Snow Observations List

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. 

Up at G2 on Sunday (2/23) small wet sloughs were coming down to the left & right of the climb all day. A couple bigger wet slides had totally taken out sections of the bootpack approach from G2 to Hangover. Saw big pinwheels and sticky snow all day. Most stuff available to slough probably fell already but stay alert up there.

A rider triggered a slide on Saturday (2/22) on a bench below the east face of Mt. Abundance... Trigger point was from the top while driving by. 2' deep, 250' wide??

Found moist snow that was starting to freeze on solar's in Hyalite at 8000' Friday. Went searching for better conditions up Specimen Creek today. The snow quality was much better at similar aspects and elevations. Northerly aspects stayed dry in both zones but I was curious about the difference in the two advisory areas. Looking at temps from weather stations the southern range has been 10f to 15f degrees cooler. 

Stability was much different as well. In Hyalite, the nsf layer that was formed in late January, looked to be rounding and didn't produce propagating results or clean shears. Up Specimen I had an ECTP15 and a CT15 Q1 on the same layer. This certainly aligns with the forecast. 

On a ridge up Specimen, winds were moderate from the SW and shifted SE in the evening. I did find thin reactive wind slabs and cracking in fresh drifts. Wind was actively transporting on the ridge. I felt wind loaded slopes had the greatest potential to slide since sheltered slopes only had a 25cm slab over the weak layer but I  avoided avalanche terrain regardless. 

Saw a recent cornice triggered wind slab off of Hardscrabble Peak, crown looked fairly fresh. There was a second crown line below the rock band. Conditions were very windy, with snow still being transported. Most snow surfaces were wind affected, but saw no cracking or collapsing. 

We skied in Maid of the Mist basin today. Solars had a sun crust preventing much snow from drifting, although the constant moderate winds out of the west were trying their best. We found multiple windslab pockets in the Fat and Skinny Maid, though these seemed fairly stubborn and were not propagating. Found some well developed (4-5 mm) basal facets in the talus of the Skinny Maid as well, and although we saw no signs of instability on this layer they are something to watch out for in steep thin terrain.

No recent avalanche activity visible except some loose wets and small cornice fall from the prior warm sunny days.

Can confirm, it was blowing in the Bridgers.  Up high it was still cool enough that a fair amount of snow was moving around, especially further north.  Clouds of snow were coming off of the ridges and moving through the bowls near Fairy Lake and Fraiser divide.  Around the of the Throne and in the mid elevations we found better, more sheltered snow conditions.  The area around Ross Peak was very scoured.  We saw a handful of small point releases on steep south slopes, likely from Friday, but no other recent avalanche activity.  By mid-day/early afternoon, the snow lower down in the woods was getting pretty heavy and wet and anywhere with the slightest bit of sun exposure was developing a crust.  Talked to a few skiers who toured in the Naya Nuki area, and they described variable snow and very windy conditions.