Northern Gallatin

From Obs: "This slide on the ridge extends north from Blackmore above Blackmore lake. The slide was on a north-facing slope around 9,100'. The crown looked multiple feet deep and either meandered, partially hidden from view, by another ridge or a substantial second avalanche a hundred feet away." 

Driving back from Grotto Falls trailhead, from the east side of the reservoir I could see this slide on the ridge that extends north from Blackmore above Blackmore lake. The slide was on a north facing slope around 9,100', large enough to see with the naked eye and clear as day with binoculars. The crown looked multiple feet deep and either meandered, partially hidden from view, by another ridge or a substantial second avalanche a hundred feet away.

Stable snowpack between hangover and upper green sleeves (ugs) while hiking. As soon as we crossed into the wind loaded gully we experienced increasingly slabby snow structure with failure. No snow pits or stability tests

Went up the east ridge of Mount Blackmore this morning. Winds were strong in the basin and along the ridgeline from the SW. Lots of snow being transported and wind slabs forming.

Dug a pit on an SE facing, 23deg slope at 9500ft out of curiosity to see what the pit would tell me in contrast to the giant avalanche from a few days prior. Facets at the ground were about 175cm from the surface and unreactive in my CT (had a CT5 on a density change about 8" down). Switched to a deep tap and got a DT4 with a dramatic sudden collapse. Skied a few laps in the low angled trees. Had some wind slab cracking along the ridgeline but otherwise no other signs of instability.

Back side off top. Wind blown. Skied in, not sure when it broke. Continued skiing to the lower angle terrain a short distance away.

We saw this crown on 2/20/21. It likely broke 2/19 or 2/18. Photo: GNFAC

We saw this crown on 2/20/21. It likely broke 2/19 or 2/18. Photo: GNFAC