Heavy snowfall over the past week has been a good test for the persistent weak layer (PWL) of faceted snow that developed during the cold dry period in mid November. This weak layer exists on all aspects and has produced several large, natural avalanches on steep, northerly aspects, as well as a couple on southerly aspects. Any natural activity will be over by now. The weak layer may be showing signs of gaining strength, but it is still too soon to jump into avalanche terrain. Deep and dangerous human triggered avalanches remain likely. The snowpack simply needs more time to adjust after such a big loading event. The sun will be shining and bulls eye clues of instability will be less obvious today. This is the kind of day that is primed for an accident and has me worried. For now, this PWL should be presumed guilty until proven innocent and slopes steeper than 30 degrees should be avoided.

We dug this deep snow pit on Monday on a northerly aspect below treeline. The weak layer of concern is visible as a band of dust just above knee level. The overall depth and strength of the snow above the weak layer suggests we are moving in the right direction. Check out my complete observation here.

With about 20 inches of dry, unconsolidated snow on the surface you can expect to trigger loose dry snow avalanches in steep terrain. This type of avalanche can be especially dangerous in terrain traps like gullies, creeks, and road cuts. Travel advice remains the same, avoid slopes steeper than 30 degrees.

Trend: Decreasing

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