Snow Observations List

We skied north of Bridger Bowl today near the ramp. We dug at the top of the refrigerator chutes with an HS of 66 cm where 4" of new snow was on top of the existing weak snowpack. Here we had ECTN22 and ECTN16 results at the interface between early December snow and weak-faceted snow near the ground. We continued up the ramp towards the ridge where the wind was forming drifts of snow that were cracking at our ski tips. At the ridge, we were able to trigger a small avalanche on a test slope. 
Below the ridge, we dug another snowpit in an area that was not wind-loaded. Here the HS was 72 cm and had 8" of new snow. The same poor structure was found here and we had an ECTP 20 result on the same interface of December snow on weak early-season snow. 

While recent snow wasn't enough to dramatically increase the danger on the slope we chose to travel on doesn't mean that is the case everywhere. The snowpack structure in the Bridger Range is poor and careful assessment should be done if choosing to enter steep terrain. Slopes that have or are being loaded by wind will likely have easy-to-trigger wind slabs. 
As we skied back to the ski area boundary the wind had begun to form drifts at the lower elevations that were easily triggered.  

From email: "Continued, widespread collapsing today.  About 10 good ones, and that was with very minimal trailbreaking/ about 700' vert.

No new avalanche activity to report today.  But I did note a relatively fresh avalanche yesterday (12/22) north of Cooke.  It was on a SE aspect, about 8900'. Widespread propagation there.  

Widespread collapsing yesterday.  Approx 20 significant collapses.  Many shaking trees 50'+ away."

We snowmobiled up to 9,000' on Sawtelle peak, then skied to dig a couple pits. Our first pit was on an East aspect on a heavily wind loaded slope. The HS was 130cm (or 4.2 feet). There was 8" of new snow equal to 0.85" SWE, sitting over old consolidated snow that made up a slab over soft, weak facets about 50cm off the ground. We had ECTP24 x2 break on the old weak snow. Our second put was on a SW aspect and had an HS of 90cm (almost 3 feet). We got an ECTP19 here breaking on the same layer of very soft, weak facets. Wind was moderate out of the west-northwest with temps in the teens F. The new snow combined with the poor snow structure will increase avalanche danger this weekend. Video attached. 

Massive surface hoar on sheltered slopes outside of West Yellowstone 

We rode onto Tepee Basin and saw little change since the last time we were there on December 13th (see that here). What we did find is that the snow has become more supportable in some areas but the poor structure remains. In our stability tests we had low scores on both northern and southern apects, with ECTP11 and ECTP12 results on facets below early December snow. The snow near the surface has begun to facet and surface hoar can be found on many slopes. In some areas this surface hoar was large and rimed. 

As the snow returns areas with this poor structure will increase in danger. As the amount of snow increases so will the possibility of triggering an avalanche. 

Total snow depth 60cm

EctP16@22cm   South Aspect @7800ft

From YouTube comment 12/22/23: "I am an alpine climber - descended from Barronnette today, went south all the way down the ridgeline and descended the gully above the start of the XC trail. Heard 10+ instances of whomping and slope collapsing under my feet on both avalanche and non-avalanche slopes on N & E aspects."

Pretty sure that’s an avalanche. Thought it might be goat tracks or something but you can see were some debris went through the slope below the cliff. The left side looks like it could’ve gone recently, but I couldn’t really tell. 

HS 55, ECTN11@33, 28 degree slope, 80 degrees E. Upper snowpack is faceting, lower snowpack is depth hoar. Surface is sun affected and has breakable melt freeze crust on all non shaded slopes. No obvious signs of instability observed. 

Toured into Divide Basin yesterday (12/21). Saw evidence of two natural avalanches on southwest aspects (see photos). The age of these slides was hard to gauge based on our lack of recent snow. I toured to a south aspect adjacent to the south face of Divide Peak and dug a quick pit. Snow was ~65 cm deep. I did an ECT and got an ECTP3 failing on a facet layer overlaying a finger hard crust 31 cm down. Below the crust was fist hard facets to the ground. 

I decided to check out some other aspects in the basin. On the majority of shady aspects I found a uniformly weak snowpack and frequently sunk in facets to above my knees while touring. On aspects with supportable snow I experienced frequent and widespread collapsing.

We did a large loop north of Cooke City today. Signs of instability were easy to come by but we saw more of a mixed bag of test results. We started our day near Henderson Mountain, where, while ascending, we felt a few collapses. Our first stability test had ECTX results but lacked a slab on top of the weak snow near the bottom. We stopped 100' down-slope and saw different results, ECTP15 and ECTN15 above a crust. We rode across the valley, saw a very poor snowpack structure below Miller Ridge, and got varied results (ECTP15, ECTN15 x 3). Regardless of test scores, I have difficulty trusting such a weak snowpack structure.  

Finally, we rode back to Scotch Bonnet to see how things had changed since Sunday when Alex was there. The poor structure Alex saw on Sunday was still there, with continued unstable test results (ECTP16 on weak snow above a crust).

My partner and I felt better about the conditions today than yesterday at Woody Ridge. The weak structure around Cooke City is widespread. Safe travel requires careful snowpack evaluation, cautious route finding, and conservative decision-making. 

Toured into the southern Lionhead today. Yesterday’s warm weather made the snowpack more moist, and the upper snowpack was much more cohesive than in days past. Snow was glopping on skis and skins up to around 9k. I got on NE, E, and SE aspects, which were quite reactive, with more wumphs than in the last few days.

We were surprised by the abundant signs of instability nine days after the last measurable snow in Cooke City.

We toured up Republic Creek today towards Woody Ridge. When moving through fresh snow or stepping off the skin track, we felt many localized collapses. Near the top of the ridge, we felt a large collapse. Our stability tests showed worse test scores than expected, ECTP11. The bottom 55 cm of the snowpack was faceted and weak, on top of this was a slab that formed with early December storms. Collapsing, poor structure, and low stability test scores kept us out of avalanche terrain.

Alex was in Cooke City on Sunday and observed signs of instability and poor snowpack structure (Read his observations HERE). The poor structure and instability is more wide spread than we initially thought, and has not noticibly improved. 

Toured up bacon rind today (12/20) with the idea of skiing off Ernest Miller ridge. Temps were above freezing when we left the trailhead and up to 9000’. On our approach we had several collapses with cracks up to 15’ out. We found a HS of 50cm and had mixed results in our pit. We stayed in the glades below the ridge, the skiing and riding was quite good. Exiting the basin was a bit sporty with minimal snow coverage. 

Roller balls even on NE slopes around noon. Roughly 8000’ up Hyalite. Yuck. It’s hot. 

Rode from Doe Creek along Buck Ridge to McAtee Basin and the heads of Muddy and Bear Creeks. Snow cover is very marginal on the road - bounced along on the rocks periodically overheating for the first several miles. Snow depth improves as you gain elevation. Snow depth on flat or shady slopes above 8500 ft is approximately 2 ft. Sunny slopes have less snow and more rocks showing. 

Dug multiple quick pits and did two snowpit profiles, one in 2nd Yellowmule and one adjacent to an avalanche that looks to have broken last week along the divide between Muddy and Bear Creek. Found the same general snow structure as the rest of the advisory area - ~12" of weak faceted snow at the ground with a slab (~12") of early December snow on top. A mix of ECTN and ECTP results in the mid-teens across the two pits. Avalanche was approximately 100 ft wide and 25 ft tall, breaking on facets just above a crust near the ground. The slide was purposefully snowmobile triggered as a test slope on Sunday, 17 December. Slabs of snow were also breaking off as we climbed up next to the avalanche, showing conditions are still primed for a slide (see video).

The December snow is weakening and faceting including on sunny slopes where the Oct/Nov facets are more crusted. Surface hoar is big and widespread.

I dug 3 pits on or around the Ramp which is to the north of Bridger Bowl. One was SE facing, the other was E facing and our last was N facing. Depth ranged from 45 cm to 67 cm and all stability tests (6) had ECTN12-14. We had no collapsing and saw no avalanche activity. The snow structure is poor: weak, sugary facets on an ice crust capped with a foot of snow. Although our observations are showing a trend toward stability, there are still slopes that will avalanche. These slopes would either have more snow or wind-loaded slabs above this layer; in essence, a meatier slab. The only way to know is to dig and test. And if you ski, watch out for rocks!

The road into the Throne was marginally snow-covered. It was good enough to get in on sleds without them overheating, but it may not make it long with above-freezing temperatures. We toured up the shoulder to the north-facing run off the top, digging four pits along the way. We experienced no collapsing or obvious signs of instability deeper than superficial cracking. We found 10-24" of snow on the ground. In many of the thinner areas, the entire snowpack consisted of facets.

We focused on finding areas with a cohesive slab over the facets as our primary concern. We had unstable results in the pit in which we found this recipe (ECTP12), but feeling that there was a lack of connectivity in the slab, we proceeded. In our other pits, we had ECTNs and ECTXs because the entire snowpack consisted of facets. 

From email: "Just sharing a photo I took of some large surface hoar.  This was taken up in carrot basin in a spot that was especially bad, in the shadows sheltered by trees but adjacent to warmer sunny spot.  It didn’t look like this everywhere but it certainly was a common sight."

Went on a ski tour up Lionhead Ridge yesterday (12/18). Noted lots of sled tracks high-marking avalanche terrain on the east side of the ridge, but no major crowns. Saw one small natural crown on a NE rocky outcropping around 8k, 1 foot deep and isolated. Felt a lot less collapsing than last weekend, however still found some instabilities. Notably a remote collapse that propagated around 50’ in length at around 8200’ on a NE aspect.