in the back of your truck. She’ll also gather several recruits from nearby Diamond Peaks parking lot to haul the Fred-loaded sled back out. Your duty is to keep Fred warm until the recruits arrive.

Shelley splints Fred’s ankle and hits the trail. You start an emergency shelter.

Emergency shelters – different than a planned backcountry shelter – are built under time constraints (such as looming hypothermia) and without overnight gear (sleeping pad, sleeping bag or tent). The point of an emergency shelter is that shelter overhead reduces heat loss from convection (wind) and radiation to cold air, especially to clear skies.

The fastest emergency shelter is a trench bivy. To build a trench bivy, scribe a three- by six-foot rectangle in the snow. Dig down chest deep within that opening, widening as you go, making a room the shape of a bowl and the size of a three-person tent. For a roof, lay two sets of skis, bindings down, over the rectangle opening. Layer slabs of snow across the skis for a roof. Better yet, cover the skis with a guide tarp and then coat the tarp with six inches of snow. The result is a blizzard-proof shelter. Dig a small entrance, the size of your backpack, at one end. Building a trench bivy takes less than 30 minutes. The major drawback of a trench bivy is that your skis are committed to the shelter.

Tarps are essential survival gear in the winter backcountry, equal in importance to first aid kits. No piece of gear adds more warmth than a tarp. At the bare minimum bring a Space Emergency Blanket or the equivalent, such as the Emergency Blanket by MPI or the Adventure Medical Kits Heatsheet Blanket. Weighing just three ounces, these are ultra-light insurance. Space blankets are slippery though, and don’t work well for trench bivies.

The best emergency tarp is a ten- by eight-foot guide tarp with grommets on the corners and Velcro along the edges for converting into a bivy bag. Popular models include the Ultralite Guide Tarp by Brooks Range or the Integral Designs Guides Siltarp2.

For emergencies, in addition to a tarp, always bring an extra layer of clothing, such as a puffy jacket and pants. And in your first aid kit, the second most important item, after Benadryl, is the roll of athletic tape – perfect for splinting Fred’s ankle.

When packing, remember the disaster motto: It’s all good until it isn’t. So kick down for a good tarp.