This weeks weather is easier to summarized than the last two weeks. There were no storms bringing feet of snow, just the occasional inch or two here and there. It may come as a surprise considering the lack of any major weather events but this week was marked by significant avalanche activity.
The week started with the avalanche danger trending downward. Monday and Tuesday delivered 0-2 inches of snow and cool temperatures. There was a mild inversion mid-week that led to above freezing mountain temperatures. More scattered snow showers brought the occasional inch of snow sporadically through the week. A very brief period of mountain rain up to about 6,000 feet Friday night and into Saturday led to some more light snow Saturday morning. Winds were unremarkable for the most part over the week as well. Without much new snow or significant wind the avalanche danger should have continued to decrease but ultimately stalled.
The delay in decreasing the danger was caused by the Thanksgiving crust. Last weeks storm cycle brought enough snow to bury the crust and facets deep in the snowpack. As the storm slabs settled the now deep persistent weak layer is harder to trigger. That said, we had numerous reports and observed several large avalanches that failed all the way down to the Thanksgiving crust throughout the week. Shallow areas and locations with wind slabs were able to step down to the facets and crust. The likelihood of triggering the deep persistent layer is low but if you do, the resulting avalanche would probably not be survivable. Many slopes in the region have stabilized but there are a few that just can’t be trusted considering how large the avalanches could be. Expect to keep hearing discussions about the Thanksgiving crust as this problem wont be going away any time soon.