Turnagain Pass

We have not observed or received any reports of natural avalanche activity with the exception of glide releases in the past two days.  The temperatures have been dipping below freezing every night but have been slowly climbing again over the past two days. Warmer temperatures and longer days with direct sunshine on slopes means that the melt-freeze cycle is slowly migrating to colder aspects (specifically W-NW). Today and tomorrow it will be important to pay close attention to how the warming is affecting the pack. We are in a melt-freeze cycle on Southerly (SE-S-SW) slopes – hard frozen crusts in the morning, which turn to unsupportable mushy and unstable snow by the afternoon/evening, the less of a freeze the greater the likelihood of wet avalanches. Choosing what aspect to travel on, paying attention to the time of day and how long the slope you are on has been exposed to direct sunlight are essential to staying out of trouble.  As colder aspects heat up remember cold snow, persistent weak layers and free water are a bad combination.  Watch for roller balls and natural wet loose avalanches indicating surface warming. Wet loose snow avalanches may also trigger deeper slabs.

 If heading out for a fun day in the sun keep these points in mind:

• Once the snowpack becomes so wet it is unsupportable and ‘punchy’ to skis, snowmachines or boots – it’s time to head to a cooler aspect. 
• The steeper the Southerly slope, the more it will warm and the more dangerous it will be.
• Buried weak layers in the pack can make a small avalanche or sluff become bigger by propagating across the slope and/or stepping down. 
• Wet avalanches are hard to escape if you get caught and a small slide can be deadly if it pushes you into a terrain trap. 
• Rocky areas that are absorbing more heat should be avoided.

Click HERE for a great dicussion from the forecasters at Avalanche Canada on managing spring avalanche conditions.

Magnum, Super Bowl and Cornbicuit from the heli. A good look at shaded versus solar aspects. Choosing aspect is crucial this time of year. Photo: Graham Predeger

Cornices: Cornices are large and likely hanging close to their tipping point due to warm temperatures. Direct sunshine, a person, or a group of people on top these could be enough to cause one to break. Cornice crevasses have also been noted (opening slots where the cornice is pulling away from the ridge but has not broken off. Give cornices a wide berth from above and limit exposure under them from below. 

Eddies south side looks similar to the glide carnage of last year. Several glide avalanches have released and existing cracks are opening each day.  Seattle Ridge is also littered with opening cracks as well as the south side of Tincan. There was a new glide release observed in Lynx Creek yesterday. We expect this trend to continue today and tomorrow. Keep an eye out for glide cracks and limit time underneath them. Remember they are the entire snowpack releasing to the ground without warning. 

Eddies RWIS camera capturing a glide release just after 7 pm last night

Eddies glide avalanches. Photo: Jessie Haffener & Sam Galoob

Tincan glide cracks. Photo: Jessie Haffener & Sam Galoob

In this springtime transition it is important to remember on the shaded and cooler side of the mountains, Northerly aspects, a cold mostly dry snowpack exists. Afternoon warming may also influence how easy it is to trigger weak layers that are buried anywhere from 2-5′ below the surface. As folks venture out looking for “cold, soft snow” this remains a concern. Shaded aspects in the mid and upper elevations that haven’t avalanched already are the most suspect places for triggering a deeper slab.  On Monday the 4th skier on a slope in Triangle Bowl triggered a slab that ran on the April Fool’s storm rain crust. As the solar effect creeps onto more northerly slopes the interaction between cold snow and melt water also become more of a concern. 

This problem is one of low probability but high consequence as these are potentially large and unsurvivable slides.

Keep these points in mind:  

• It will take someone hitting a ‘thin spot’ in the slab, or a large trigger such as a snowmachine and/or groups of people or a cornice fall.. 
• There may be no signs of instability before the slope shatters 
• Several tracks may be on a slope before it releases
• Stability tests may not produce any notable results