Race conditions
& safety

The Susitna 100 and Little Su 50K run the same trail on the same weekend, so conditions are much the same for both. This page covers what the winter can throw at you and how to handle it.
Read this before race day, not on the trail.

Weather:
Expect Anything

Plan for a temperature range from 40°F above zero to 40°F below. In practice you usually land somewhere reasonable between those extremes, but pack for the range, not the forecast.

These are wilderness races, subject to Mother Nature's whims. Each year's conditions are set as much by the weather two weeks out as by the whole preceding winter. The course sits between two forces: the Alaska Range, which sends an "arctic express" of cold north wind and clear skies that'll freeze exposed skin in minutes, and Knik Arm, which brings warmer but wet storms that can dump a foot of fresh snow.

Start tracking Big Lake / Willow weather the Monday before the race. Temperature drives your clothing and pacing decisions more than anything else.

Daylight is the predictable part. Mid-February gives Anchorage about nine hours of daylight, but the far-north twilight stretches that. Expect slow dawns and dusks that add a few hours of muted light you navigate without a headlamp.

The trail is built by snowmachine traffic, and conditions shift fast. You may hit:

Trail Conditions

Fresh snow

Even 6 inches unconsolidated slows everyone, especially bikers and runners. Wake up to fresh snow? You can declare into the ski or foot division race morning for an easier (still hard) day.

thaw then freeze

The trail turns to a skating rink. This is the one condition that's genuinely rough on skiers and snowshoers. Pro tip: declare for foot and put short sheet-metal screws in your shoes.

Thaws

Mid-winter Chinooks can push above freezing and soften the trail into a slush bog. The trail absorbs a few days of thaw before it's impassable, but wet feet and gear become a constant problem.

Cold, dry snow

Extended cold (below 0°F for a week+) dries snow to the consistency of beach sand. Bikers walk, runners reach for snowshoes.

This is the hazard most likely to end your race badly.

Several rivers on the course are prone to overflow. That is unfrozen water forced up over the top of the ice, caused by heavy snow, rain, or mid-winter thaw. It can happen regardless of the weather.

Getting wet in sub-freezing temperatures is life threatening. Wet feet plus prolonged cold is a direct path to frostbite. Keep your feet dry at all costs! That could mean going an extra couple of miles around the overflow.

If you hit overflow:

  • Stop and read it. Check how far it extends and how thick the ice is beneath the water.

  • It may be possible to step across carefully or move through fast.

  • Carry a couple of heavy duty trash bags you can pull over your feet and legs like waders to cross shallow overflow dry.

River Crossings
& Overflow

The course is a chain of common snowmachine and dog sled trails linked together. Here are four things to keep you on track:

1. The course description

Study the Course pages and the distances between checkpoints — bring a copy. Get a feel for your pace so you can estimate times between checkpoints. Be realistic: you'll slow down, and surface conditions can push you off your estimate by 30–60 minutes.

2. Trail Markers

~1,000 lath stakes, hand-labeled "SU 100" on both sides, with reflective tape that lights up under a headlamp.If you go more than 15 or 30 minutes without seeing a marker, take action. Other groups mark their own trails out here, so be sure to follow only the SU 100 or LS 50K markers.

3. Checkpoint Controls

You check in and out at every checkpoint; it's how the race tracks you. If you are overdue at a checkpoint and a search may launch. Patrols run each segment on snowmachines and will stop to check your condition.

Navigation:
Staying Found

They travel together. As an endurance racer you probably know dehydration; hypothermia is the cold country bonus danger.

Preventing both:

  • Drink early and often; at least a pint an hour. Checkpoints average ~16 miles apart, so you shouldn't be over-burdened with water weight.

  • Don't overdress. Balance clothing against temperature and wind, but avoid overheating — the sweat you generate soaks your layers and chills you through dehydration. You stay warm on movement, water, and minimal clothing more than on bulk.

Treating it, if it sets in:

  1. If you are feeling cold, dizzy, or losing motor control, start drinking fluids and eating carbohydrates immediately.

  2. Out of water? If you're carrying a stove, heat a pint. It takes under ten minutes.

  3. Change into dry clothes. Wet clothing bleeds your body heat warming the sweat in it. Go heavy on the extremities. They say "if your feet are cold, put on a hat."

  4. Keep moving if you can as it's the best way to generate heat. Out of your bindings/pedals and jog 5–10 minutes to push blood into your toes.

  5. If you can't move, get into your sleeping bag and bivy, warm water and calories, rest. Your temperature should rebound. If you've reached this point, consider flagging a patrol for evacuation.

Hypothermia
& Dehydration

Frostbite rides along with hypothermia and dehydration, so everything above helps prevent it. However, it also creeps in two other ways:

1. Wind exposure

Even warm and well-hydrated, exposed skin in a brisk north or west wind is at risk. The nose is the classic casualty. Fighting a headwind? A face mask or strips of duct tape across the nose windproof your face.

2. Localized heat loss

As your torso cools, your body pulls warm blood away from fingers and toes to protect your core. Get those wet and it gets ugly fast. Fingers are easy — pull on your extreme mittens. Cold feet — dry socks and another layer, or a neoprene outer boot.

If you get frostbite or think you might: get to the nearest checkpoint, ahead or behind. Flag a snowmachine if you can.

Frostbite