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RegisterApr 14th, 2018–Apr 15th, 2018
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In areas where you find cold dry snow, use visual clues such as fresh cornices and snow drifts to identify and avoid wind loaded slopes greater than 35 degrees. At lower elevations expect wet surface snow conditions due to warm air temperatures and rain. Use caution if you travel on steep open slopes at lower elevation where small avalanche may carry you into terrain with large consequences.
A relative break in the weather Sunday will allow recently formed avalanche problems time to heal. However, do not let your guard down. This winter storm has added new layers to our snowpack. Springtime weather and snowpacks can be tricky as they go through their transition from winter to spring. Rules-of-thumb we often use during the winter don’t always apply. If the sun comes out or clouds thin, expect snow conditions to changes quickly. Loose avalanche may occur naturally from steep terrain and slab avalanche may become easier to trigger.
New wind slabs have formed at higher elevations. They may be tough to trigger but a resulting avalanche may be large enough to injure or kill you. Use visual clues such as frim surface snow, drifts, and fresh cornices to identify and avoid wind loaded slopes greater than 35 degrees.
Changes in temperature during the storm have likely created shallow storm slabs on sheltered slopes. Use caution if traveling in areas with more than 6” (15cm) of recent snow. Take time to consider the consequences of the terrain. Would a small avalanche take you off of a cliff or into a gully? If so, would another route be better?
At lower elevations, expect wet surface snow conditions. New rollerballs, fan shaped avalanche debris, and periods of rain on snow all suggest that you are likely to trigger a loose wet avalanche on similar slopes. Don’t underestimate the power of even small loose wet avalanches. They may carry you into or over slopes where even small avalanches can have large consequences.
Other springtime hazards are present in the mountains. Cornices have begun to droop. Glide cracks have formed on steep smooth slopes. Creeks are opening at lower elevations. Use caution if you travel near or below any of these hazards.
Around 6-8” (15-20cm) of new snow has fallen near Washington Pass over the last few days. Air temperatures reached above freezing at Pass level for much of the day Saturday. Moderate southwest winds likely transported snow near ridgelines forming new wind slabs on lee slopes
Generally warm weather over the earlier in the week allowed the upper snowpack to gain strength. Several freeze and thaw cycles likely created a strong surface crust in many locations.
We have very limited information about older persistent weak layers in the Washington Pass area. You are most likely to find a reactive persistent weak layer on shaded aspects or at higher elevations above recent rain events. If you have any information on snowpack conditions consider sharing your observations with NWAC on our public observations page.
Two common persistent weak layers seen in the Northeast Cascades are:
Lower elevations further east of the crest have melted back for the season and no longer present an avalanche risk.
Observations
On Friday, WA DOT reported several avalanches 3.5 feet deep near Cutthroat Peak as they cleared Highway 20. Although the exact weaklayer was not confirmed, the depth suggests an older persistent weak layer from mid-february.