Avalanche Forecast

Steer around wind loaded features on slopes steeper than 35 degrees. Use caution just below ridges and avoid slopes where the snow is thickly pillowed and deep.

Avalanches will be easier to trigger as you climb higher in the mountains. Strong wind from the past 3 days has formed slabs near and above treeline. You can trigger these avalanches where you see fresh wind features. Older wind slabs will be harder to see, as they’ve been covered by recent snow. Probing for stiff snow just below the surface can help you identify these areas.

Release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Wind Slabs form in specific areas, and are confined to lee and cross-loaded terrain features. They can be avoided by sticking to sheltered or wind-scoured areas..

Wind Slab avalanche. Winds blew from left to right. The area above the ridge has been scoured, and the snow drifted into a wind slab on the slope below.

Wind slabs can take up to a week to stabilize. They are confined to lee and cross-loaded terrain features and can be avoided by sticking to sheltered or wind scoured areas.

Persistent slabs are difficult to predict and often break much larger and wider than you expect. Minimize your exposure to avalanche terrain:

-Limit the amount of time you spend near slopes 35 degrees and steeper.

-Put an extra buffer of terrain between where you travel and where avalanches could start.

-Stay well out from under large avalanche paths and identify safer areas to stop and regroup.

You are most likely to trigger these avalanches in the eastern portion of the zone. At the top of Stevens Pass, these avalanches are now difficult, but not impossible, to trigger. Persistent Slab avalanches due to old weak snow that formed in early December. If you dig in the snow, you will find a layer of sugar-like, facets and old surface hoar buried 5-6 feet below the surface.

Release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer, deep in the snowpack or near the ground. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage. They commonly develop when Persistent Slabs become more deeply buried over time.

Deep Persistent Slabs avalanches can be destructive and deadly events that can take months to stabilize. You can trigger them from well down in the avalanche path, and after dozens of tracks have crossed the slope.

A snowboarder triggered this Deep Persistent Slab near treeline, well down in the path.

Deep, persistent slabs are destructive and deadly events that can take months to stabilize. You can triggered them from well down in the avalanche path, and after dozens of tracks have crossed the slope. Give yourself a wide safety buffer to handle the uncertainty, potentially for the remainder of the season.