Wind slab avalanche and surface hoar in Deep Creek

Our AIARE1 class toured into the Deep Creek area today to ski low angle terrain and investigate the avalanche problems brought on by the new snow. Leaving the trailhead around 10am, there was 3-4” of fresh storm snow on top of a rain crust layer from yesterday evening, and it was snowing lightly with a bit of sun peeking through some high thin clouds. The sun was short-lived, however, and for the rest of the day skies were overcast to obscured and we observed moderate to heavy snowfall until we left around 3:30pm. 

In a protected clearing at about 6800’ on a north aspect, we dug into the snow to look for buried surface hoar. We found large feathers, up to about 10mm, down 35cm. There was 22cm of new snow at this location at 11am, on a 3cm rain crust. We did a compression test and got a CTM SP result. 

Touring up higher, we noticed around 7200’ that we weren’t finding the rain crust beneath the new storm snow. 

Just below 7800’ on the north side of the ridgeline between Deep Creek and Pole Creek, we intentionally remote-triggered a D1.5 wind slab avalanche (video, at the pin drop location). The crown was close to 2 feet deep, and the avalanche was ~50’ wide and ran ~60’ down to the road cut below. In general we were somewhat surprised by how little wind we felt on the ridgeline, but there were still moderate gusts and we could use our poles to feel a dense, wind-deposited layer of snow with weaker snow below it and a few inches of soft new snow above it.

We skied low-angle, gladed, northerly terrain down to 7200’ and dug to investigate the surface hoar there. It was much harder to identify at that location, but we faintly noticed the surface hoar and got an ECTP 25 result down about 50cm. 

We toured back up to the ridgeline in order to ski down the ridge to the east back towards the trailhead, and noticed moderate winds blowing from the west northwest. Back at the cars, we noticed there was about 14” of storm snow on the rain crust from last night.