Snow Observations List

From instagram: Skier triggered windslab on Scotch bonnet near Cooke City. Approximately 75 ft wide.

Skinner triggered slide north of the hourglass. Run name unknown. Remotely triggered from ridge line; snowboarder said he was skinning 35 feet away from trigger point; no one buried. I also observed point releases as I was skinning up to texas meadows; snow seemed to change quickly under blue skies and increasing temperature. Slide ran in front of me, taking out the skin track. 

Overall seemed like a deep HS (220 cm) versus other years I’ve seen here. High strength in pit (ECTP26), failure on facets below melt-freeze crust down 60 cm, and with no more obvious signs of instability. Felt weak snow deeper, but only dug in the top meter. North winds increasing throughout the day and any wind affected snow was shallow in depth. South aspects were crusted but protected N-facing or tree skiing was still great.

We rode into Lionhead Ridge to pull the weather station for the season. There was a large natural avalanche that broke yesterday on Bald Peak it was bounded laterally by the terrain, so it only broke a couple of hundred feet across, but it appeared to be 4-6' deep and ran the full available vertical into the creek below. This avalanche was the key piece of information for the day and answered the question of whether or not the snowpack is continuing to produce deep slab avalanches with every storm, it is. 

After dealing with the weather station, we rode around to Denny Creek and up under LH Ridge. We saw three more avalanches that broke at least a few feet deep and several storm slab avalanches that failed within the new and wind-drifted snow. No other observed avalanches were as large as the one on Bald Peak. 

We stayed in terrain less than 30 degrees steep, with minor exceptions on small slopes. We avoided all large, wind-loaded slopes and crossed below them cautiously. The snowpack maintains the characteristics of mid-winter, and deeply buried persistent weak layers remain a concern. Going forward, we will continue to assess the upper few feet of the snowpack for instability before considering any steep slopes. We will continue to manage the deep slab avalanche problem through avoidance (of avalanche terrain) and consequence minimization (by selecting non-wind-loaded slopes that are smaller and free of terrain traps). 

From IG: “Wanted to touch base about an avalanche we triggered on the shoulder of Mineral Mountain today. While skinning up there was obvious wind loading coming from the south. I kicked around a bit near the edge of the ridge (no cornice) and remote triggered this slide from 20’ away. It broke 12-18” deep, and propagated 700-800’ wide. Ran full length of the slope into old growth trees 1200’ below. Would estimate R4 D3. We found good stable skiing on the south aspect (~35°)”

From email: "Observed very limited terrain due to vis. Saw this very large avalanche on Climax. The crown looks fresh, so it likely occurred the day or night of 4/1?
Hard to tell but the crown looks to be about 4-6’ deep at its deepest. The debris ran to the creek.
E aspect at 10000’.

There were also several smaller soft slab avalanches that ran on the lookers right side of Climax.

On 4/1 we had a large collapse on a SE aspect at 9800’ where the MF crust was present under 60cm of new snow.

Winds were L-M with consistent gusts to S on Saturday."

From Email:

"Observed a fresh natural avalanche this afternoon on Woody Ridge. The avalanche occurred on a NW aspect, around 9200' (likely last night). I'd estimate the size to be 1-3' deep, and about 100' wide. 

No other avalanche activity observed today.  (ski tour up Republic Creek this morning, low visibility while I was up there).

No collapsing. Minor cracking of the fresh, dense wind drifts, though they felt quite stubborn.

New snow:  about 10", dense/ rimed forms."

From email: "Saw this recent crown while xc skiing out above Mill Creek today.  It's on the east-southeast aspect of Peak 10526 east of Emigrant Peak at ~10,200'.  In what I like to call the Arrastra Ridge Avalanche Observatory Plot*.  The photo is taken approximately 5 miles in line of sight from the crown.  It is roughly 1000' wide.  If I had to guess, the crown is 10'+ tall—definitely a very destructive avalanche. I won't venture a guess on the rating.  I'd bet good money it ran all the way to the lake at the head of Burnt Creek and rearranged some timber.

*If one wanted to create a laboratory for observing large, regularly occurring naturally triggered avalanches, this would be one of the best locations in SW MT."

A group of skiers saw a natural avalanche on an east, facing slope off of Naya Nuki Mountain in the Bridger range. It likely avalanche early in the morning on April 2.

From IG: A group of riders reported seeing three new natural avalanches on April 1. 

From IG: “North meadow creek tobacco roots today“

Experienced a very large whumpf on the Middle Basin Ridge at Beehive.

We had just finished digging pits in the first large open section of the ridge and one of our skiers was jumping on the snow above the pit when there was a large whumpf. We guessed that the whumpf could have extended out to be about 100 m total(of course this is an estimate), but the point is that it was very large. One other group experienced two separate smaller whumpfs about 200 m away on a different section of the ridge.

The large whumpf occurred at approx. 9020 ft on a west aspect. 2 smaller whumpfs occurred at approx. 9030 ft on south/southwest aspects.

We rode to the Taylor Fork Weather station, then to the Wilderness Boundary above Beaver Creek, and then through Sage and Carrot Basin. There was 13-14" of new snow throughout the area. At the Wilderness Boundary we saw several R2-D2 avalanches on a NE facing ridgeline above Beaver Creek. We dug a pit on a SW aspect at 8,800' that was 9' in depth (HS: 279 cm). We had an ECTP 11 at the interface between the new and old snow. We also had an ECTP 24 on a layer of 1.0 mm facets sandwiched between two melt freeze crusts. These results and the recent avalanche activity highlighted the instability that exists from this most recent snow. When we were leaving our pit site the visibility improved, and we saw  a R3-D3 avalanche in a high alpine bowl. This avalanche confirmed that deep slab avalanches are still a concern for our advisory area.

We dug a pit to the ground (260cm) on the west wall in Beehive Basin to target observations for the Deep Slab problem. Attached is a SnowPilot graph of the layers, hardness, and grain identification. We performed a PST but did not get any results on the deeper facet layer, possibly due to the column not being fully isolated in the 260cm pit. 

We skied/snowboarded in the Lionhead range today and dug a pit on a southeast facing slope at 8900 feet. There was about 3" of fresh on top of a 3/4" thick crust. Then about 11 inches of 1-4 finger density snow, a hard 3/4" thick crust, a 1" layer of snow, and a third 1/2" thick crust. Below this was 30 " of one finger density snow to the bottom of our pit, (and 32" of snow below that).

We got ECTN4 at 6" below the surface along an unidentified thin layer, and ECTP11 that slid on top of the second ice crust (about 14" below the surface).

Riding conditions were better than the crusty layers might suggest. We stuck to the trees, less-than-30-degree slopes, and avoided slopes leading to terrain traps. We did not observe any avalanche activity.

Our party of 6 stayed at the Hellroaring Creek hut over the weekend. The winds and snowfall were intense, with the snow turning more graupelly by mid Saturday.
We dug a pit on a southerly aspect of Mount Nemesis, near the hut around 8000.’ We noted the complex layering, including a weak layer about 20” down that failed on the 23rd shovel hit. 

On Sunday morning the sun broke through for a bit and allowed us to view the widespread avalanche cycle that occurred overnight on all aspects. Across the creek, we saw a large crown (approx 3’ in depth) in the meadows. 

An avalanche that occurred on Nemesis’s south face ran from mid mountain all the way into Hellroaring Creek, running over our old skinner. 
 

The natural slides on Nemesis’s north face were some of the biggest we have seen in any slide, knocking out a lot of trees towards the bottom.  

Large natural on the E facing head wall above ainger lake. One smaller crown above the large main crown, broke on a deep layer. Debris ran past the lake. 

Winds started cranking this afternoon in the alpine and ridge tops. Lots of snow being transported around. Ski and skin tracks were disappearing close to the ridge between laps. 

ECTP 22 & ECTP 27, down 50 and PST 75/100 end, down 50 & 80 at 7800 ft on E aspects on the ramp above Bradley Meadows

PST 45/100 end, down 180 on E aspects at 7700 ft on E/NE aspects at N end of the top of Bradley Meadows