Snow Observations List

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. 

Rode up from Red Rock road to the backside of Two Top during an AIARE 1 course to evaluate snowpack. At point +044.622746 deg / - 111.247437 deg facing N82E at 8180 ft elevation on a 20 deg slope angle we found a wind loaded slope with 118 cm deep.

Hand hardness 
From 
0 - 15 cm - Fist 
15-38 cm - 1 finger with rounds at .5 mm
38-40 cm - pencil melt freeze layer 
40 - 50 cm - 4 finger with an ETCP - 23 was observed breaking at this layer in the snowpack 
50 - 79 cm - 1 finger with rounds at .5 mm 
79-80 cm - Pencil melt freeze later 
80-94 cm - 4 finger a CTM - SC was observed at this layer 
94 - 118 cm - 1 finger with deep facets and visible surface hoar 

ECTN x 5 and ECP x 1, down 45 (shallower spot as compared to the other 5). PST 30/100 SF, 60/100 end down 58. PST 40/100 end down 55. Two large whumpfs nearby. All obs were at 8700', W aspect (meadow between gem chute and next chute to the South). 

Yesterday I dug a pit just for fun on the backside of Bradley's (7800 ft, NW asp). I found about 30cm of mixed forms (facets, rounds, and grains in-between) overlying 5cm of facets (2-3mm), over a 15cm thick melt-freeze-crust/facet complex. Some of the facets were starting to look like depth hoar.

I got a non-propagating result (ECTN22 down 30cm on the facet layer), followed by a propagating result (ECTP23 down 30cm on the facet layer) in the same pit. This was a good reminder about spatial variability even on a small scale.

Pole probing around the area there were places I could feel the facet layer, and places where the lowermost part of the snowpack felt more like a solid crust. This pattern seemed aspect dependent (crust-dominant on steeper solar-ish aspects, facets in shaded areas or north aspects), but I didn't poke around enough to know for sure. 

Today we rode out north of Cooke City towards Lulu Pass. We dug on a northeast-facing slope at 9600' below Fisher Peak with a depth of ~3' (HS = 88 cm). We had ECTP 21, twice, and PST 67/100 END results on weak-faceted snow above a stout crust. It was easy to find surface hoar in most places on this slope. We then traveled to a southern-facing slope where while ascending widespread whumpfing and cracking were heard and seen. At 9600' a very large whumpf was felt. Here we dug another snowpit with a shallower depth of ~2.5' (HS = 74 cm). Results were an ECTP 11, twice, and a PST 20/100 END. These results were again on weak-faceted snow above the same stout crust. 

Skier triggered avalanche at Lionhead on NNE, 8600 ft. Video of remote triggering slide on IG

Poor test score near Bradley Meadow on an E aspect, at around 7600', during a Friends course. Height of snow was 65-70 cm, results were a sensitive ECTP 3 on the old facets. 

I skied off the backside of Bradley's with the intention of touring up and skiing those north facing shots off of Texas toward the playground. Skinning across the flat meadow below the cliffs heading toward Texas I got several thundering whumphs. I usually feel pretty comfortable on a Moderate day skinning up that notch and giving the overhead hazard as much birth as possible. But, it felt like remote triggers were a real possibility and I was by myself, so I decided not to test my hypothesis that I could set a low exposure skin track and spun back to the top of Bradley's. I was thinking of that observation from a few years back where the solo tourer skinned up those cones to the skinners left and triggered a slide that tickled the traditional skin track. I didn't get any collapses on other slopes, just skinning across that flat meadow. Coverage was as thin as you would expect. There were some steep tracks down Wolverine and off the side of Ramp that didn't produce any action.

We skied two west-facing slopes and one east-facing slope between 8,500 - 9,200ft. on the shoulders of Beehive Basin Sunday morning. The ice crust interface in the lower-middle snowpack seems to sit between two layers of rather incohesive, sugary snow. We did not get results on several hand shears which is thought to be because of the lack of a slab above the ice crust in the snowpack. 

One pocket in a glade of one of our lines had a short shooting crack ahead of my skis as I set our skintrack. ~1ft. of snow propagated uphill onto my skis. With further examination (pictures), it seems that the slab in this pocket, located in a small northwest-facing aspect was more cohesive than other slopes skied today. 

We did not see any other signs of instability during our tour. One natural, likely old avalanche was observed closer to Beehive Peak, on the east-facing steep section of Beehive Basin's west shoulder. 

Went touring with the intention of skiing the main Texas Meadow S. face. Heard numerous loud whumphs while skinning across the meadow below the face. Decided to not ski and dig a pit on a similar south-facing slope. Results were a CT15 Q2. On the way back up to Bradley's had several smaller collapses but none as large and widespread as those observed in the meadow. Plenty of large surface hoar crystals on my way in too.

Traveled Hayden and Republic Creek last two days. Surface hoar throughout all elevations and aspects including ridge tops. Generally large crystal size. 
 

Some settling, no whomphing observed. Old slab avalanche on west Republic Ridge nearing Republic pass. Snow pit off Woody Ridge on SE aspect towards Hayden found ~80cm snow depth  at 9800’ with supportive upper snowpack (4f) above weak facets to ground. ECTP16 with propagation on this interface. Ski quality good. Southern aspects developed a thin solar crust through the wknd. 

From email: "Miller Ridge snowpit from today:  9300', NE Aspect.  HS: 67cms.  ECTP 11 at 36.  

Then we toured over for some runs on SW Henderson.  Obviously more supportable over there.  Less collapsing.

Aside from the widespread SH that has been forming on all aspects and elevations this week, the shady aspects appear to be getting more faceted mid-snowpack, while the solar aspects appear to be gaining strength"

Republic creek tour snowpack observations: 

Observed collapsing/cracking in lower Midway meadows.  Snowpit tests produced unstable results - easy propagation and failure between old snow (Oct-Nov) and new snow (early December).  

Noted one old natural avalanche on south Woody Ridge, west aspect ~9500'.  

Significant surface hoar growth in Republic creek.