Snow Observations List

Iv been fortunate enough to spend the past three days skiing around hyalite. On Monday, we were skiing a low angle gully a mile NE of Backmore along the ridge. We noticed new snow point and releases on most steep aspects above 40 degrees, no signs of new snow stuff stepping down. Today while on the East Fork ridge south of Palisades mountain, I covered SE-NW aspects and the new snow seemed well bonded. Solar aspects from the high pressure last week had an obvious crust layer, but new snow seemed bonded. On shadier aspects, I felt facets below new snow but no obvious signs of instability.. yet. 

Summited Mt. Blackmore 12/10. High wind and heavy wind loading were found, but minimal signs of instability were found within the wind-loaded areas. Some localized cracking and collapsing were observed throughout the boot pack but had minimal propagation. Before the climb, we performed an ECT on a wind loaded slope and found inconclusive results with ECTX. 

We skied near Lulu Pass and dug a pit on a northeast facing slope at 9,500'. There was 6-8" of low density new snow on top of a thick layer of surface hoar (10-16mm, photos attached). Snow depth was 90cm. There was a layer of small facets directly below the surface hoar, and below that the snowpack mostly had rounded grains and showed little signs of weakness. We had an ECTN12 on the surface hoar layer. While skiing I saw some 5 foot long cracks across the snow surface on a wind-affected convexity.

I'm not sure how widespread the buried surface hoar is, but this will be our primary interface of concern when we get more snow. We did not find surface hoar on south and west facing terrain in this area, but there was a crust with small facets below it buried 6" deep. Right now there is not quite enough recent new snow to create widespread instability. I do suspect a slab of drifted snow or a wind stiffened slab could propagate easily, especially if it lies on buried surface hoar.

Light snow fell most of the day with maybe an inch of accumulation all day. Wind was light and temps were single digits to low teens. Some moderate gusts in the afternoon, and winds increasing in town this evening. 

We rode out of the Buttermilk Trailhead to the old Ski Hill at Lionhead with Gallatin County SAR, Fremont County SAR, and local snowmobile guide from West Yellowstone for our annual West Yellowstone Avalanche Fundamentals class.

It snowed lightly all day without much accumulation (maybe an inch). Winds were stronger than I anticipated, but weren't moving much snow at 8000.' I suspect there was a bit more transport at higher elevations along the ridgeline, but there just isn't much soft snow available for transport. Isolated instability is tied to wind loading. At the Ski Hill breakover, we dug 40 people worth of snow pits. In a couple of them, there was just enough wind loading to get propagating results (ECT16-ECTP24) on basal weak layers. 

Recently, buried surface hoar and near surface facets didn't have enough new snow on it to cause problems, but it was preserved under 1-2" of snow. 

Skied from Beehive into Middle Basin today. On NE-E aspects there was ~25cm of low density snow over a supportive midpack. On SW-W aspects there was 5-15 cm low density snow over a supportive crust. Moderate NW winds were moving snow, but wind slab formation where we travelled was isolated to immediate ridgetop easterly aspects.

We toured up to Mt Blackmore today to assess how the snowpack is reacting to the recent snowfall. We traveled into the bowl and up the SE face to the ridge. Strong winds were noted off of ridgetops, as well as at lower elevations, before popping out into the bowl. But the SE face below the ridge was remarkably less wind effected than we expected.

The good news: Hyalite was the clear winner from our last storm cycle, and we noted around 15 inches of new snow at 9700'. The bad news: in our snowpit, we got an unstable test result of ECTP 13 on a crust - facet sandwich below the new snow. Unfortunately, the snow that makes up the base of our snowpack is made up of several old crusts and facets.

Where we traveled, we did not note much wind slab formation. Beyond our unstable test result, we did not note any other signs of instability - no recent avalanches or cracking/collapsing beneath our skis. 

Went north of Bridger Bowl towards Texas Meadows. 

Winds - blowing strong at the ridge and below about 7400 feet below most of the avalanche terrain (Top of the Alpine Lift down to the BB base area). Winds not doing much around the elevation of the Bridger Lift and the Ramp.

Snow - Just creamy, supportable skiing. South aspects have a supportable melt-freeze crust keeping you off the ground. North aspect have supportable snow. More wind affected areas had alternating scoured snow and wind-deposited snow, but skied pretty well. 

Avalanche issues - All tied to the wind. Fresh drifts were easy to find where the wind was blowing. Avoid wind effect and ski/ride soft snow and you avoid avalanches. The old snow surface faceted but not too badly compared to other areas. I suspect you could find areas where the old snow surface was more faceted and weaker, but they seem isolated. 

Light winds below treeline had little to effect on the snow in the history rock meadows. It was clearly blowing up high, with exposed nw faces stripped of snow and active transport visible off of Blackmore.

Skied up through Maid of the Mist Basin into Twin Falls Basin, attempted to boot up the Pinner but was foiled by too much snow. Very strong (almost blew one of my skis away) wind on ridge lines transporting significant amounts of snow. Despite this snow seemed very stable, small wind/storm slab not very consolidated breaking, but not propagating. Skied all sorts of aspects and all angles and saw few signs of instability. Day before friend observed 6-8ft shooting cracks when walking across >30 degree north-eastern aspects near try line, will try to get him to submit video, skied same slope and was unable to replicate a day later. Absurdly deep conditions high up in Hyalite, some of the better turns of my life, hopeful the storm bonds well with previous snow.

Skied Candyland near Shower Falls in Hyalite today. Got a decent look around and didn't see any natural avalanches. Got a ECTN12 @ 8k' east facing aspect at Candyland. Fractured at the new snow old snow interface about 40cm down from the surface. 115cm total snow depth. Very soft upper 40cm of snow with firmer snow underneath. Was snowing on and off while I was there and still snowing when I left

Just an initial look at low elevation snow around some of the ice climbs.

8" of new snow at the Grotto Falls TH. 
 

I couldn't find any surface hoar that was buried by last night's snow, but I'm sure it's out there. Doesn't really matter because there's plenty of weak, faceted snow that was the previous snow surface.

The new snow is all fluff and not a concern at lower elevations in Hyalite. Perhaps it could be enough of a load and enough of a cohesive slab at higher elevations where more snow fell. 

For now, things seem mostly stable, but that will change quickly with any amount of wind. 

The snowpack remains thin in Island Park. We rode the Big Springs Loop around the Black Canyon area in Island Park. We dug two pits near the top of the loop in the area where one crosses the Canyon. One was on a southwest facing slope and the other on a north-facing slope. Both near 8100' elevation. 

The snow depth was 60-70 cm (2-2.5 feet). Surface hoar and near surface facets are now capped by this weekend's snow. The layers are buried 2-4" deep. These are not a concern currently but certainly will become so with the next significant storm (or incremental loading). ECTN2-4 on these layer for now. Winds were calm and avalanches in non-wind-loaded terrain are unlikely. Small areas of isolated instability are possible in higher elevation wind-loaded terrain. 

Noticed this natural avalanche on 12/8. East facing slope, ~9500 feet, Hayden Creek above Ripcurl area 

With another day of high pressure and clear skies, Alex and I rode into Lionhead and parked the snowmobiles at the top of Ski Hill. The coverage in and out was decent for this time of year, but thin cover and sharks abound. We dug a snowpit at the top of Ski Hill (8150')  and then toured up to the south end of Lionhead Ridge and dug there (8650').

Our snowpits told very similar stories of a weak, layered snowpack from top to bottom: glittering surface hoar on top and different variations of facets to the base. In both snowpits we got ECTN's on interfaces between faceting snow. In our upper pit, we noted a more cohesive slab on top, but it was just not enough to get propagation in that spot. 

As we skinned up the ridge, we also noted very isolated collapses, one to two feet from the tips of our skis. But overall, there were no signs of instability, just weak snow, growing weaker by the day. 

Until the next round of snowfall, our main hazards continue to be the rocks, trees, and stumps just beneath the surface.  

We skied around Scotch Bonnet and Sheep Mtn., north of Cooke City today.

No collapsing nor cracking, nor any avalanche activity observed.

Snow profile attached from a SE aspect at 10,000' on Scotch Bonnet.  HS65, ECTP22 @25.

Surface hoar (4-8mm), observed on most slopes, except on steep solar slopes and especially windy locations.

Today, Ian and I rode Buck Ridge. The trail in and out was in decent shape with a few wind-stripped bare spots but mostly continuous coverage. We got eyes on First, Second and Third Yellow Mules as well as into McAtee Basin. Small, glittering surface hoar covered most aspects. At the head of Second Yellow Mule, we dug a pit on a NE aspect at 9400 ft and found a snowpack with weak layers throughout: surface hoar and near-surface faceting at the top and faceted snow near the ground. We got an ECTPX as we just didn't have the load on top of these weak layers to cause slab formation or propagation. 

In general, we did not see any notable dry-snow avalanche activity or signs of instability. Despite sunny skies, the snow surfaces we rode on stayed dry. One small loose-wet avalanche on a S facing aspect on Eglise Rock was observed that likely broke in the last day or two. We also noted a few reported wind slabs that broke last week. 

Our main hazards today were the early-season coverage and buried obstacles. 

We rode into the Taylor Fork to the weather station and then over to the wilderness boundary. The trail in and out was in decent shape. The riding in the Taylor Fork was very thin with plenty of barely hidden obstacles. We moved slowly through the terrain and managed to avoid the landmines. 

It was 12 degrees when we left the car, temps were warmer up as we climbed but, even under sunny skies, the snow surface never got wet. Dry snow conditions were mostly stable, with no wet snow instability. I would worry about hitting a buried log or rock more than triggering an avalanche. However, we did get a couple of propagating tests in a 60 cm deep snowpit at the edge of Sunlight Basin (ECTP18 @ 22 cm) and at the Wilderness Boundary in a 49 cm deep pit (ECTP14 @14 cm). 

The snowpack is getting worked by the period of high pressure... surface hoar and near surface facets up top and faceting at the base. We will continue to monitor the state of the snowpack as we move toward the next snowfall assessing the structure that will eventually get loaded. 

This was a nice walk to stretch the legs in the Taylor Fork. My observations largely aligned with what GNFAC fxers observed in the same drainage on the same day.

Deep temperature inversion was present, it was 3 F when I left the car at 10 in the morning, and I eventually climbed out of the cold pool of air around 8,200'. I stopped and dug a few roadside handpits on the drive in from 191, it was impressive how much additional faceting was occurring below the level of the inversion. Here, the snowpack consisted mostly of 20-30cm of facets (DH near ground), with a decomposing 4F ambient temp crust in the mid-pack. I had no stability concerns down low today, but this very weak lower-elevation snow will create problems with additional loading. With enough load I would expect to see frequent, long-running collapses as well as the potential for remotely triggering slides from long distances in valley bottom locations. Many low elevation slopes facing SSE-S-SW-WSW had lost much of their snow cover, but solar margins and anything tilted a bit away from the sun were holding snow.

Above the level of the inversion and continuing up into the alpine the snowpack looked a bit better, but not great. Faceting was less pronounced and I was unable to get ECTs to propagate in a pit dug in a relatively flat meadow at ~8,600' (which felt like a decent proxy for shaded slopes based on structure). However, shortly after leaving this pit I initiated a large collapse that traveled across an entire large meadow; the collapse was audible for over a second as it propagated. This collapse and the weak layer of concern in my pit is the widespread basal weak layer, buried beginning in mid-November. This was the only direct instability feedback from the snowpack I experienced this day.

In the alpine, snow surfaces were weathered and highly variable, presenting as a mish-mash of facets, crusts, thin wind skins, and stiffer, denser hard slabs from recent snowfall. None of these surfaces looked terrible, but I'd expect a quick load of snow+wind to find plenty of locations with collapsible weak layers capable of producing avalanches. I looked around for a place to dig and look at basal weakness but was unable to find anything of value due to this high degree of variability. There was a thin but widespread rime/humidity crust in the upper few cms of the snowpack that was present as high as I observed (11,000' +). I observed some cracking that had occurred previously in steep, heavily wind-loaded north-facing terrain. It was not perfectly clear if this cracking involved the weak layer near the ground or just the thinner, wind-drifted hard slab near the surface, but it seemed like it was more of a surficial problem. 

Lots of surface hoar. Those crystals are often destroyed before being buried, but surface hoar is a good sign of weather conditions that are good for near surface faceting.

The upper few inches of snow is a mix of broken snowflakes that are starting to facet a little bit. Not too terrible yet.

Deeper layers of old November snow closer to the ground are faceted and breaking in stability tests. To get an avalanche breaking on those facets, I think you need an old wind slab on top. Even then, I think the sensitivity has dropped a lot. 

We did see one recent wet loose avalanche that started near some exposed rocks in a place that typically gets wet. I did NOT see any wet loose slides in East and Southeast-facing gullies on Barronette peak. However, I'd be nervous ice climbing in these gullies when the sun is hitting them.

The snow Ranger Crew got out and about on Buck Ridge today.  Trail in was in OK shape but is likely to melt back and get worn down over the next few days from sun and sled traffic.  Riding started to get quite good above about MM7; snow was generally supportable and ranged from 50-85cm deep for the most part.  Open areas had some wind effect but there were few hard drifts/slabs.  Anywhere that was sheltered from the wind had a layer of surface hoar forming, not surprisingly.  The head of Beaver Creek was scoured nearly to dirt and the cornice is quite large there already.  We noted one small wind slab avalanche just below it.  We found a similar avalanche in Second Yellowmule that again appeared to be from wind loading.  Both appeared to be several days old.  We dug a quick pit on a north facing slope in Second Yellowmule and had an ECTN in 85cm of snow.  Only the bottom 5cm or so of that pit were sugary and faceted.