With clearing skies, light winds, some great powder conditions to be had, and some smaller avalanche issues in the top of the snowpack, it might be easy to forget there is a very large and deadly avalanche problem to deal with. The facets from January, that are now buried 3-6′ deep and have been responsible for countless large slab avalanches, continue to be our main concern. It was three days ago two large slabs were remotely triggered from 1,000′ away in the Grandview area and this type of scenario is still possible today and into the weekend. Areas with a shallower snowpack, such as the Summit Lake area, have a higher likelihood for triggering.
Why is this so tricky? It’s because the snowpack can ‘appear generally stable’. In this situation, it’s easy to focus on the current surface instabilities, listed below, and forget about what’s several feet below us. Additionally, triggering these large slab avalanches is becoming more difficult because (1) the thickness of the slab makes it harder to affect the weak layers, and (2) time is allowing the snowpack to slowly adjust to the weight of the slab. Due to the size and deadly nature of a potential large avalanche, along with the lowering changes a person will trigger one, we are in a ‘scary MODERATE’ avalanche hazard.
Current surface instabilities:
Wind slabs: Lingering wind slabs are still possible to trigger on steep wind loaded slopes and in steep rocky terrain. These were formed either in Tuesday night’s 8″ of new snow or hidden below that snow and formed during Sunday’s strong outflow wind event. Either way, even a small wind slab triggered in the wrong place can send us somewhere unforgiving.
Sun Effect: Solar heating in the afternoon may cause loose snow sluffs again today on steep southerly aspects.
Cornices: As always, give cornices a very wide berth and limit exposure under them.
Keep in mind, any one of the above issues on the surface has the potential to ‘step down’ and trigger a large slab. It’s also good to remember there has been very little traffic since the big storm last week. As we venture further into the hills during this clear sky period we need to consider a number of things:
- Areas that have seen little to no traffic this year are more likely to have a large slab release.
- Signs of instability are not likely to be present before a slope releases
- It could be the 10th person on the slope before it avalanches
- Remote triggering a slab from below, the side or on top is possible
- Consider the consequences if the slope slides, will debris take you into a terrain trap or fan out?
- This is difficult low probability / high consequence situation and our guard has to stay up
*If you’d rather leave these issues behind, sticking to slopes 30° and less, with nothing steeper above you, is a great way to enjoy the excellent powder.
Large slab that was remotely triggered on Monday, Feb 24th, in the Grandview area.
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Loose snow sluffs on the southerly face of Pk 4940 (south end of Seattle Ridge), viewed from near the Johnson Pass trail head. 
