Snow Observations List

From IG message: "Getting word that a group triggered a decent slide today out at cabin creek. I’ll attach the coordinates to the general area, to the best of my knowledge.

44.86484, -111.22023

No burials. They were able to outride if. But thought I’d send coordinates in case you guys were gonna be in the area and wanted to check it out."

Snowpit attached from an east aspect at 9400', south of Cooke City today.

HS 250 cms, with the Feb. 3rd dust layer about 100cms from the surface.  EXTX.

Below the dust layer there were 1mm rounding facets, that were 1F hard.

No avalanche activity observed, with LOTS of looking around.  No collapsing, no cracking.

Temps around 40F in the valley, but minimal wet loose activity observed so far.  The warmup has been gradual the last 2 days, with good freezes at night.

Also, there was a wolverine up on the mountain this morning!

Riding in this morning, we saw this older wet slide on the Portal Creek road down low at about 6400' in elevation on a south facing slope by lots of exposed rocks. For reference, Gallatin River is 5800' in this area.

We didn't see any fresh ones on our way out at about 2:30. 

The most likely places for big wet slides are slopes or areas with exposed rocks and cliffs. Generally these wet slides happen a little predictably in the afternoon as the snow gets wet. We know what time of day they'll happen, but it's hard to know exactly when they'll release, so watch out when the snow is obviously wet if traveling under slopes like this. 
 

You don't need to worry about them in the morning, when the snow is frozen. What a nasty avalanche with sticks, rocks, and dirt in it?

We toured up to the prayer flags on the Ridge above Beehive Basin, got a good view around the basins, dug to the south of the cornice line there, and descended the south side of Tyler's path. Clear skies, slightly above freezing temperatures, and calm wind. The surface conditions were better than I would have expected, with dry snow/ no crust on all aspects other than those tilted south-facing. The lower elevation snow in the basin was getting wet by the time we departed at 2 PM. I would expect some wet loose avalanches this afternoon. No wind loading or signs of instability observed. 

Our pit showed good stability (ECTX). This fits with the pattern of avalanche activity driven by snowy and windy periods that quickly improves with milder conditions in the mountains around Bozeman and Big Sky. We are optimistic about the nice weather and generally safe conditions coming up this weekend. 

Watch out for these three things and you will be looking good to get into a fair amount of fun terrain this weekend in the Bridger, Northern Madison and Northern Gallatin Ranges, and the Centennial Mountains in Island Park: 

1. Wind-loaded terrain where you could find lingering wind slab instability.
2. Cornices: They are really big currently, and we may see a few breaking off with the warm temperatures this weekend. These can collapse much farther back from the edge than expected. 
3. Wet snow: With forecasts calling for above freezing temperatures under sunny skies, we expect wet loose snow avalanches to slide on sunnier (south and west) aspects. These will generally be small and involve only the recent snow, but they can still injure or buried skiers, riders and climbers in steep terrain or gullies where they can push backcountry travelers into terrain traps (trees, gullies, cliffs, rocks). 

Isolated instability can have significant consequences on larger or committing terrain objectives. Stack the deck in your favor by digging down a few feet and testing the snowpack so you don't get surprised. 

Toured much of the Hyalite zone yesterday.  Winds calmed, sun came out mid day.  1” of new snow and 3” the day before.  Skiing was great.  Saw a couple huge cornices that had broken off.  From the top of Devide peak we observed what looked like a cornice release above the headwaters of storm castle creek which triggered a slab, east facing aspect.  Looked to be several feet deep and ran a long way. No other signs of instability observed.  Great skiing. Solar aspects were saturated by the afternoon.

Been meaning to share some recent obs from a ski trip we took into the Centennials. Overall good skiing, fairly consistent and deep coverage with height of snow ranging from 155cm to 180cm. Skied from 21 Feb to 24 Feb, light new snow on 23 Feb-24 Feb, with strange rime event happening overnight Sunday into Monday. Created a ~2mm rime layer on snow surface on most aspects and all elevations.

There was evidence of other rime events in all pits we dug, thin little ice layers (1-2mm) evenly spaced throughout the upper ~70cm of snow. Significant ice layer in all pits at ~1m from surface, from 4-6mm thick. 

Pit 1, ~7700', ENE aspect, ECT 25 on rime/ice layer ~50cm from surface, Q1

Pit 2, ~8800', W aspect, ECT 23 on rime/ice layer, ~70cm from surface, Q1

Pit 3, ~8900', WSW aspect, ECT 25 on rime/ice layer, ~70 cm from surface, Q1

All failures featured dense, cohesive slab popping right off the column at failure. We kept angles shallow and had good skiing until the rime event, which created a nasty little surface crust. No evidence of old avy activity visible, but we had fairly limited visibility overall.  

Fresh wind slab avalanche seen this afternoon, possibly rider triggered.

We received a call (from a third party) about a snowmobiler that was buried with their head 5 feet below the snow and their foot sticking out of the snow. Their partners saw the foot and dug them out. The riders face was blue, but quickly became responsive after a "chest thump". 

They were riding on the north side of Miller Mtn. Given the widespread winds and drifting, we suspect it was likely a wind slab avalanche similar to one spotted on Crown Butte the same day.

Several inches of dense new snow really made great skiing and riding on top of either an ice crust or firm layer of snow from recent sun and warm temps. 

Winds had moved snow at upper elevations.

Total snow depth on a NE aspect was 230 cm (7.5 ft). Right side up and strong. Dust layer from Feb 4th was 70 cm deep (28 inches) with no facets under it. 

The main avalanche problem seemed to be wind slabs. 

We toured out north of Bridger Bowl and onto the west side of the range, searching for shallow snow and reactive buried weak layers.

While we did find shallower, weaker snow compared to what we've seen on the east side, it is remarkably deep back there! There is close to 5 feet of snow at around 7200'. What was mainly present were layers of weak, faceted snow that formed during the high pressure at the end of January. These were capped with a slab of newer, dense snow. This slab and weak layer combo gave us ECTN's in all our snowpits. An atypical amount of snow exists in this zone, and while an avalanche breaking on this persistent weak layer is unlikely, there may be isolated areas where you may be able to trigger a small avalanche breaking at this interface. 

Apart from looking for weak layers, we were nearly blown off our feet a few times by strong westerly winds. There was significant snow transport occurring at upper elevations and ridgelines. Our ski tracks and snowpit were almost entirely blown in on our return back to Bridger, and we were able to trigger cracking in small, newly-formed wind slabs. With a few more inches of snow forecasted tonight, and continued winds tomorrow, our primary concern will be wind slab avalanches breaking in the upper 1-2' of the snowpack. 

Outside of wind-loaded terrain, natural and human-triggered avalanches are unlikely on non-wind-loaded slopes in the Bridgers. 

We went to look at an avalanche that was triggered two days ago, remotely from flat terrain above a steep slope, on the northeast end of Mt. Abundance. While looking for the avalanche from the flat bench above we triggered a similar sized slide directly adjacent to the previous slide. They broke on weak layers of facets and surface hoar that formed at the end of January. 2-3 feet deep and 150-200' wide. 1F to P- hard slab above the weak layer with 25cm of 4F to F snow at the surface. AFr-HS-R3-D2-O.

We also saw at least 3 rider triggered wind slabs, 4-5 natural wind slab avalanches, and a couple large cornice falls.

Strong wind had affected almost every piece of terrain, scouring some slopes, loading others, just stiffening the slab in many areas, and forming fresh drifts on every convex roll and along the edges of trails. Riding was still soft and fairly consistent in many areas.

I expect wind slab avalanches will be easy to trigger for a day or two more due to how reactive drifts were today... and it is still blowing and snowing a little more tonight.

The persistent slab avalanche problem is tricky because we have not seen any other avalanches of this type near Cooke City and it seems isolated, but slopes that harbor that instability might have just reached a tipping point with this round of wind-loading and dense snow, so it seems possible we could see a couple more of these avalanches over the next couple days or later this season. It will be a good idea to step back from most slopes steeper than 30 degrees during this wind-loading event, especially slopes with larger consequences like trees, cliffs and just generally large steep slopes.

From email: Came out of Hyalite around 1:30 today. There were several small slides to the road in the canyon. One slid all the way to bare ground.

Today I saw a very small wind slab on Republic Peak. Crown was 10 feet wide. No other avalanches observed 

From Text message: “Clean up on aisle hyalite!  Couple small wet slides between the retaining wall and practice rock, big enough to reduce the road to one lane.”

From IG Message/ Stories: “Took a short ride with the recent storm slab yesterday. A good reminder to keep only one rider exposed at a time, and to be ready for anything. Stay safe out there.”

Observed a snowmobile triggered avalanche today. East facing slope, approx 9700', between Fischer Peak and LuLu pass. Rider was not caught. HS-AMu-D1-R1-I. Observed lots of wind transport and loading from strong w/sw winds today. 

8761ft

43 NE

13 degree slope

HST 125

ECTP 12 50 down

Soft snow ski pen 30 cm

supportable pow

clear skis tell 11:20

11:20 few

We went up Republic Creek to look at the stability of snow that has fallen over the last 2-3 weeks. Skies were overcast with light snow falling most of the day and winds were moderate with strong gusts.

We found a thin layer buried 2’ deep that showed potential to propagate and slide. We dug down 4 feet, just below the dirt layer that was deposited earlier this month. We got an ECTP30 that broke about 8" above that dirt layer. This was either on a thin layer of facets or preserved lower density dendrites.

We heard of an avalanche that was triggered yesterday which broke 2’ deep and 250’ wide, possibly on this same layer, on an east facing slope by Mt. Abundance.

The wind was blowing new snow into fresh wind slabs. We were able to easily to trigger a couple wind slab avalanches on test slopes. More snow is expected tonight and tomorrow which will increase the likelihood and size of wind slab avalanches, and the added weight could cause a 2-3’ deep avalanche to break a couple hundred feet wide. Be cautious of steep slopes as new snow and wind build slabs over the next couple days.

We got to ride into Tepee Basin with a pair of snowmobilers who were involved in an avalanche two days ago (2/23). The pair generously offered to join us and run us through the incident. It was an incredible opportunity to learn from each other. Read details about the slide.

The avalanche failed on the weak layer of facets that formed in late January. We also spotted another avalanche in similar, mid-elevation terrain likely triggered yesterday or earlier this morning. Both of these avalanches fit the pattern we've been seeing in Lionhead and the recent slide outside the forecast area in the Black Canyon area of Island Park. Other than the Black Canyon avalanche which is uncertain because we have not visited the site, the slides are taking place in mid-elevation terrain, smaller slopes with minimal wind-loading, and a thinner snowpack. 

The snowpack in both the Tepee slides was thin relative to the average snowpack depth (129 cm). 

Take Homes:

1. You aren't good to go if you avoid the steep, upper-elevation, wind-loaded bowls. Steep slopes at mid-elevations harbor weak snow and have the potential for an avalanche. 
2. The persistent slab avalanche problem is alive and well. The epicenter of this problem is in the Lionhead area and the Southern Madison and Southern Gallatin Ranges. 
3. The issue with this avalanche problem is the distribution. It's nearly impossible to tell which slopes will slide and which ones won't. On many, the weak layer isn't so weak and the likelihood of triggering one is low. On other slopes, the weak layer is very weak and the likelihood of triggering one is up there. 

Rode around the pioneer scenic byway with the motorized avalanche fundamentals course. 

At 8500 SW aspect there was 120cm snow ( see picture for structure) ECTP17, ECTP23 failing on large basal facets/ depth hoar 25cm up from the ground. New snow from February is 1/2 the HS. 

As the afternoon warmed up we saw roller ball, small loose wet avalanches and shooting cracking from snowmobile tracks. At the end of the day we observed a very small avalanche on a road cut, also shooting from a track. 

We did not ride much off trail, where we riding the snowpack was shallow and you could easily punch into the weak snow.