Mysteries from the deep. New/Old Snow on Trestle Peak.

We set off on a leisurely tour to take in a couple of hours of outside time and to investigate the changes in the snowpack that have developed over the last 24hrs. Snowfall rates starting around 5 am had been between 1-3 inches/ hour. New snow accumulation by 14:00 was 40cm-60cm at 6700 feet, well below tree line. The temperature at lake level was above freezing mid-day and eventually dropped below freezing by mid-afternoon. Considerable settling and consolidation within the new storm snow were occurring all afternoon.

Our interest in the snowpack was with the interface between the hard, frozen layer from the previous storm and the new storm snow. We dug a pit on an east-facing slope on the shoulder of Trestle Peak below the abandoned train tunnel. The slope angle was consistently 35 degrees and open without any obstructions or obvious triggers. Although the new storm snow was already beginning to develop distinct layers, the result on the new/old snow interface was ECTN. See video.

That said, there is a ubiquitous weak layer that was felt throughout the area. In the video, notice the layer consisting of loose, sugary granules, which was likely the delightful corn snow that was experienced over the last few days. The weight of the new snow, on top of the old frozen layer would most certainly excite the weak layer and make an exuberant bed surface in the right conditions.

From the snow pit, we set off to adjacent terrain to see if we could find those conditions. Sure enough, on slightly steeper terrain, 40 degrees with obvious trigger points, we located several natural D1-D2 slides that had occurred in the last 24 hours. With a couple swift ski cut tests, were able to trigger slopes that gleefully cut loose on the old snow weak layer. See end of video.

Although our ability to affect the weak layer varied throughout the tour, it's reactive behavior once triggered, will prompt us to remain especially cautious over the next few days.