Snow Observations List

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. 

These avalanches were reported yesterday 12/15 by ski patrol who heard them run and saw debris around 1230. They broke naturally towards the end of a period of heavy snowfall that totaled 10"=1.22" SWE. Photos taken 12/16 at 1045-1100.

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. 

Dug on a NE aspect on The Ramp at about 8500’. HS was around 100 cm but varied quite a bit. There’s a layer of very weak facets about 40cm down from the surface that are particularly concerning to me. The storm slab I observed yesterday is also still quite reactive, but the snowpack seems to still lack a significant slab on the aspects where I’ve been traveling. There was an abundant amount of cracking in the newer snow whenever traveling off a beaten path. In our pit, got results of CT3 SC and CT7 SC on the storm slab fracturing at the interface with sudden collapse character. The layer of facets farther down in the snowpack collapsed at CT10 SC. I also performed a PST on the weak layer of facets and the weak layer probated to end at 35/100 cm. 

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 email: "Steve Harvey and I did a quick pit yesterday (12/16/2024) S. of Cooke in Republic Creek. E. aspect; 9.085'; 30° slope; HS 80 c; 12:30PM, Calm/cool (teens), Lt snow.

ECTN21; ECTP24 at 50 cm on buried facets. We declined to continue on slope.

We didn't perform a detailed profile, but generally, fist (new snow) and 4-finger above buried facets and progressively 2-finger to 1-finger below.

Noticeable Issues:

(1) Low and variable snowpack, 30cm or less under/near trees and on wind-scoured aspects and loading in fetch zones. Something to keep in mind as season progresses with  potential sweet spots in predictable places.

(2) Buried 50 cm facets/hoar that is essentially everywhere in Cooke City zone.

(3) We did not observe buried deep facets at the base of the snowpack."

Skied Bacon Rind meadows today. Didn't look at the Skillet.

S1-S2 all day, L-M winds from the south

HS of 45cm at the road and 65cm at the ridgeline. It is more or less entirely faceted and unsupportable. Ski pen of 40cm and boot pen to the ground.

Skiing was good but hazardous. Lots of audible rock strikes, and getting through the trees back to the road was challenging.

Not recommended yet.

Came across small debris pile while setting a skin track up to Texas Meadows from Bradley Meadow/Wolverine area. No other signs of instability. Texas Meadows showed facets down low and wind slab above. 

Headed up Blackmore Sunday 12/15, late morning, was pleasantly surprised by the amount of new snow. Not sure how much was brand new, but up below the summit seemed like about a foot of fresh. Skinned to the ridge above the east face, plenty of wind at the ridge, dug a out on the east slope just below the ridge a bit north of where most people ski down in snow that was not wind affected. Isolated column test clearly showed a weak bond between new snow and old, decisive ECT-P 5 on the extended column test. Skied the trees out.

On our first column test was CTX and slid on the saw cut, in the video we didn’t get the same result but still very reactive.
 

During our extended column test we were at 9500ft on a North slope. 

ECTN second tap storm slab 

ECTN twenty three on ground facets 

from @brendan_durrum_photo

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

I observed a large whoomph about 150ft from the ridge (top of glades) going up Blackmore today while breaking trail. was definitely wind loaded area… I could feel the energy in the snowpack today once I got up higher, super sensitive it seems. ECTN 14 in my pit I dug lower down the meadow with no wind slab prevalent.

Small windslab triggered on approach for inspection. Failure interface had 5 mm Surface Hoar. Soft slab, remote propagation onto the adjacent slope. Debris covered about half of the road bed.

Sunday morning 12/15 we were skiing just Southwest of Henderson Mountain between the road cuts. The first skier in our party remotely triggered this slide from a slightly lower angle aspect about 50 ft to the skiers left of the slide where the snowpack was shallower. It broke on a convex rollover about 100 ft wide and ran about 80 ft. downslope. The crown averaged 30 inches and broke on sugary facets about 18 inches from the ground. No one was caught.

Skied into middle basin from Beehive this morning and found 8-12 inches of unconsolidated snow on top of a sun crust. While skinning back up to the Beehive/Middle ridge we remotely triggered 12 inches of storm snow on a SE facing gully from 15 ft away, the crown was ~50 ft long. ~8,200 ft. 

Winds increased throughout the morning, actively loading E aspects. 

We skied east and west aspects of Woody Ridge today.  It was snowing most of the day, with periods of heavy snowfall, which accumulated to about 4-5" of fresh throughout the day.

We found buried surface hoar in 3 different snowpits, on east and west aspects, between 9300-9700'.  In each place the SH was buried under about 25cms of new snow, and I would describe it as somewhat irregular/ inconsistent, and mixed with some other faceted snow types.  The SH crystals were generally about 2mm in size.

In our snowpit (file attached) at 9550', west aspect, HS 70, we had an ECTN12 at 45cms. (on that surface hoar layer).

No collapsing, no cracking.  No avalanche activity observed (low vis).

One additional note was that slopes exposed to the SW wind had a thin rime crust that appears to have formed last night.  The ridgeline was also noticeably rimed.  In areas this rime crust was up to 1cm thick and 1F hardness.  We were not finding this rime crust on leeward or sheltered slopes.

We rode into Buck Ridge on December 15. It was snowing and the wind was whipping up the snow that had already fallen, so visibility was limited. We rode in to the top of First and Second Yellowmule to get a closer look. The total snow depth (where it isn't stripped down by the wind) varied from 20 inches to a little over three feet. There was 6" of new snow. Similar to other areas, new snow is falling on near-surface facets. In wind-sheltered areas, there is insufficient slab to result in widespread instability, and the critical ingredient is wind-loading. We got ECTNs 5-14 on the weak layer buried 6-8" deep with no deeper failures.

I am always nervous during periods of incremental loading because we will eventually hit the breaking point. I'm avoiding wind-loaded slopes and testing the upper 2 feet of the snowpack to assess for instability before considering steeper terrain. 

About 6 inches of new snow at the trailhead around 9am. While touring to the ridge between beehive and middle basin we found strong wings actively loading east facing slopes. While moving north across the ridge, small test slopes showed cracking but no cohesive wind slabs yet. When skiing into middle basin, I stopped at the top of a convex roller and had cracks shooting out 50 feet in either direction from what seemed to be a soft slab in the new snow that slid about a foot or so. This was the most major sign of instability from the day. Lots of shooting cracks when skiing and skinning in the new snow. Throughout the day found anywhere from 8-15 inches of new snow, with the larger totals on wind loaded slopes.