East Slopes South

Daily deep slab failures in the Cascades continue to keep professionals off large avalanche slopes. The risks of such a low-likelihood but catastrophic avalanche should be discussed in any trip plan. Forested, flat, or smaller terrain features will help limit your exposure.

We're not out of the woods yet in the southern and central Washington Cascades. Monday was several days removed from a major storm cycle and a very large natural avalanche occurred on Chair Peak at Snoqualmie Pass (NE-E-SE 5800; HS-N-D3.5/R4-O). At the boundary of the East South zone, observers just east of White Pass saw evidence of large avalanches that released last week.  Deep and large natural avalanches were observed in the Crystal backcountry over the weekend. The avalanches east of White Pass were not as deep or widespread as those in Crystal or in the Central Washington Cascades.  We still have plenty of uncertainty about deeper weaker layers, but we think that they remain in the snowpack. Limit your exposure to large open slopes and favor terrain below 35 degrees. Getting caught in a deep slab avalanche would be fatal, justifying avoidance of large avalanche paths despite the low likelihood of failure. Large and sagging cornice failures or smaller avalanches you trigger represent the most way to wake a deep slab, but humans or snow machines may still disturb these layers.

Mild temperatures reaching into the 40s at 5900 ft on Monday should have accelerated the healing process for wind-drifted slabs at upper elevations.  However, on shaded aspects, that healing process remains slower. Recent wind slabs may have formed further below ridgelines than you expect, given recent extreme winds.  Moderate westerly winds Monday night may have added shallow fresher drifts on these same northerly aspects. Identify wind-affected slopes by looking for textured or wind stiffened snow and cornices. Where you see these signs stick to slopes under 35 degrees and avoid steep start zones such as slopes near ridge crests. Cornices will be large and may be easy to trigger along ridgelines.  Give them a wide berth as they often break further back than you expect.  

With cooler air moving in Monday night, expect the risk of loose wet avalanches to diminish. However, sunshine may still break down the crusts on steep southerly slopes to produce small wet avalanches.

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.