Wind Slabs
- Alta montaña
- Límite del bosque
- Bajo el límite del bosque
- Probabilidad
- Likely
- Tamaño
- 1–2
What is it? You are likely to trigger sensitive 2-3 feet thick slabs with last night's moderate winds and additional new snow. Expect to find these soft and hard slabs to be most sensitive in exposed middle and upper elevations. On Saturday, a rider in the Pole Creek drainage triggered a large wind slab that broke above them on the slope they were riding (observation here). Importantly, this slide occurred before the added load from recent snow and wind.
Where is it? You'll likely find slabs in upper-elevation terrain, near ridgelines, and mid-slope terrain features like ribs and gullies. The picture to the right/above depicts the terrain where you can find this problem. Slabs may extend down into middle-elevation terrain in areas where the wind has been blowing harder. Most of the recent triggered and natural avalanche activity occurred in the Galena Summit area and north into the White Clouds, where more snow has fallen over the last week.
How can you recognize it? Cracks shooting out from your skis or sled clearly indicate instability. Watch for drifts, dunes, and ripples on the snow surface. Wind slabs can have a smooth, chalky appearance and feel and sound hollow, like a drum. Wind-deposited snow will be stiffer and keep your skis or snowmobile on or closer to the surface. Some of these slabs might be masked by recent snow and be more hidden.
How can you manage it? You can significantly reduce your risk today by steering clear of wind-loaded terrain. Today's slabs might not behave like your "typical" wind slab. Various weak layers exist in the snowpack's upper 1-2 feet (watch the video at right/above). Because of this weak snow, today's slabs may break wider and deeper than expected from a "simple" wind slab.
ADDITIONAL DISCUSSION: The layers of weak snow in the snowpack's upper 1.5-2.5 feet are being pushed toward their breaking points. Up to this point, we've needed the additional weight and stiffness from wind loading to make avalanches on these layers. Wind slabs and loose avalanches (sluffs) can step down into these deeper layers, releasing a larger avalanche than expected (see the photo above/right for an example). You are more likely to trigger these avalanches on slopes greater than 35 degrees in sheltered slopes.
This large avalanche was triggered by riders in the Pole Creek drainage on Saturday, 2/25/23. It failed on a wind-loaded E/NE-facing slope at 9,800'. It appears to have stepped down to a deeper weak layer in the bottom right corner of the photo.
