Snow Observations List

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. 

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. 

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. 

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.  

From email: "Skied into Sheep Creek yesterday. (12/14)

Warm and sunny day.  Above freezing temps at 9500' on solar slopes.  Crusts forming.  Lots of Surface hoar otherwise.

Noted one recent large slab avalanche on a SE aspect of Miller Ridge.  Estimated to be about 100' wide and 1-4' deep.  It ran about 1/3 track or 600' vert.  No fresh snow on the debris, so it likely ran at the end of the last snowfall event.

Less collapsing up there yesterday than what we've been experiencing all week, but there was one BIG collapse in one of the meadows in the valley bottom (estimated 300'+ diameter).  Remote triggers are still a serious concern.

Snowpit from a S, SE aspect around 9300'.  HS: 95, ECTP29 at 46."

9700’, W, 23 degrees, Hs 100cm 

Ectp16 @60cm  on .5-1.5mm facets 

The average snow depth was around 70cm with slab depth being 25-40 cm. Widespread surface hoar on the surface, all elevations and aspects. 

I didn’t feel any collapsing or see any cracking. 

Today I was skiing a south facing slope between 8500-9500 ft near Mt Henderson. I observed at least ten large collapses, some of which sent cracks 30 feet long. This slope had a shallow snowpack relative to the rest of the area. 

Lots of collapsing today near Miller Ridge (S, SE facing slopes), just 50' from the road. This continued in more sheltered areas as well. Dug on a NE facing slope at 9300', HS: 80 ECTP12 @ 40 cm. 

Observed a fresh slab avalanche on Mt. Henderson this morning.  E, SE aspect, 9,900'.

I skied up to  investigate it and would estimate the size of the crown to be 2-4' deep and about 80' wide. Somewhat surprised by the size relative to the starting zone. Likely a natural avalanche (from about 36 hrs ago), but there were fresh sled tracks in the vicinity from yesterday, so possibly a remote trigger.  

LOTs of collapsing again today while breaking trail on low angled S, E and W aspects.  Some collapses were quite large (100'+ diameter).

Observed this natural avalanche on the south summit of Mt Henderson. Slope is SE facing, 9800 ft. This slope is heavily wind loaded. I estimate the crown is two feet deep and the avalanche is D2. Likely occurred on Friday 12/8 

From email: 

"We skied in Republic Creek and Hayden Creek today.

No avalanche activity observed, but we had very widespread collapsing (about 20 large thunderous ones), on all aspects, primarily in the upper elevations.

Snowpit attached from a west aspect at 9700'.  HS: 90.  ECTP3 @ 54."

From email: 

"South of Cooke City today. Good conditions on low-angle open meadows. Fun problem-solving in the trees!

MC/PC/PS/C, seasonal temp (20s), calm.

No collapses or shooting cracks. Corners broke on steeper kick turns. I had a good view of lower (N) Woody Ridge and did not observe any Avalanche activity. I don't trust this shallow snowpack, but really fun low-angle meadow skipping.

HS 74cm; ECTN14 on new-snow M/F interface, ECTP21 on old-snow depth hoar interface."

We rode up Daisy Pass road and dug below the road at 9,510' on a WSW aspect. Snowpack was 2.5feet deep (87cm). The recent snow was 1 foot =1.6" SWE (measured in field), sitting on a hard crust above 2mm facets which made up the bottom half of the snowpack. We got an ECTP11. We dug a second pit near Lulu Pass on a NE facing slope at 9,520', and found a very similar snowpack structure, without the crust below the recent snow, and also got ECTP11 as well as some ECTNs.

We saw a couple 8-10" deep natural avalanches on the steep slopes above Miller Creek that probably ran in the last 24-48hours. We had multiple collapses on the NE facing slope where we ski toured to dig our second pit.

Constant red flags on W Henderson. 

Skied south of Cooke City today.  LOTS of collapsing and cracking. (maybe 30 good collapses throughout the day)  Felt confident that one could have easily triggered an avalanche today if they wanted to.  

New snow:  about 10cms more last night.  Warmer temps, so the new snow was slightly upside down from the weekend's fresh snow.

ECTP2 on a west aspect at 9200'.  Snowpit attached.  

New/ old snow interface is the layer of primary concern.  (persistent slab problem)

No avalanche activity observed.  

Lots of cracking and collapsing on skin track and ski cuts were reactive on steeper slopes. Dug on NE slope 9640'. HS 110cm ECTN 12 & ECTN 14 40cm down.  

I skied the E. facing meadows above the Erma Mine. 15 -20 cm new snow in meadows.

Cloudy and cool teens F. calm.

Good skinning/skiing on supportable m/f crust below new snow. This layer was quite reactive with cracking/sliding on steep side gully features.

Skied around Mt. Henderson today. Was finding around 28-35 cm of new snow at 9k'. Perhaps 10cms in town. Light density.  Minor wind effect. Partly cloudy morning, turning mostly cloudy. Cold temps. Calm to light winds where I was, but lots of snow was being transported off the exposed ridgelines south of town. Quite a bit of cracking of the new snow this morning while breaking trail and while skiing, even though the wind effect was still Fist hardness.  A couple of collapses noted as well in the deeper drifts.