Persistent Slabs
- Hochgebirge
- Waldgrenze
- Unterhalb der Waldgrenze
- Wahrscheinlichkeit
- Likely
- Größe
- 2–3
This has been a week of adding a little bit of stress everyday to the very concerning layer of buried surface hoar that exists 1 to 3' below the surface above 1,500' in elevation across forecast zones. A few inches of new snow was recorded yesterday morning and easterly winds picked up last night, which is depositing snow into new slabs in the upper elevations. We don't know how much stress it takes to overload this weak layer, and we are getting stable snowpit results within 50' of large human-triggered avalanches, which makes it especially unpredictable and scary. On Monday, March 17, after 2 days of calm weather with just a dusting of new snow and 30 tracks already on a slope, the 31st rider triggered a large avalanche and was caught and carried almost 1,000'. This person was able to ride away and you can get more information on this event in the video below. A lot of times this type of avlanche will give no warning and the safest option right now is to stick to low angle slopes that are not in the runout of anything from above.
Recent avalanches: There have been at least 4 human-triggered avalanches that we know of in the last week on the Seattle Ridge side of Turnagain Pass. We don't know why we aren't seeing as many avalanches on the east side of the road, whether it's less people getting out on steep slopes or something else, but we know this layer exists across zones and could cause a large avalanche anywhere.
Sun effect: Clouds are forecast to hang around most of the day, but things can warm up quickly, especially with a brand new layer of snow, if the clouds start to thin or if the sun pokes through. This shouldn't be too much of a problem today, but watch for roller balls as an indicator things are heating up in case the forecast doesn't match up with what's happening.
Cornices: Warming temperatures over the last few days may be weakening cornices. Include cornice avoidance in the route plan, whether it's giving them space on the ridge or watching out for them from below.
Glide Avalanches: Within the last 2 days, some movement in the massive south facing Cornbiscuit glide crack triggered a few storm slabs (see photo below). Avoid spending time underneath glide cracks or reduce exposure by spreading out or moving one at a time if they are unavoidable.
