Avalanche Forecast

Expect fresh wind slabs to develop and increase in depth quickly with fresh snow and strong winds forecast over the next 24 hours. Winds slabs will likely be found above and near treeline, but be wary of wind affected snow even in the upper reaches of the below treeline elevation band. 

Avoid freshly loaded steep slopes Thursday, watching for signs of cracking or hollow sounding snow as wind slab indicators. You can stay safe by traveling on ridges, wind-scoured areas and any slope less than 35 degrees.

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.

1-2 ft of snow may fall by Thursday afternoon in the Mt. Hood area. As terrain anchors (trees, rocks, etc) become buried, we can start to think about storm slab avalanches developing in wind-sheltered terrain on convex rollovers or steep unsupported slopes. Watch for signs of unstable snow during the storm and choose lower angled terrain if necessary.

Release of a soft cohesive layer (a slab) of new snow that breaks within the storm snow or on the old snow surface. Storm-slab problems typically last between a few hours and few days. Storm-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.

You can reduce your risk from Storm Slabs by waiting a day or two after a storm before venturing into steep terrain. Storm slabs are most dangerous on slopes with terrain traps, such as timber, gullies, over cliffs, or terrain features that make it difficult for a rider to escape off the side.

Storm slabs usually stabilize within a few days, and release at or below the trigger point. They exist throughout the terrain, and can be avoided by waiting for the storm snow to stabilize.