Turnagain Pass

Timing is everything…

It’s that time of year where clear skies freeze up the snow surface at night and then the sun and warm air temperatures turn hard crusts into slop later in the day.  A MODERATE danger in the morning transitions to a CONSIDERABLE or even HIGH danger in the afternoon and into the evening hours. Choosing what aspect to travel on, paying attention to the time of day and how long the slope you are playing on has been exposed to direct sunlight are essential to staying out of trouble. Remember to avoid the runout areas of Southerly slopes as well as things heat up. 

Yesterday observers saw natural wet avalanche activity start around 12:30 pm and continue into the evening on Southerly slopes. Natural avalanches were witnessed on Seattle Ridge, in Girdwood, in Placer and in Whittier. A large skier triggered avalanche occurred on Sunburst on Thursday on a Southerly slope. This stepped down to the ground. Wet activity has been observed all week on Southerly slopes and zones with thin snowpacks have been particularly active where free water is interacting with old weak snow. Wet loose snow avalanches may also trigger deeper slabs.   

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

• 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 (due to more warming but also because it’s simply steeper).
• Buried weak layers in the pack can make a small avalanche or sluff become bigger by propagating across the slope and/or stepping down. 

All of the avalanches in the pictures below are large enough to injure, bury or kill a person. Extra caution is advised. Natural avalanches are happening. Get Out of Harm’s Way! 

Sunburst avalanche that was triggered around 4:30 pm on Thursday afternoon.

Natural avalanche on Seattle that was witnessed around 4 pm yesterday. Avalanche path in center of photo that has dirty debris. 

Natural that occured yesterday around 5:30 pm on Ragged Top mountain in Girdwood.

Wet loose that triggered wet slabs and ran to the ground on Corbiscuit. Photo: APU Snow Science Class

On the shaded and cool side of the mountains (Northerly aspects) dry snow still exists. While wet snow issues are not a problem here, deep slab issues are. There are several weak layers anywhere from 2-5′ below the surface. The most notable is the March 27 buried surface hoar and/or facets; these layers were buried by 3-6′ of snow during the 10-day April Fools storm.  As folks venture out looking for “cold snow” this remains a concern. Shaded aspects (NE – NW – W) in the mid and upper elevations that haven’t avalanched already are the most suspect places for triggering a deep slab. 

This problem is one of low probability but high consequence as these are large and potentially unsurvivable slides. As the snowpack continues to adjust, triggering will become more stubborn and less likely with time. Keep these point 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.
• These slides can be triggered remotely, for example, from a ridge or bench on the top/side or below. 
• 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

Small glide avalanches have released on Southeast facing Seattle Ridge the past couple days. On Wednesday a larger glide released on the South aspect of Eddies ridge. We expect this trend to continue with the warm days ahead. Keep an eye out for glide cracks, full depth cracks in the snow, and limit time underneath them. Most cracks appear to be small and in areas less traveled, but a glide avalanche can also release with little warning when a crack is not visible prior. 

Cornices: Cornices are large and likely hanging close to their tipping point as the warming trend continues. Direct sunshine, a person, or a group of people on top these could be enough to cause one to break. An observer in Seattle Creek noted large cornice cracks/crevasses along some of the ridgelines. Give cornices a wide berth from above and limit exposure under them from below. 

Glide avalanches and glide cracks near the Seattle Ridge uptrack.