Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Likely
- Size
- 1–2.5
Last night's storm brought roughly 4-6" of new snow to Girdwood and Turnagain Pass with higher totals near Portage. This additional load combined with wind loading from very strong east winds and another 4-6" of snow expected today will make large natural avalanches 1 to 3' deep on persistent weak layers possible. In the past week, we have seen many human triggered avalanches in the Seattle Creek area, and we expect human triggered avalanches to remain likely today and increase in size with the new snow.
So far, recent avalanche activity has been limited to Seattle Ridge and the north end of Turnagain Pass, but this additional load might be enough to make the persistent weak layers capable of producing avalanches across a wider swath of the forecast area. You can use test slopes, hand pits, and snow pits to check whether the buried weak layers exist in the area you are traveling and whether they are reactive to the weight of a skier or rider.
With persistent weak layers, avoid the temptation to try and outsmart the problem. If you are seeing any signs of unstable weak layers, we recommend taking a conservative approach and sticking to low angle terrain to avoid this issue. Avalanches releasing on lower angle slopes than normal and remote triggering is common, where you can trigger an avalanche from low angle terrain onto adjacent steeper slopes.
Cornices could fail naturally today as the added snow and wind cause them to grow larger. Keep an extra safe margin if you are traveling along ridgelines and try to avoid being underneath cornices that are being wind loaded.
Glide avalanches are still a concern across the forecast area. Try to avoid spending time underneath glide cracks to limit your exposure to this unpredictable hazard.
(2/26/2025)
Buried surface hoar at the crown of one of the recent avalanches in Seattle Ridge area. We saw probably 10 recent avalanches that had similar character. This one was in Main Bowl and occurred on Saturday.
Photo: Andrew Schauer
