20-21

Riders triggered this slide on 2/28/21 near Red Canyon/Cabin Creek, north of West Yellowstone. Nobody caught or injured, but close call.

Riders triggered this slide on 2/28/21 near Red Canyon/Cabin Creek, north of West Yellowstone. Nobody caught or injured, but close call.

Riders triggered this slide on 2/28/21 near Red Canyon/Cabin Creek, north of West Yellowstone. Nobody caught or injured, but close call.

Riders triggered this slide on 2/28/21 near Red Canyon/Cabin Creek, north of West Yellowstone. Nobody caught or injured, but close call.

"Saw this crown the morning of 2/28 from G1 while climbing." Reported to GNFAC (earlier in the week). Probably slid last week during other large slides nearby. Photo: V. Beineke

"This was observed from the genesis area in hyalite. It was on the north east facing Bowl off elephant mountain about 800ft above the un named wall." Photo: B. Durrum

This was observed from the genesis area in hyalite. It was on the north east facing Bowl off elephant mountain about 800ft above the un named wall. It looked like it was about 200-300ft across.

My partner and I planned to ski Hollowtop Mountain in the Northern Tobacco Root range and we approached from Cataract Creek Basin. As we traveled along the ATV road to the basin, we noticed a lack of snow in the basin and many wind-scoured slopes. Once we reached Lower Mason Lake, we had a pretty clear view of our route up Hollowtop and unfortunately saw that it was completely wind-scoured. Wind was whipping through the range and had scoured slopes on North, West, and East aspects - only the Southern aspects were spared but even then the snowpack was relatively shallow in places.

We performed a hand hardness and ECT test on a sheltered SE facing slope at 8850 feet of elevation with a pit snow depth of around 140cm. The hand hardness test revealed a well consolidated and rounded slab that is lying atop a 60 cm foundation of different facet layers. These were some of the largest facets I have seen this season! The ECT resulted in an ECTN 19 and ECTN 20 across different small crust layers about 20-30 cm under the surface. The fracture character for both breaks was PC, Q3. We then did an informal "Rutschblock Test" above our ECT cut. My partner went to the back of the ECT and stepped and then jumped onto the back of the block. After four hops, the ECT cut failed and after seven it fell over, breaking on the facet layer 60cm above the ground. This failure also clearly indetified several other slabs in the snowpack that did not propagate on our ECT but definitely exist. Pictures of those slabs, including the large consolidated blocks are included below.

We skied the south facing slope several times and noticed a lot of variability within the snow coverage of even that slope. The wind picked up throughout the day and a lot of snow transportation was visible.

Skied out on an open slope adjacent to Hyalite creek today. Dug a pit on an E facing 15 deg slope at ~7800ft. No notable results in CT or ECT, but when converting to a deep tap, DT9 on the facets at the ground with a big sudden collapse. Pretty consistent with other pits I've dug up in Hyalite in the last week. Basal facets are still very weak and unconsolidated. Did not see any other signs of instability but would not expect cracking or collapsing with the problem layer buried so deep (~6 feet in this pit).