Turnagain Pass

With sustained winds averaging in the mid-50’s mph on Sunday (and gusts to 101mph on Sunburst)  2-4′ thick wind slabs are possible on steep leeward slopes, particularly above treeline; though it is worth recognizing that strong winds such as these have a tendency to load slopes far below ridgelines, creating a mid-slope avalanche problem. There was significant cross-loading as well. Identifiying where the winds deposited the snow is crucial. Look for pillowed snow, listen for hollow sounds and pay attention to stiff snow under your skis, snowboards or snowmachines. Watch for shooting cracks and remember even a small pocket of wind slab in steep terrain can have high consequences. Wind slabs are notorious for letting you travel out onto them and then breaking above you. Evalute carefully before commiting to steep terrain from above or below.

Sustained winds, relatively warm temps and moist snow have continued to grow large cornices.  These have the potential to fall naturally or be triggered by the weight of a person or machine and can be very dangerous. Travel under or on them should be avoided. They have the tendency to break farther back from the ridge than expected and can trigger an avalanche on the slope below by adding a lot of weight quickly. As you approach ridgelines and the entrances to backcountry bowls make sure you aren’t accidently traveling on overhanging snow. 

In some parts of the advisory area now sitting under 5-7′ of settled storm snow is a layer of old faceted snow on top of the Thanksgiving Rain Crust. This still needs to be a consideration as you travel into the backcountry today. This is a low probability, very high consequence set-up.  It is important to use safe travel practices and do not overload slopes with multiple skiers, boarders or snowmachines. Limiting your exposure time spent underneath large paths such as those that effect areas like Johnson Pass and the Lynx Creek drainage.  In addition we have limited snowpack information from Johnson Pass and Lynx Creek but we know that the snowpack is shallower. The surface hoar that developed prior to Christmas may be buried and preserved especially near the creek. Watch for signs of instability: recent avalanches, shooting cracks, collapsing and whumpfing. Pay attention to snow depth and trigger points. Deep slabs are most easily triggered from shallow spots where the weight of the traveler can more easily effect the weak layer. 

NOTE:  In areas such as Summit Lake, the snowpack is shallower and harbors more weak layers under the recent storm snow.  See Wendy’s observation and write-up from a snowboarder-triggered avalanche (Saturday) that failed on a buried surface hoar layer that ran on a mellow (28-30 degree) slope.