Turnagain Pass Avalanche Forecast

A large avalanche was remotely triggered by a helicopter landing at a pick-up spot in Winner Creek near Girdwood yesterday. This avalanche occured at 2500′ and released on the layer of weak faceted snow on a slick crust that has been the culprit in most of the avalanches over the past week. It was triggered from 1/4 of a mile away, wrapped 750′ around a ridge releasing on multiple aspects and the crown was 3-6′ deep. The pick-up spot had been used 10 times the day before. Why did it go the 11th time? The likelihood of natural avalanches has decreased as winds have hammered many areas and stripped away all the soft snow but a skier or snowmachiner triggering an deep slab avalanche remains a very real and scary possibility. Knowing where in the terrain that avalanche could be triggered and what it will take to trigger it is the hard part. This is the unfortunate reality of this type of avalanche problem. With a deep slab problem it is important to remember no signs of instability may be present before a slope releases. It may be the 10th person onto the slope that finds the trigger point and slopes may be triggered remotely. It is crucial to visualize the consequences if the slope does slide. Are there terrain traps below?  Bigger slope = Bigger avalanche. Thin spots near rocks and along ridgelines are likely areas to find the trigger point. Widespread buried surface hoar and facets have been well documented at all elevations under a thick, connected slab and finding the wrong spot could be deadly.  

Crown in Winner Creek, avalanche wrapped around the ridge to the north.

Arrows point to crowns on both sides of the ridge

Snowpack structure on Tincan. Weak snow under a hard slab

The Northwest winds continued for a second day yesterday blowing 25-35 mph and gusting into the 60s on Seattle Ridge. Winds are forecast to remain elevated today into tonight and then mellow out by tomorrow. Most of the soft snow is now either blown into the atmosphere or been pounded into hard slabs and sastrugi. However, while traveling along ridgelines, be aware of the potential for wind slabs on a variety of aspects due to unusual wind loading patterns and cross loading. Smooth supportable surfaces where the snow is hollow sounding are suspect, especially if the slope is unsupported. Look for cracking and identify terrain features with a pillow-shaped look where triggering a wind slab could break above you. A wind slab could step down to older snow in the snowpack and create a much deeper and more dangerous avalanche.

Seattle Ridge has been getting top-loaded by this wind direction. 

Cornices are large and looming and wind loading can add stress. Give these an extra wide berth and limit exposure underneath them.  A cornice fall could trigger an avalanche on a slope below.