Turnagain Pass

Above 2000′ a widespread layer of buried surface hoar remains a concern on steep slopes, where triggering an avalanche 2-3’ deep is becoming tougher by the day as the snowpack slowly stabilizes and adjusts. Relatively calm weather this week has allowed for folks to push further into the mountains with no reports of avalanche activity since last Saturday (2/18). However, this weekend it is important remember that poor snowpack structure still exists and triggering a slab avalanche could have high consequences. 

Yesterday stability tests on the West face of Corn Biscuit were a bit alarming with propagation on the buried surface hoar layer as well as near the ground on basal facets. These kinds of stability results are confusing when you see dozens of people ski/ride steeper parts of the adjacent slope without incident. This is an example of the high level of uncertainty with this type of avalanche problem. Tipping the balanche may require a big trigger (snow machine or multiple people on a slope) hitting just the right trigger spot. Thinner areas of the snowpack in steep terrain near rock bands or scoured features are places to avoid. A helpful way to think about this problem is to consider the consequences of a slope if it slides and identify and avoid terrain traps (gullies, cliffs, or trees below). Be aware that obvious clues like “whumpfing” or recent avalanche activity are unlikely. 

Deep Persistent Slab: We continue to find various layers of weak faceted snow and depth hoar near the bottom of the pack in certain areas. This includes Summit Lake zone, and some areas in Girdwood Valley and towards the Southern end of Turnagain near Johnson Pass. Similar to the problem above, these layers will be very tough to trigger, but a possibility remains in places with this structure. 

Wind slabs: Loose surface snow and brief periods of moderate winds this week have formed shallow wind slabs in the alpine. Today expect ridge top wind to be in the 10-20mph range from the NW – this wind direction can funnel through some parts of Turnagain Pass from a Southerly direction. There remains plenty of snow available for transport and newly forming shallow wind slabs will be possible a variety of aspects. Watch for pillowed or drifted snow or where the snow may feel stiff and ”upside down.” Identify steep features like convexities or gullies where a shallow wind slab could knock you off our feet. Blowing snow and shooting cracks will be obvious clues to look for if the wind pick up today. 

Loose snow avalanches: The top 6” of surface snow is loose and sluffs may be easy to initiate and fast moving on steep terrain features protected from the winds. 

Cornices: Remember these unpredictable hazards can break farther back onto a ridge than expected and have the potential to trigger an avalanche on the slope below. Give cornices extra space and avoid being under them. 

Glide avalanches: There is a new glide crack above the flats along Seattle Ridge, just looker’s left of the up-track and Repeat Offender slide path. Avoid hanging out under this crack and any others you may see – these release without warning and are very destructive.

Sunshine: Today skies may be partly sunny and solar warming may trigger loose snow avalanches in steep Southerly aspects. 

Large cornice on SW aspect of Magnum

Glide crack on Seattle Ridge has been slowly opening throughout the week