Extra caution is still advised this weekend. Our persistent slab problem has not shown signs of strengthening. We’re still getting reports of very sketchy conditions. The weakness is 70-100cm deep beneath hard wind slabs. This is a dangerous time to be in avalanche terrain. Remember that most avalanche accidents occur during times of Considerable danger.
Above 2,500ft Considerable
1,500 to 2,500ft Considerable
Below 1,500ft Moderate
Degrees of Avalanche Danger ?
Problem #1: Persistent Slab
Distribution: All aspects, especially wind loaded slopes and cross-loaded terrain features, treeline and up. Underneath the recent fresh snow, we have layered hard slab with lots of weak, facetted snow underneath. There’s also an old rain crust 70+cm down with facets above and below (see profile below). We’re seeing easy failures and propagation on these layers almost a meter deep, and this danger will persist for a while. These slabs are underneath the new snow, so you’ll need to be thinking about deeper layers and digging to assess them. This is a dangerous time to be in avalanche terrain.
Problem #2: Wind Slab
Distribution: Wind loaded lee slopes (all aspects) from treeline and up. NW winds last week and southeast winds Monday blew the new storm snow into fresh wind slabs at the top of the snowpack. Cold temperatures will limit the amount of bonding between these layers. These recent slabs have weak snow underneath and will be sensitive to human weight. Avoid wind loaded slopes 25-degrees and steeper.
Problem #3: Deep Slab
Distribution: Isolated, on wind-blown slopes with thin snowpack less than 1m thick. Generally around ridgelines, and anywhere rocks are exposed or thinly buried. All aspects. Elevations above 3000ft. In the Pass zone, there are extensive weak facets at the ground in any areas of thin snowpack. We’re now seeing natural slides on this basal facet layer in areas north of the Pass (see photo). Even in places with deeper snow, there remain trigger points near rocks/thin areas. If you were to trigger a slide on this layer, it would be a deep, wide, hard slab avalanche with deadly consequences. This is a low-probability high-danger situation that is very difficult to manage, so it’s best to exercise caution. Be very careful to avoid rocky trigger points and thin areas. Stick to slopes with a deeper, more uniform snowpack.
Recent Avalanche Activity
Although not widespread, we’ve had recent or fresh avalanches reported several days over the last week, including some that ran during the clear weather period after the last snowfall. Most slides have been D3, running about a meter deep on the troublesome facet layer we’ve been warning about. This includes some slides that have been remotely triggered from ridgelines.
Light snow Thursday night added up to 2-6″ over the mountains. Snow and clouds should clear out briefly on Friday. Winds will be light and northerly with alpine temperatures in the mid-upper twenties. Another shot of light snow is likely Saturday with some clearing Sunday.
Sunday-Monday snow totals were around 6-12″.
24-36″ of snow fell march 12th-17th. Snow ratios were near 20:1 for the most part.
Additional Info & Media
We’ve been getting widespread reports of sketchy conditions for the last several days. This includes lots of whumphing, shooting cracks, and fresh avalanche activity. Be conservative, and avoid avalanche terrain when possible.