Snow Observations List

Skied Ellis yesterday, good snow but quite busy. Dug a pit at ~8000’, ENE aspect. No failure in ECT with snowpack from 130-140cm. Bit of a crust/layer ~ 30cm below surface on open, exposed slopes but not present in forest. Minor wind impact on top slopes, zero wind impact below ~7800’. 
 

4-6’’ wind slabs cracking on test slopes on W aspects at upper elevations today

Sledded up storm castle. Spent the majority of the day skinning and skiing NE to NW aspects. Found debris from multiple R1-D1 wind slabs from earlier this week. Found widespread but inconsistent wind slabs (2"- 6" thick) at elevations 6700' to 8400'. Throughout the day cracking and collapsing was noticed multiple times on areas of stiffer snow. Snow quality changed dramatically from powder turns to thick wind crust with no visual surface difference.

Recent snowpits attached from mid elevation E, and SE aspects near Cooke City.  

Of note, it appears that the Feb. 3 dust layer, perhaps has become weaker/ more faceted with the recent below 0F temps of the last 4 days.  Will continue to monitor this layer of concern as the weekend storm progresses.

We toured into Specimen Creek today and rode on E-SE and W aspects. Though more snow exists in this location than is typical, the snowpack here is still shallow and weak.

Our snow profile on a W aspect at 8100' showed us some of the weakest snow structure we had seen this season. Sugary, large-grained facets and depth hoar spilled out of the pit wall at the ground. In this location, a 6" slab sits atop this weak snow, but was not cohesive enough to get unstable test results (HS: 90, ECTX). 

Outside of very weak structure, no other signs of instability like cracking, collapsing or recent avalanches were spotted. 

While the state of the snowpack now provides better coverage and riding than usual, expect to see a jump in avalanche danger on these shallow, weak slopes when/if they receive another good round of snowfall. 

We snowmobiled and skiied around the northern bridgers yesterday. Found lots of wind effect. Most faces had been wind scoured, some protected south facing slopes were wind loaded. Noted a few small natural slides, one other group reported to us that they popped a wind slab on a south facing slope. We bailed on our bigger objectives and found some decent snow in a sheltered south facing chute, we did not experience any instability on this but I'm sure on other slopes we would have seen wind slabs. A thicker wind crust was developing in most areas. Snow pack seemed really solid and deep, except near cliffs and hidden rock piles, were we found facets to the ground.

Noticed a large cornice triggered avalanche on Mineral Mtn today. Likely broke on 2/12 or early am 2/13. E aspect ran almost to the valley floor.  Active Loading today with Strong Gusts from N-S. There were some other small cornice avalanches to the north of this slide that did not trigger larger avalanches.

Lots of snow transport above treeline today south of Cooke City. Wind gusts were strong. 

We rode into the Taylor Fork, down into the bottom of Sunlight Basin, across Carrot Basin and to the Wilderness Boundary. We saw four persistent slab avalanches that likely broke last weekend or at the beginning of the week. All appeared to be snowmobiler-triggered R1-2, D1.5-2 avalanches at broke of the January layer of near-surface facets and surface hoar. Additionally, we saw one wind slab avalanche (R1, D1) in Sunlight Basin. This slide was fresh from this morning or yesterday. 

We dug a crown profile for the persistent slab avalanche in Sunlight (attached). ECTN24 on the SH layer buried 50 cm (20") deep.

We also dug above Carrot Basin on a northeast-facing slope: ECTP14 & ECTN15 on the NSF layer 50 cm deep. 

Near the Wilderness Boundary on a southeast-facing slope: ECTX

Persistent slab avalanches still seem possible, but it they have reached an equilibrium on most slopes that feels like the bottom end of MODERATE danger. Wind slab avalanches are certainly possible with the fresh slide as evidence as well are shooting crack in a drift as we rode in. Outside of large terrain, these will not be that large. 

New snow and increasing wind starting tonight will change the equation. The snowpack can take 0.5" of SWE without notching up the danger, but 0.75" with more coming would make human-triggered avalanches likely. 

Triggered a small wind slab avalanche on the east face of mt Blackmore today at 9850 ft elevation. Around 5 inches thick, ~ 20 ft wide, and ran for 100 ft. No skiers were caught but the slab was very reactive. We were assessing the snow as we climbed but skied a slightly more eastern aspect than we were planning and it was more reactive than expected. Strong winds gusting all day, no active transport observed but obvious that the wind slabs have not settled. 

Climbed in the Mummy II area in Hyalite today. West facing ~7,500'. Lots of spindrift coming down onto the climbs in the area and we noticed lots of snow blowing around up high. No snow fell while we were there but our trail in was almost fully filled in and covered with a few inches to a couple feet of wind slab on the way out. Saw a small natural slide that started at the bottom of Cyptorchid. Crown was 10' wide and 8-18" deep, it ran 150' down a very shallow slope and covered the climbers trail. 

Climbing at the Unnamed Wall in the vicinity of The Fat One, there are some 3"–8" wind slabs formed. At least three small pockets had released from 2" to 5" deep. Lots of spindrift and heavy winds filled in parts of our trail in a few minutes.

On a cold day we rode to Frazier Basin and quickly answered the question, “Are wind slab avalanches still possible or have they stabilized?” We saw a natural avalanche (R2, D1.5) that released on a steep headwall just to the south (I believe I’ve heard this referred to as October Bowl). 
 

Wind has affected most of the snow above forested terrain in some fashion. While most soft snow has already been redistributed, some transport continued. We looked at skiing Thing Two but the wind slab problem and poor skiing quality deterred us. I did dig a pit with an ECTP11 breaking 5” down below the slab. Surfaces had hardened and I suspect terrain would have to be pretty steep for an avalanche to release (this type of steep terrain is abundant in Frazier). 
 

We departed Frazier area without skiing and went to look at lower elevation terrain above the Carroll Creek Road. The wind had gotten to the snow here as well but no signs of instability and an ECTN15 18” deep. Triggering an avalanche outside of wind loaded terrain is unlikely. 

Toured up around Blackmore and s cottonwood. Found an extremely reactive windslab in the afternoon. It was thin, but easily triggered and would propagate about the width of each terrain feature (20-50ft). Each slab ran the length of the slope (150-200 ft). 

From FB message: "Small slide in lower elevation back by lionshead"

Cold temps and sunny days starting to create some surface hoar forming seen on the primary ridge of big Ellis. Surface hoar was less widely distributed on the primary ski zone but was present all along the top of the ridge. 

Explored slopes in lower Hyalite Canyon between 6000-7000 ft in elevation. Really close to being skiable and good. Otherwise, we found snow depths ranging from 6 inches to 2 feet. Generally very weak and faceted with thick crusts on slopes with a southerly tilt. All this weak snow probably won't be an issue because this area only gets the scraps from storms and never has enough loading to make an avalanche problem. 

Dug a pit and did an ECT near the NE entrance to Yellowstone. I dug at 9500ft, W aspect, on a 29 degree slope. HS 275cm. I got an ECTP12 55cm down, right above the obvious layer of dirt. Moderate winds from the west. 

Moderate winds today north of Cooke City. Stronger winds than forecasted and lots of snow is being transported. Couple hand pits showed planar breaks on a crust on SW aspect around 9600 ft. 

Went into the beehive area today to do a bigger jaunt into the alpine and make it around the basins. Dug at 9200’ on an E aspect on the Beehive/Middle ridge and ripped two ECTs. First test result was ECTN12 on the dust layer. Second test yielded an ECTX. We went ahead with our plan to ski some fairly steep terrain throughout the basins, taking it slow, and making surface and visual observations throughout our day confirming our plan. Most of the surface snow was minimally wind affected and skied great. We saw only small sluffs on anything we could see (no slab avalanches). There was some small shooting cracks while setting skinners, but nothing especially concerning. There was evidence of a stubborn older wind slab underneath the newest snow on one of our lines. Overall, great day!