Persistent Slabs
- Alta montaña
- Límite del bosque
- Bajo el límite del bosque
- Probabilidad
- Possible
- Tamaño
- 2–3
Last week's extended storm cycle clobbered the Western Smokys, Sawtooths, and Banner Summit with 3 to more than 4 feet of new snow. Numerous deep, destructive avalanches in the Sawtooths (see photo at right and in Media section) were revealed when the storm cleared on Wednesday. Persistent weak layers in this zone are now buried around 3 feet deep at middle elevations and beneath a 4-5+ foot thick dense slab at upper elevations (see photo).
The lack of snowfall and significant wind the last few days have provided our snowpack a much-needed breather. However, we're about to poke one last sharp stick in the eye of the persistent slab problem. Today will be by far the warmest and sunniest day since the start of the January 10th storm cycle. To reduce the likelihood of triggering a persistent slab avalanche today, I'd recommend three things:
- Choose moderate slopes with low consequences. With a persistent slab problem, this is our primary line of defense.
- Avoid slopes with shallow and/or rocky areas. The weak layer will be closer to the surface and more easily impacted.
- Avoid slopes that are facing the sun today. The warming temps and sunshine may be adding more stress to buried weak layers.
While triggering deeply buried weak layers is more difficult, remember that the resulting slide would be catastrophic and likely unsurvivable.
ADDITIONAL DISCUSSIONObservers in upper elevation terrain continue to report that wind slabs are becoming less reactive. This doesn't mean you should stop monitoring the effects of wind as you travel. Wind-affected terrain often has areas where the snowpack is thinner, making the weak layers described above more easily impacted by your weight.