Turnagain Pass

Overnight Easterly winds increased into the 20’s with gusts in the 30-40’s mph and moderate winds are expected to continue today. With 6-10” of low-density surface snow available for transport, isolated winds slabs are possible on leeward features. These slabs are expected to be small (4-8” thick), but if triggered in steep terrain, could send you for an unintentional ride.

Older winds slabs from the holiday storm event may still be lingering in very steep terrain, but otherwise this problem is becoming less likely as we move away from the storm. Yesterday a generally stable snowpack was observed where older wind affected snow was stabilizing quickly.

Ease into steep terrain today and pay attention for hard hollow sounding snow and shooting cracks. If you see snow being transported off of ridges be very aware of the consequences below you. 

Today’s secondary concern is Cornice Fall and Glide Cracks!

Very large cornice features have formed throughout the region as a result of a two-week storm that deposited ~9’ of snow and was accompanied by very high winds. Cornices 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. 

Glide cracks are appearing throughout the forecast region (Girdwood to Turnagain Pass.) These cracks appear to be opening fast and are very unpredictable. Similar to managing a cornice, it is best to avoid traveling on or under slopes with glide cracks. Although triggering one of these is uncommon, should one release above you, consequences would be high. 

Significant moat at least 5 meters back from cornice on Seattle Ridge near the top of uptrack. At least one sled track took a quick dip. Photo by Paul Forward

Ski tracks above two glide cracks on Lipps SW face. These glide crack have recently opened and were not present a week ago.

In some parts of the advisory area 5-7′ of settled storm snow is sitting on 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. Limit your exposure time spent underneath large paths.

On the Sourthern periphey of our forecast zone such as Johnson Pass and Lynx Creek we have limited snowpack information. But we do know in 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.

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 affect the weak layer.