Turnagain Pass

Roughly 1-3 feet of snow is covering a widespread layer of buried surface hoar across our region. In many places this snow is too loose to form a slab and the surface snow ’sluffs’ away with the weight of a person. In some areas of the alpine this week, where winds have created a denser more cohesive slab, the buried surface hoar has been reactive to both skiers and snowmachiners. Yesterday a group on Eddies triggered a slab remotely from the ridge above the steep Southwest face. This slab was 2 feet deep by 80 feet wide and ran to valley bottom. In general these slabs have been small in size, but large enough to take someone for an undesirable ride over rocks or possibly bury a person in a terrain trap. With that said a lot of people have been riding and skiing in steep terrain without incident where winds didn’t affect the snow or form a slab. In the periphery areas of Girdwood to Placer Valley where more sustained winds affected this zone, slabs may be larger and more connected. Basically this problem requires the ability to assess the snow and terrain as you venture into the mountains with an understanding that triggering even a small soft or hard slab could have consequences in the wrong place. Identify terrain traps like gullies, cliffs or rocks below before committing to a steep slope.  

Snowmachine triggered avalanche in God’s Country near Pyramid on a SE aspect that was triggered remotely on Sunday.

 Natural slab avalanche on Wolverine’s South face that occurred near the end of the storm last Friday. This is a good example of the potential size of a persistent slab and the kind of steep wind loaded terrain it could found in.

Hand pit on Sunburst at 3300′ on West aspect revealed the very large and well preserved buried surface hoar that is suspect in places with a consolidated slab. 

Expect loose dry snow to be fast moving in steep terrain and entrain more snow as it picks up speed. This quick moving surface snow can knock a person off their feet. Be aware of the consequences below you and manage your ‘sluff’ by slowing down and letting it pass you. 

Sluffing around ski tracks on SW face of Sunburst

Two and a half weeks have passed since a storm delivered heavy rain and strong wind to our region and caused a natural deep slab avalanche to release on the Southwest face of Sunburst. Immediately following this event the snowpack stabilized below 3000’ due to wet snow freezing into a solid strong layer. Observations over the last few weeks have found poor structure  (basal facets) near the ground in targeted thinner areas of the snowpack above 3000’. This leaves us with some degree of uncertainty in the upper most reaches of our forecast zone. Triggering a deep slab avalanche is becoming more unlikely with time, but is not impossible on a large steep slope combined with thin trigger spots to initiate such an avalanche. Should you find yourself approaching a 4000’ peak, remember this is a hard to trigger, low likelihood problem that deserves acknowledgment of it’s potential.