We have seen 19 days without any precipitation and eight days since a wind event impacted our region. Although the snowpack is pretty tired, a hard wind slab 12-18” deep was triggered by a snowmachiner two days ago on a SE aspect of Seattle Ridge. This is a good example of a wind loaded terrain feature still harboring unstable snow. Its also possible the sun and daily warming helped tip the balance. As you travel today, monitor the snow for damp or wet surfaces or new roller ball activity near rocks. These are obvious clues that the sun is impacting the snowpack and may increase the potential for triggering an old wind slab or wet loose avalanche. Kicking off even a small wind slab or loose snow avalanche in steep terrain may have high consequences. Things to keep in mind if you are headed to the mountains today:
Wind Slabs: Old and hard winds slabs are easy to find but for the most part they are locked into place. Smooth pillowed snow on steep features or in rocky areas will be the most suspect zones for someone to initiate an old wind slab.
Loose Snow Avalanches (Sluffs): Dry sluffs on steep slopes are probable and have been fast moving this week. And, as mentioned above, wet loose (or damp) sluffs, both natural and human triggered, may occur.
Glide Avalanches: Glide cracks continue to slowly open above popular terrain on Seattle Ridge and in other areas of the advisory area. These could release at any time, watch for these cracks and avoid being under them.
Cornices: Cornices may start to loosen with daily warming – as always, give these monsters a wide berth from above and limit exposure time traveling underneath.
Persistent Slabs and Deep Slabs: There are various weak layers in our thin snowpack. Buried surface hoar sits 1-3+’ below the surface and faceted snow sits in the mid and base of the pack. These weak layers with varying degrees of strength are in a dormant stage due to plenty of time to adjust with a lack of changing weather. Although its unlikely, an avalanche breaking deeper in the pack isn’t completely out of the question in Johnson Pass, Lynx Creek and part of Girdwood Valley.
This hard wind slab was initiated by a snowmachine just below the trees, lookers left side of photo, while exiting the slide path. This was on a SE aspect of Seattle Ridge at 2400′ in an area near ‘God’s Country’. Photo by Brian Bird.
Also note the numerous glide cracks along Seattle Ridge SE face.
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