Buried Surface Hoar and old Natural Avalanche below Ralston Ridgeline

Went out for a tour today on the south aspect of the Ralston ridgeline, seeking slopes on the part of the compass that does not have the November basal facets.Left the car around 10:45 am, with air temps around -3 C, light winds, and banners of snow blowing off the ridge up high. Did not notice any signs of instability on the way up, and probing in many locations revealed that the basal facets did not exist on this slope. However, we stopped to dig a pit at around 8000' on a SE aspect, and were in for quite the surprise. About 20 cm below the surface, we found a layer of buried surface hoar, underneath recent wind transported snow (see image). Winds had grown to moderate at this location, and were rapidly transporting snow, and blowing snow was bordering on intense at the ridge. This layer of buried surface hoar was quite reactive in our pits, failing in our CT at 1 tap, and propagating fully at 2 taps in two separate ECTs (see video). This came as quite a shock, and changed our plans for the higher slope. We did not find the basal facets in this location, and the rest of the stability tests were uneventful. Also of note were two crusts down low in the snowpack, with faceting rounds between these two. They showed no reactivity, and the rest of the snowpack was strong, rounded and well bonded. We did not experience any whumpfing, collapsing, or cracking on the way up.

Another hasty test pit dug at 8800' on a similar SE slope found this buried surface hoar as well, 20 cm below the surface in an 80 cm deep snowpack. This also failed at a CT12 SC. The basal facets WERE found in this location, and these failed at a CT19 SC down 60 cm. An ECT was not performed at this location, and we managed terrain carefully on our way down. The lower sun-exposed slopes, which had been moist on the way up, had developed a breakable crust, but by sticking to slopes with a more easterly tilt, we were able to find excellent ski conditions.

We did notice an old natural avalanche on the way down, on an E/NE facing slope, just on the lee side of the ridgeline. The crown was mostly filled in, so it was impossible to glean further details (see image).

Ultimately, quite a layer of concern for me, and one that does not open up the southern half of the compass to me.