Turnagain Pass Avalanche Forecast

NW winds are forecasted to pick up today, blowing 15-25 mph with gusts into the 30s. There is light, soft snow available for transport. Watch for wind slabs building on leeward slopes. Avoid steep slopes that looked pillowed and pay attention to changing conditions. Wind flow from this direction can be stronger over Seattle Ridge. It also can be channeled through Turnagain Pass from the South and winds near Taylor Pass can be much stronger. Look for flagging (snow blowing off of ridges), surface snow getting stiffer, cracking and drifting. An observer yesterday triggered a small pocket of wind slab in steep, rocky terrain. There is more snow in Girdwood so expect slabs to be larger. Keep in mind; if winds are stronger than forecasted, natural avalanches may occur. 

Cornices grew during the storms last week. As always, give these features a wide berth and remember they can break further back than expected. A cornice fall at the high elevations could trigger a large avalanche on the slope below.

Snow available for transport today. 

We know the snowpack structure above 3000′ is poor, there is a dense hard slab (3-8+ feet thick) sitting on a variety of weak layers in the mid pack (including buried surface hoar) and old November facets near the ground. Deep persistent slab avalanches remain a concern in the advisory area. Triggering a deep slab is becoming more and more difficult, but is still possible. The most likely trigger spots are thin areas in the snow cover, often near rocks, or where the slope rolls over. High peaks, that see wind, can also be thinner and it is more likely to find the trigger point for a deep slab where some of the slab has been stripped away. 

Key points that keep in mind about our current snowpack:

• We have a ‘low probability, high consequence’ situation at the upper elevations for deep slab avalanches. If you do trigger an avalanche it could be huge and unsurvivable.
• Obvious signs of instability are not likely to been seen before a deep slab is triggered (such as whumpfing and cracking) 
• Remote triggering is possible
• There may already be tracks on the slope
• This issue can simply be avoided by sticking to terrain below 3000’ (which is a good portion of terrain at Turnagain) or choosing low-consequence terrain in the Alpine

Snowpack structure above 3000′ on Sunburst.

On slopes that are protected from the wind expect loose snow avalanches (sluffs) in steep terrain. The additional snow we picked up over the past couple days, 6-10″ in Girdwood and 3-5″ at Turnagain landed on already loose surface snow. The surface snow has been quick to sluff on steep slopes and the new snow just added to the volume of the sluffs. As the sluffs grow larger they could definitely catch a person by surprise, especially on steep, committing terrain.  Observers are reporting that the sluffs are running long distances and are large enough to have a powder cloud. Winds blowing today could initiate these off of the top of ridgelines.