Turnagain Pass

Wind slabs: Loose surface snow combined with Easterly ridgetop winds in the 10-20mph range could form shallow wind slabs on leeward features. The snow may feel “upside down” with slightly stiffer snow over softer snow. Look for areas of pillowed or drifted snow and identify steep features like convexities or gullies where the snow may be more loaded. Triggering even a small wind slab could have high consequences in the wrong terrain. Blowing snow and shooting cracks will be obvious clues to look for today. 

Loose snow: Yesterday small natural point releases were observed during the heat of the day as well as some human triggered sluff. The top 6” of surface snow is loose and may be easy to initiate and fast moving on steep 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 are expected to be partly sunny and solar warming may trigger loose snow avalanches in steep Southerly aspects. Sun combined with warm temptures could also make it easier to trigger a cornice or deeper instabilty (persistent slab) on Solar aspects. 

Cross loading pattern along South facing gullies on the SE face of Seattle Ridge as well as scoured ridgeline in the foreground. A good example of where wind slabs may be tender.

Skier triggered sluff on Tincan SW aspect just below CFR ridge, captured yesterday 2/22 on the DOT time lapse web cam. 

Clear skies over the last two days have allowed more folks to push further into the mountains with no reports of avalanches being triggered since last weekend. Unfortunately poor structure is still a concern throughout our region and triggering a large propagating slab 2-3’deep is still possible. A weak layer of buried surface hoar and/or faceted snow remains a concern on all aspects and elevations surrounding Turnagain Pass and Girdwood. A dense slab sitting on this weak layer has been slowing adjusting making this problem more and more stubborn to trigger with time. This means the probability of triggering a large avalanche is decreasing, but the consequences remain high, should someone find a trigger spot. Trigger points are often where the slab is thinner, near rocks or scoured areas. Also keep in mind, these slabs can break above you, and release after the 3rd, 5th, or 10th person has been on a slope. The trickiest part about our current snowpack is how difficult it is to assess due to the spacial variability of the weak layer, the slab thickness, and even the bed surface in some places. Be aware that snow pits and stability tests may not be representative of the actual slope you are trying to assess. A helpful way to think about this problem is to consider the consequences of a slope if it slides and indentify terrain traps (gullies, cliffs, or trees below.) Then decide is it worth the risk. Remember the steeper the terrain the higher the likelihood for triggering. 

In this snowpit on SW aspect of Sunburst buried surface hoar was found ~3′ below the surface and was very difficult to trigger in stability tests. 

In some places within our forecast zone at the bottom of the snowpack are various layers of facets with varying degrees of strength. In the Summit Lake zone and some areas in Girdwood Valley and Johnson Pass depth hoar has been found. The Valentines Day Storm cycle tested these layers with only a few avalanches occurring near the ground in (Girdwood Valley, and Summit Lake). Similar to the problem above these layer will be stubborn to trigger, but a possibility remains in places with this structure. The more likely scenario is where an avalanche occurring in the upper layers of the pack has the potential to step down and release the entire snowpack. If this does happen the volume will be large and could run long distances.