Turnagain Pass Avalanche Forecast

Above ~2,000′ our concern is the New Year’s storm snow that has now settled into a slab, around 12 – 20″ at Turnagain Pass and 20-30″ in the Girdwood Valley.  We have the buried surface hoar that was the cause for last week’s avalanche activity that sits right under this New Year’s snow. Could this slab/weak layer combination be triggered by the weight of a skier or snowmachiner? The answer is still YES. The buried surface hoar layer is slowly gaining strength and the slab is becoming more stubborn to trigger. However, snow pit results are still showing this layer to be reactive and to propagate – meaning human triggered slabs are possible if one hits the wrong spot on the slope. In addition, we are also concerned about slopes that avalanched in early December which have a thinner snowpack and harbor facets under the slab. Observers yesterday dug in a thinner spot on Sunburst and found reactive facets near the ground. 

On January 2nd it rained up to 2,000-2,300′, creating melt-freeze crusts in the upper snowpack at these elevations and below, making triggering an avalanche unlikely in lower elevation terrain.

For those riders and skiers headed out today:

• Keep in mind that travel in the upper elevations is where triggering a slab is most likely. This is above 2,000′ where NO crusts exist in the top foot of the snowpack.
• Remotely triggering a slab is possible, several tracks may be on the slope before a slab releases and no signs saying ‘the slope is unstable’ are likely to be present.
• Larger slopes are more suspect as well and those with rocky features.
• Safe travel habits are always key, but especially when dealing with persistent and deep persistent slab avalanche problems: expose only one person at a time, have an escape route planned, watch your buddies closely and view all slopes as avalanche paths. If the snow does slide where will it go? Avoid terrain traps. 

 Wendy’s video and photo from 3,000′ on Sunday illustrate our current buried surface hoar issue well: 

Thin snowpack at 3400′ on Sunburst. Note the weak faceted snow at the base under the slab. Photo: Sam Galoob

Still reading… Deep Persistent Slabs have been in the forecast every day starting December 14th. Unfortunately it is a concern that we can’t ignore. At high elevations above 3,000’, human triggered large and dangerous deep slab avalanches are still possible. Weak sugary snow (basal facets) near the ground is creating a low probability/high consequence avalanche problem that is impossible to outsmart and will take a long time to heal. A big trigger like a snowmachine, more than one skier on the slope at the same time or a slab avalanche in the upper layers of the snowpack may be enough force to initiate a deep slab avalanche. Likely trigger spots will be in thinner areas of the snowpack that are connected to large, loaded slopes. Cautious route-finding is essential. This includes thinking about the remote trigger potential from below.