Snow Observations List

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.  

Height of Snow from 50-65. Traveled around Bradley Meadow area and down into Wolverine Basin. ECTP 19 @35 cm down (unstable result) 7500 ft east aspect. Experienced a large collapse below the N half of Bradley Meadows in a small meadow - 7400 ft east aspect.

Widespread wumfing between 7,000 - 8,700ft. in Targhee Creek. (12/15)

No natural slides observed.

Crazy large surface hoar also observed on open, southerly clearings, measured 1+ cm. Very rotten snowpack otherwise.

Big Sky Ski Patrol reported two natural avalanches, seen today (12/15) in closed terrain. 

From email: 

"It looks possible that they released at two different times during the day today.....It looks to be the storm snow, which was sitting on lower-density snow at the old snow interface. That interface likely had a layer of faceted snow on top of the old, crusty snow. "

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. 

We rode up Denny Creek towards Watkins Creek and spent the day below the ridge where we saw two natural avalanches. These avalanches broke 12-18" deep on weak faceted snow above a stiff crust. The first avalanche presumably happened sometime near the end of the last storm cycle (12/11), as it had a few inches of snow on the debris. The second was more recent, in the last 24-36 hours. Both were at 8500' and were on NE and E-facing slopes. 

We dug two snow pits near these avalanches and saw propagation in both on a layer of weak sugary snow buried about a foot deep (ECTP13 & ECTP12). Across the area surface hoar was easy to find on the snow surface. 

Performed two ECTs and a PST on an E aspect at roughly 9000’. HS was about 50 cm and the old faceted snow below the new snow was obvious. We had two ECTX in adjacent pits and a PST result of 40/100 Arr on the interface of old and new snow. These results were surprising as the snowpack structure had 4/5 lemons and we experienced Whumpfing on the same slope just 100 feet away. We also experienced whumpfs in other locations throughout the basin.

Toured up to the lake and dug at 9200ft west facing just up slope from the lake. Failure while trying to isolate the column for a etc on fist attempt.  2nd test was etcp1. Some collapsing while skiing across the flats. Three days ago in middle, had some huge surface hoar as well as big collapsing and 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. 

We drove and then rode up Little Bear this morning on the 3138 road (also snowmobile route #900).  Once 3138 splits off from 980 there was mostly enough snow for riding on the road without issues but little else.  Snow depth varied from 4-6 inches, down to 2-3 inches in sun and wind exposed areas, to as much as 18 inches or so higher up (8400').  We also saw some spectacular surface hoar- probably 1-2" tall in places with extremely sugary snow underneath; often so sugary we weren't leaving well defined tracks behind our sleds.  As with everywhere else, we heard some collapses while off of our machines.