Turnagain Pass

Friday there were two large snowmachine triggered avalanches in our advisory area. One in Seattle Creek where a rider was completely buried except for his hand sticking out.  He was quickly rescued by his party but his sled was not located. In Lynx Creek a snowmachiner triggered a slope just after he crested the hill but was not caught. One of his partners commented, “If I had tried high-marking at the same time as him or right after him I would not have made it outta there.” No obvious signs of instability were observed and in both cases there was already tracks on the slope. 

Both of these avalanches were triggered on an old/weak foundation, facets near the ground. This upside down structure exists in many places across our forecast zone, but not everywhere. Due to the spacial variability of our current snowpack assessing the snow that is across an entire slope is difficult and near impossible. Many folks have been able to snowmachine or ski/ride on a variety of steep terrain without incident over the last few days. This speaks to the uncertainty of our current avalanche problem and the dangers of a stabilizing snowpack. The likelihood of triggering a deep persistent slab is decreasing, but the consiquences remain high should you find the wrong spot. The slab in Seattle Creek was reported to be 4-6′ deep and the avalanche in Lynx 1-3′ deep. This type of avalanche is often triggered in a thin part of the slab, near rocks or on the edge of the slab. These can also be triggered by multiple skiers/boarders and/or snowmachines on, near or under slopes. Remember just because the slope has lots of tracks does not mean the slope is safe. It may be the 3rd or 10th or 25th track that tips the balance. Above freezing temperatures in the Alpine and direct sunshine may also make these slabs easier to initiate.  This is a lot to factor into decision making this weekend, but please keep the following in mind: 

1. An avalanche on a large open slope may propagate and run further than expected.
2. Obvious signs like shooting cracks or collapsing “whumpfing” are unlikely today.
3. Identify safe zones and travel one at a time between islands of safety.
4. Make a plan and reasses with your partners as you travel. Radios can be very helpful.
5. Be aware of other groups and if an area becomes too crowded it may not be possible to practice safe travel protocol. Consider going elsewhere. 

Seattle Creek Avalanche that occured on Friday, Feb.3 near the -3 bowl on a NE aspect. Photo courtesy of Brad Larson

This crown in Lynx Creek wraps around the ridge on a Northeast facing slope. Notice the vegitation and places where the ground is exposed. Photo by Mahear Aboueid

The crown of the Lynx Creek avalanche can be seen easily from the Johnson Pass trail head and shows the bigger view of the crown as it wraps around the slope. 

In addition to deep persistent slab avalanches there are a few other avalanche concerns to pay attention to today. The sun is out and affecting the snow in terrain on the Southern half of the compass. Warm temperatures and direct sunlight may also play a factor in all of these concerns. Pay attention to changing conditions!

Wind Slabs: Old stubborn wind slabs as well as some newer ones may be triggered on leeward slopes. Look out for pillowed or drifted snow, listened for hollow sounds and avoid areas with stiff snow over soft snow. Warming temperatures and direct sunlight may make these slabs easier to trigger on solar aspects.

Loose snow: With 4-8″ of loose snow on the surface over a dense base, watch your sluffs and watch how the sun is affecting the snow around you. These may pack enough punch to push you somewhere you don’t want to go i.e. a terrain trap. 

Cornices: Yesterday large cracks were reported along the some of the cornices in the back bowls of Seattle Ridge. Cornces are unpredictable hazards and can break farther back onto a ridge than expected and have the potential to trigger an avalanche on the slope below. Give ridge lines extra space – they may have a cornice on the other side. 

Sun triggered roller balls were observed on many South and East facing slopes.