Avalanche Forecast

Today is not the day to go into avalanche terrain. If you venture into the backcountry, you must be confident of your ability to avoid avalanche terrain and stay off of slopes steeper than 30 degrees. You can trigger very large and deadly storm slab avalanches. Avoid drifts and steer around areas where the wind has stiffened the snow on leeward slopes at upper elevations. Use small test slopes to check how well the snow is bonding.

Up to 3.5 feet of warmer, more cohesive snow will fall on softer storm snow from the past 3 days. This will build a classic "strong-over-weak" layering, making slab avalanches easy to trigger. Southwest wind will form deeper drifts near and above treeline. The new snow has hidden older stiff wind slabs. 

In some locations, there may be a layer of weak sugary facet just above a very pronounced crust. So far we haven’t heard of any avalanches on this layer in this zone, but observers in the neighboring Snoqulamie pass zone remotely triggered persistent slab avalanches on Monday. If an avalanche occurs on these facets, it could be very large and destructive.

We want to draw particular attention to areas further south in the zone. Areas near the Columbia River, Mt Adams, and Mt St. Helens could receive substantial amounts of snow.

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.