Avalanche Forecast

You may be able to trigger avalanches big enough to injure or kill you above treeline. Expect drifts to form at upper elevations with gusty southwest wind Tuesday night. Wind Slabs will be most prominent in the northwest end of the zone, near places like Stehekin and Holden Village where more snow will fall, as well as the usually windy parts of the zone, such as the Wenatchee Mountains. Steer around freshly formed drifts and wind pillows on leeward sides of ridges. 

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 small storm slabs by the end of the day Wednesday. These avalanches are most likely in the northwest part of the zone. In these areas, avalanches will be small near and below treeline. The likelihood that you'll be able to trigger these avalanches will be determined by the bond between new and old snow. Snow will fall on a variety of old snow surfaces, including moist snow and a recent crust buried around MLK weekend. Dig below the new snow to check for a possible poor bond.

Use small test slopes and quick snowpack tests to see if the snow slides easily on the old surface. Watch for fresh avalanches and cracks shooting through the snow. If you see these red flag warning signs, use caution on steep roll-overs and slopes steeper than 35 degrees. Avoid terrain traps where even a small avalanche could have serious consequences.

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.