Cooke City

Around 5" of fresh snow lay on top of the snowmobiles this morning in Cooke City. We rode up to Daisy Pass to visualize terrain and got eyes on Crown Butte. On the north side, we noted the crown of a wind slab avalanche (R1 D1) that broke during the storm cycle. We then rode back down and toured up Henderson Mountain along its SW flank. Skies cleared throughout the day and allowed for great visualization of terrain north of Cooke. We got eyes on Miller Ridge, Crown Butte, Henderson Bench, Scotch Bonnet and Sheep Mountain; we did not note any other avalanches outside of the small one up on Crown Butte. We saw extensive cross-loading in the bowl of Henderson Mountain and on Miller Ridge. 

We dug snowpits on SW and S aspects on Henderson. We noted buried facets a little over a foot deep on our pit on the SW and we got an unstable test result in our snowpit on the S aspect (ECTP 25) on a facet/melt freeze crust sandwich. 

Most notably, as we entered non wind-effected, upper-elevation terrain on Henderson, we consistently triggered many localized collapses and heard audible whumpfs, indicating persistent slab instability. 

Today, we rode up to the base of Henderson and toured up to the bench to check out the crown of an avalanche that occurred yesterday. The avalanche was remotely triggered by a skier from 50' away. It was about 100' wide, ran 50' vertical, and the max depth of the crown was 2.5'. It fractured on the interface between the new storm snow and faceted grains. This was a heavily wind loaded area with an HS of 179cm. Strong westerly gusts and heavy snowfall had nearly refilled the crown by the time we left. 

We then traveled further up the bench to a north facing aspect and dug again. Here we got an unstable test result, ECTP 13, on a layer of buried surface hoar. Faceted snow exists at the base of the snowpack but our main concern on non-wind loaded slopes is layers of surface hoar and near-surface facets buried about 50cm deep. It was snowing and blowing throughout the day, and with continued loading, we expect to see collapsing, cracking and signs of instability tomorrow. 

Went out north of Cooke City today for some skiing. Dug a pit at 9980' on a southwest facing, windloaded slope with a slope angle of about 15 degrees. We found 105cm of snow. Our ECT gave us an ECTP29 55cm up from the ground on what seemed to be the buried surface hoar layer. It was snowing and blowing all day out there. 

From IG: On 12/15 "Storm slab broke about 200’ above us as skinning up the hallway coming from the north side on the throne." Photo: Anonymous