Persistent Slabs
- Alta montaña
- Límite del bosque
- Bajo el límite del bosque
- Probabilidad
- Possible
- Tamaño
- 2
Recent Avalanches: There have been two remotely-triggered avalanches on the south side of Tenderfoot last weekend. One occurred on Saturday, which was triggered by a skier ascending the ridge. The other was triggered on Sunday by people riding an adjacent lower angle slope. Another recent avalanche released during the storm last week at about 4,600' on a west slope of Hale-Bop. Several new glides were noticed on Tri-Tip, Fresno, Frenchy, and Butch.
There are several layers of surface hoar buried in the snowpack across zones and this type of weak layer is tricky and more difficult to assess.
What we know: The remotely-triggered avalanches mentioned above mean this layer was very sensitive just 3 days ago. People are finding the weak snow on east and south aspects between 2,000' and 4,400' ususally about 1 to 1.5' below the surface right now. So far all test results on these layers in Summit have been unstable. Surface hoar can be an untrustworthy layer and if triggered, an avalanche would be large enough to bury a person so the consequences could be terrible.
What we don't know: We don't have information from north and west aspects since this layers got buried. The most recent observations have been from Fresno and Tenderfoot so we don't know if these layers are as reactive on other mountains in the area. With the tricky nature of this weak layer it may not give warning signs and we don't know exactly where the trigger spots are located (usually thinner spots in the snowpack near rocks).
What can we do about it: We can completely avoid this problem by sticking to slopes below 30 degrees with nothing steeper above. If steeper terrain is in the plan, a terrain progression including starting with smaller slopes with lower slope angles is a good way to approach a suspect snowpack. With the depth of these layers a snow pit is going to be the best assessment tool, but the snowpack is highly variable so a stable result in one area doesn't mean the next slope in either direction is good to go (or even the slope with the stable result). Safe travel protocols will help if we get surprised, which include one rider on steep slopes at a time, choosing good safe spots, and watching our partners closely. Ensure the group does a good safety check of all equipment (transceiver, airbag, radios, satellite communications) before leaving the parking lot.
