Turnagain Pass

The Easterly winds that were on the rise yesterday have continued their climb overnight and are expected to level off in the ‘strong’ category today – which means averages between 26-38mph. There is plenty of loose snow available for transport and yesterday evening slopes were being rapidly loaded. At least two natural avalanches were witnessed on the SW face of Sunburst during the rapid wind loading. One was caught on video, that plus additional details HERE.

Additionally, there was one very interesting avalanche on the SW face of Sunburst that occurred earlier in the day between 12:00 and 1:00pm. It is believed to have been a natural triggered by warming plus minor wind loading. This slide occurred early enough in the day that neither the sun nor the wind was in full effect. In my mind, this shows how close to the tipping point some of these slopes are.

Below is the believed natural from around noon on the SW face of Sunburst (3,700′ elevation).  The path just to the left of this slide (partially in view) released 4 hours later, around 5:00pm and is one of the two naturals mentioned earlier.

For today, steering clear of steep slopes with recent wind loading will be the key to avoiding this problem. South and West aspects will be the most likely candidates for loading, but due to terrain channeling and cross-loading, all aspects are suspect including rollovers. Not only is a simple wind slab concerning enough, the fact that weak faceted snow exists under these slabs makes them downright dangerous. This is because they have the potential to be 2-3′ deep and propagate across bowls.

On slopes that are not seeing wind loading there is still the potential for triggering a persistent slab avalanche. Even though it has been over a week since Turnagain Pass has seen measurable snowfall and five days for the Girdwood Valley, we are still seeing human triggered avalanches breaking in weak snow around 2′ deep. The most recent slides were from yesterday:

1- Snowmachine triggered slab while climbing a chute in 2nd Bowl
2- Snowboarder triggered slab while descending into 1st Bowl            *Both of these are in the Seattle Creek drainage and details are limited.

On Friday, we had two large persistent slab avalanches occur. These were:

1- Skier triggered by a group ascending the headwall that joins the Magnum and Cornbiscuit ridges  – see photo below with more photos HERE plus a write up by the party HERE (Many thanks to the party for sharing their experience!).
2- Snowboarder triggered slide in Warm-up Bowl in Seattle Creek. This avalanche was reported to have a crown depth of 1-5′, width of 300′ and running to lower angle terrain.

Image is of the avalanche triggered on the headwall between Magnum and Cornbiscuit (2/21/2014, NW facing and 3,500′ elev.)

Although time is helping to decrease the likelihood of triggering one of these avalanches, the possibility remains. Many folks have been able to ski, snowboard and ride steep terrain without a problem – this is the hard part and why these avalanches are a roll of the dice right now. At the end of the day, it comes down to personal risk threshold. If you choose to hit the steeps, safe travel practices will help to hedge your bets. If you do not want to deal with a potentially life changing avalanche, then recreating on slopes less than 35 degrees with nothing steeper above you is the ticket. 

Sun and warming:
Due to the wind, sunshine today will likely have a hard time warming the surface snow above treeline. This includes the sun crusts on southerly aspects left over from yesterday. However, if you do find a sheltered area with enough warming, persistent slab potential will increase along with sun induced point release avalanches. Keep an eye out for any south facing start zone that is seeing intense sun, little wind and dampening surface snow.