Avalanche Forecast

Strong westerly wind has formed fresh drifts on leeward sides of ridges at the middle and upper elevations in the past couple days. These avalanches will be bigger and more dangerous at higher elevations. Avoid drifted features and leeward start zones near the top of ridges. You may find more significant recent wind effects in the Wenatchee Mountains. However, drifts could be deeper closer to the Cascade Crest, where more snow has fallen since January 3rd. Suspect that older weak layers of snow could produce surprising avalanches if you find less than 4 feet of snow on the ground or if you are in the northern portion of the zone.

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.

You may be able to trigger avalanches where recent snow has accumulated in the past 24 hours or where you find lingering storm layers from the past couple of days. Avoid convex slopes and unsupported features. Use caution around slopes steeper than 35 degrees. Watch for stiffer snow, overlying softer snow. Use small test slopes and snowpack tests to look for recent storm layers in the top 1-2 feet of the snowpack. 

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.