Avalanche Forecast

Storm slabs up to 1 ft deep are possible by mid-day Friday. Slabs will be more deeply drifted near and above treeline on steep wind loaded slopes. If traveling into wind affected terrain, minimize your exposure to avalanche terrain by traveling on ridges and slopes under 35 degrees.

Below treeline, shallow storm slabs and small loose wet avalanches are possible depending on the amount of new snow received and how fast conditions cool. Avoid very steep open slopes with exposure to terrain traps where even a small avalanche could get you into trouble.

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.

A layer of buried surface hoar was responsible for many human triggered avalanches earlier in the week. This layer may be harder to trigger now, but the consequences will be higher if a new storm or wind slab avalanche steps down to where this layer is present. Prior to this storm cycle, the distribution of this layer had been more widespread in the Crystal Mountain area with greater uncertainty elsewhere in this zone.

Release of a cohesive layer of soft to hard snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slabs.

The best ways to manage the risk from Persistent Slabs is to make conservative terrain choices. They can be triggered by light loads and weeks after the last storm. The slabs often propagate in surprising and unpredictable ways. This makes this problem difficult to predict and manage and requires a wide safety buffer to handle the uncertainty.

This Persistent Slab was triggered remotely, failed on a layer of faceted snow in the middle of the snowpack, and crossed several terrain features.

Persistent slabs can be triggered by light loads and weeks after the last storm. You can trigger them remotely and they often propagate across and beyond terrain features that would otherwise confine wind and storm slabs. Give yourself a wide safety buffer to handle the uncertainty.