East Slopes South

The persistent deep slab problem continues to warrant enhanced caution near and above treeline.  Although increasingly unlikely, a small avalanche or cornice fall can trigger these unsurvivable avalanches. Prudent travelers will discuss exposure to the deep slab risk as part of any trip plan.

A major storm cycle in February piled snow deeply over a weak mid-January crust-facet combo. This layer likely sits more than a meter down at mid and upper elevations in the East South zone.  The last very large, deep slab avalanches were reported over a week ago in the southern and central Cascades.  Some of these monsters released naturally several days after the last significant winter storm.  Most recently and closest to the East South zone, a large to very large avalanche naturally released on Spiral Butte, just east of White Pass (3/1). Very large deep slab avalanches (D3-D3.5) released naturally in the Crystal Mt backcountry (2/25), Saturday, and Sunday (2/26-2/28).  Each passing day without reported avalanche activity adds to our confidence and we've dropped the problem in some zones. However, we've had reports of a recent sudden planar result on the mid-January crust-facet interface in the Wenatchee Mountains (3/9) and we are concerned that the East South zone may share snowpack similarities. At this point, these avalanches are a very low likelihood event, but with devastating consequences. We think the deep slab should remain part of any trip plan discussion to reduce your exposure to large avalanche paths.

The February storm cycle also built significant and overhanging cornices throughout the Cascades. Spring-like showery weather will transition to full sunshine on Thursday. Sunshine will increase the risk of cornice fall and shallow wet avalanches on all aspects. A cornice fall in particular creates a larger shock to the snowpack and may increase your risk of a deep slab avalanche. Continue to give slopes below cornices a larger margin for safety.

Wind slabs formed by west winds over the weekend will be losing reactivity. They may be covered by an inch or two of snowfall accumulating Tuesday or Wednesday with light winds. They might be triggered on steep and unsupported slopes in the lee of ridgelines.

During the ongoing Covid-19 pandemic, continue to follow the latest guidance from local, state, and federal health officials. Avoid unnecessary risks that could impact first responders and stress medical resources.  Wear a mask when appropriate, practice social distancing, and consider recreating closer to home.