Turnagain Pass

Triggering an deep slab avalanche 2-4+ feet thick remains a scary possibility. Strong Northwest winds that ended Thursday morning loaded a variety of aspects and scoured many ridge lines.  Shaded aspects (North to Northeast) may be more loaded with this unusual wind direction. All aspects are suspect due to well preserved and widespread buried surface hoar and facets under a thick, connected slab 2-4+ feet thick. A thin sun crust on solar aspects may soften in the afternoon with the sun and remember daily warming in the mid 30F’s can make it easier to trigger a slab. Our current hard-pack snow conditions are deceiving and may give the appearance of ‘stable snow’. Knowing where in the terrain a large and destructive avalanche could be triggered is a difficult question. It may be the 10th person onto the slope that finds a thin part of the snowpack (a trigger point) or it could be a person triggering a slab remotely on an adjacent slope or below. This was the case on Tuesday in Girdwood when a helicopter remotely triggered an avalanche from 1/4 mile away. There is a lot of uncertainty around this avalanche problem and just how stubborn it will be to trigger now that winds have mellowed out. 

With a deep slab problem it is important to remember no signs of instability may be present before a slope releases.  Thin spots near rocks and along ridgelines are likely trigger points. Take a moment to visualize the consequences if the slope does slide. How far would a very large avalanche run in this terrain? Are there terrain traps below?   

Natural avalanche on a NE aspect of Raggedtop was first noticed Tuesday morning and is a good example of the size and distance a very large avalanche could run. 

An avalanche triggered Tuesday in Girdwood near Notch Mountain at 2500′. This slab was 3-6′ deep and failed on facets on top of a slick crust, bed surface. 

Wind Slabs: Wind slabs have formed on a variety of aspects due to unusual loading patterns and cross loading from strong Northwest winds this week. 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. Warming from the sun can make triggering easier in the afternoon, and a wind slab could step down to older snow and create a much deeper and more dangerous avalanche.

Cornices: Cornices are large and looming and the sun and above freezing temperatures can make them more unstable. Give cornices lots of space and limit exposure underneath them.  

Northern aspect of Magnum with recent wind loading from several days of strong NW winds. In Turnagain Pass this wind direction can funnel through some terrain from the South and load Northern aspects.