Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Possible
- Size
- 2–3
It has been almost a week since the last significant avalanche on the Valentine's Day buried surface hoar layer. This is a good sign, but it doesn't mean we are out of the woods yet. From what we have seen in the field, folks have been doing a great job sticking to mellow terrain. That means there haven't been many slope testers edging into steeper terrain, so we don't have a good sense of how sensitive the weak layer is to human triggering. Based on past experience, buried surface hoar tends to remain human triggerable for a long time and can give zero signs of instability before a large avalanche releases.
Another tricky aspect of buried surface hoar instabilities is that our typical tools for assessing the snowpack are not reliable (snow pits, hand pits, test slopes, etc). You could dig a perfect pit and find nothing, then step onto the adjacent slope and trigger an avalanche due to the spatial variability of the weak layer. For that reason, it is important not to try and outsmart this type of problem. The only way to reliably avoid the potential for triggering a large avalanche is to continue being patient by sticking to low angle terrain and avoiding slopes that are connected to steeper terrain above.
Winds could be stronger near Seward today. So if you see snow blowing at upper elevations, keep an eye out for wind slabs forming along ridgelines, cross-loaded gullies, and rollovers at upper elevations.
Other concerns today include smaller avalanches releasing in the 6-12" of new snow from this week, loose snow avalanches on steep slopes triggered by the sun, and cornice fall. Any of these smaller avalanches could trigger a larger avalanche on the buried surface hoar.
Glide avalanches are also still an issue and we have seen several recent glide avalanches release near Girdwood this week. Try to avoid traveling underneath glide cracks or expose one person at a time to minimize time underneath these unpredictable hazards.