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RegisterApr 6th, 2018–Apr 7th, 2018
Olympics.
Dangerous wet snow conditions will develop Friday night and Saturday. Avoid avalanche terrain if you see slab avalanches in areas of wet snow. Minimize your exposure to large avalanche terrain from above. Avoid slopes with terrain traps where even a small Loose Wet avalanche would have serious consequences. Shallow Wind Slabs may build above treeline late in the afternoon.
Rainfall late Friday night and Saturday morning will be followed by a cooling trend with snow levels falling to 5000-5500 feet in the afternoon. Windy conditions should also develop Saturday.
Large and destructive Wet Slab avalanches are likely Saturday, especially near and above treeline. One potential bed surface is the former Persistent Slab interface found on N-E aspects near and above treeline about 1-1.5 down. These avalanches may run naturally or be human triggered. Watch for liquid water reaching buried crusts or softer layers of snow, well-below the snow surface as a sign that Wet Slab avalanches could occur. Wet Slabs are dangerous because they are hard to predict, give little warning, and can be very destructive. If you see slab avalanches in areas of wet snowpack, avoid traveling in avalanche terrain. You may be able to trigger smaller Loose Wet avalanches more easily in the same types of terrain where the Wet Slab problem exists. Avoid slopes with terrain traps where even a small Loose Wet avalanche would have serious consequences.
Large or very large glide avalanches are possible in isolated areas with a smooth rock bed surface. In these specific terrain features, the entire snowpack may release if lubricated with water due to recent rainfall and sustained periods of above freezing temperatures. Look for glide cracks as a precursor that large and dangerous natural glide avalanches are possible. Glide avalanche releases are not tied to peak warming or rainfall and are difficult to predict.
Recent rain and warm temperature have weakened Cornices. Give Cornices a wide berth if traveling along ridgelines as they often break back further than expected. Be aware of overhead hazard if traveling on slopes with Cornices above as they may fail naturally or be human-triggered.
Rain will change to snow Saturday afternoon near and above treeline. Wind and new snow will form shallow Wind Slabs on lee slopes near and above treeline. Visual clues such as blowing snow, fresh cornices, and cracks in the snow all indicate that you could trigger a Wind Slab avalanche.
Periods of light rain and mild temperatures have caused wet snow conditions to extend into the above treeline terrain in the Hurricane Ridge area.
On Wednesday, shallow amounts of wet snow accumulated above about 5000 ft.
Older weak snow has been observed on N-E aspects near and above treeline above a crust over the last 2 weeks. This layer is generally 1 to 1.5 feet (30-45 cm) below the snow surface. Rainfall and continued above freezing temperatures Friday night and Saturday may allow Wet Slabs to fail at this interface.
There are no other significant layers of concern in the snowpack at this time.
Observations
On Friday 4/6, NWAC professional observer Matt Schonwald found the facets above a crust on NE aspects between 5200-5400 ft healing. While this interface may come into play with Wet Slabs Saturday, the Persistent Slab problem has ended. Matt also found glide cracks opening on the 20th of June path. Weak snow at the ground could allow the 85 cm of firmer snow above to fail as a Glide avalanche if thoroughly wetted. While he found other areas with glide cracks, they were not widespread. The snowpack on solar aspects is becoming patchy, especially below treeline.