Turnagain Pass

The weak snow that formed in early December sitting over the Thanksgiving Rain Crust or old hard snow is now buried under 2-4′ of snow. This combination is our current cause for concern and heightened caution in the backcountry. Many large avalanches ran during the storm Saturday including a large D4 avalanche in Silvertip drainage. 

Yesterday several small skier triggered slab avalanches were reported near Pastoral above 3500’ on multiple aspects.  Two of these slabs may have been remotely triggered, a symptom of a persistent weak layer. No information is known about the weak layer/bed surface that caused these slides, but it is a good reminder that poor structure does exist within the top 2-4’ of the snowpack. This avalanche problem seems to be more reactive on the Southern side of Turnagain Pass and aligns with reports of snowmachine triggered slides in Johnson Pass and Lynx Creek two days ago.

Many people have been getting into steep terrain without issue, but these conditions warrant respect. Triggering a slab 2-4’ is possible in steep terrain and will be more likely in thinner areas near rocks and on unsupported convex features. Choose your terrain wisely and avoid slopes with high consequences. 

An avalanche that occured at the end of the Dec.19th storm had a long connected crown, just under 2 miles long on a ENE aspect of Twin Peaks ridge above Silvertip Creek. 

Multiple days of cold temperatures have been decomposing the top 8-10” of snow creating very weak surface snow. Yesterday a fast moving loose snow avalanche ‘sluff’ caused a skier to be knocked down and drug into an alder patch. Although it is unlikely that this avalanche problem will bury a person, it is capable of causing serious injury. The best way to manage a loose snow avalanche is by choosing terrain with low consequences and allowing the ‘sluff’ to pass by you while descending.

*Looking forward into the weekend a large storm is expected to arrive tomorrow morning and the current surface snow conditions (near surface facets and widespread surface hoar growth) will be a future layer of concern once burried.

Yesterday 15-30mph Westerly gusts were recorded at various ridgetop weather stations and several groups observed drifting snow along ridgetops. Although this wind appeared to be short lived, it did move some snow around in the upper elevations.  Be on the lookout for the following:

Cornices: Recent wind loading can make cornices extra tender. A cornice fall (like the photo below) could be a big enough force to awaken a persistent slab. Give these features plenty of space and be careful not to accidently drive your snowmachine out onto them or have your ski lunch break in the wrong spot. 

Windslabs: Should you see snow being transported by winds, this is a obvious sign that wind slabs are forming on leeward features. Pay attention for stiff, pillowed, sculpted snow and look for shooting cracks. 

A fresh looking slab was reported yesterday in Superbowl between Magnum and Cornbiscuit. The exact trigger and timing are unknown, but appear to have been triggered by a cornice. If anyone has information about this recent slab/cornice failure please submit an observation HERE.