Turnagain Pass

Northwest winds are forecast to impact the advisory area today blowing 10-20 mph with gusts into the 30s and 40s. There is snow available for transport. Watch for blowing snow and expect slabs to become more stiff and connected in the Alpine. This wind pattern is opposite the loading direction from the storm this weekend. Be on the lookout for drifting and cracking and listen for hollow sounding snow indicating harder slab over soft snow. Observers yesterday reported an ‘upside down’ snowpack from the weekend’s snow and wind, hand pits failing on isolation and triggering small steep convexities. There was one remotely triggered small slab in Common Bowl on Tincan. Steep, unsupported slopes (35 degrees and steeper) that are wind loaded will be the most suspect today. In addition pay attention to direct sunshine. Steep southerly slopes protected from the wind may see some roller balls and may be more prone to triggering with warming as the recent storm slab becomes more cohesive. Remember slab depth may be thicker on the northern end of Turnagain Pass, in Placer, Portage and Girdwood. More snow fell in this part of the advisory area over the holiday weekend. Practice safe travel and evaluate snow and terrain carefully. Cornices are looming large in some of the Alpine terrain. Give them an extra wide berth as they often break farther back than expected.

Remote triggered small slab on Tincan Common, 2-18-19. Photo: Amanda Compton

 Hand pit failing on isolation on Sunburst at 2700′, 2-18-19. 

Periphery zones such as Summit Lake and Johnson Pass harbor a poor overall snowpack structure with a variety of weak layers. From Girdwood to Turnagain Pass roughly 2-3′ below the snow surface sits a layer of buried surface hoar.  Although these persistent weak layers have not been reactive lately, additional load from recent snow and increasing winds may start to tip the balance. It is good to keep in mind that triggering an avalanche today could to step down into old weak layers and initiate a larger more dangerous slide. This is more likely in and around Summit Lake where the structure is the most suspect. 

Glide cracks are unpredictable, not associated with human triggers, and can release without warning at any time. The best way to manage this problem is to avoid traveling on slopes directly below glide cracks.