Regional Conditions for Southern Madison

Small snowmobiler triggered avalanche in McAtee Basin. From Instagram: "I watched a snowmobiler set this avalanche off today" T. Chamberlain

Small snowmobiler triggered avalanche in McAtee Basin. From Instagram: "I watched a snowmobiler set this avalanche off today" T. Chamberlain

From email:

"I wanted to make you aware of a snowmobile triggered slide in Lionhead today. Fortunately, I was not injured, was able to stay completely on top, climbed through the majority of the snow wash after seeing it begin to break, and relatively slowly slid down with the last of the moving snow while still on the machine. When I came to a stop, I stood up and was completely free of the snow. Our group is trained in avalanche safety, practiced beacon use prior to leaving town in the morning, were wearing avy gear, and were very fortunate that this ended up the way it did. 

A clear reminder that this can happen to any of us and to be careful out there."

Photo: Anonymous 

Snowmobiler triggered avalanche near Reas Peak on Sunday, 1/19/20. He was able to ride through it uphill. Photo: R. Gravatt

Snowmobiler triggered avalanche near Reas Peak on Sunday, 1/19/20. He was able to ride through it uphill. Photo: R. Gravatt

From obs: "I was on the west side of Pioneer Mtn digging a pit for YC Ski Patrol. I heard a few groups of snowmobiles cruising around the foothills of cedar. I turned and saw two snowmobilers cresting the ridge above the slide pictured as the debris was settling down. The sledders enjoyed the view for a few minutes before turning back the way they came and stumbled upon the slide they had unknowingly triggered. They skirted around the side of the crown and stopped for a few minutes. Based on the height of the rider off his sled, I would estimate the crown to be roughly 10’ at its max height. NE aspect below Cedar" Photo: J. Marcinko

With only 3" of new snow overnight, a cornice triggered a large avalanche at Lionhead early this morning. It broke 3 to 4 feet deep and propagated on a buried weak layer. This is the only stability test we need today, human triggered avalanches possible and the management strategy is to avoid steep slopes or be clear about your risk tolerance if you are poking into avalanche terrain. Photo: GNFAC

From e-mail: "2nd hand observation arrived at site about 5 minutes after slide. Triggered by sidehilling snowmobiler but was not caught up in it... looked approximately 50 ft wide 150 ft vertical. Did not appeared to be very deep" Photo: P. Gish

The crown of this snowmobiler triggered avalanche tapered to a thin slab. These thin areas of the slope are prime zones to trigger a slide from. Photo: GNFAC

A small but relatively deep avalanche triggered by a snowmobiler on Tuesday, 1/14/2020. 30 ft wide. Ran 20 vertical feet. This avalanche broke to 2-3 ft deep, to the ground. This is the second time this year this slope has slide, it also avalanched in mid-December. Photo: GNFAC

Yellowstone Club Ski Patrol triggered a slide with explosives breaking at the ground during avalanche mitigation work on Friday, 1/10/2020.

From Yellowstone Club Patrol: "It’s a NE facing slope at 8500’ ... got an avalanche to release on an old layer of well defined surface hoar (perhaps from mid-December). In some areas it stepped to ground. The crown was 2-4’ deep and the avalanche was recorded as R3/D2. The avalanche slid to the bottom of the runout and placed 3-12’ of snow in the road and completely blocked the road. This was a relatively large slide for this particular path this early in the season."

Photo: YC Patrol

February 1, King and Queen of the Ridge at Bridger Bowl (fundraiser). This is the Friends of the Avalanche Center’s second biggest fundraiser of the year. Come on out and help us raise money by hiking and skiing laps on the ridge. Prizes, camaraderie and a good time is guaranteed. Register with Bridger to hike in the event, and create a pledge page to raise funds with your Ridge laps.

We found 115cm of snow and a poor snow structure. Unfortunately it was foggy and we had zero visibility. Our snow pit site was marginal, but it's always worth taking a look. Weak, faceted snow was on the ground, very similar to most slopes in the Madison Range. Photo: GNFAC

We visited the avalanche that was triggered by a snowmobiler and partially buried 2 people on January 4th. The crown was 10 feet at the deepest part. Photo: GNFAC

We visited the avalanche that was triggered by a snowmobiler and partially buried 2 people on January 4th. The crown was 10 feet at the deepest part. Photo: GNFAC

Snowmobilers triggered this slide in the 3rd Yellow Mule off Buck Ridge on Saturday (1/4/20).

 @carter.olson

A natural avalanche crown was seen on Yellow Mountain near Big Sky on Saturday morning (1/4/20). Photo: A. Schauer

A party of three skiers remote triggered avalanche with at least 6' crown off N face of Mt Porphry along rockband near summit on 12/29/19. They triggered it after tyhey had found "Three pits dug on NE face ascending Mt Porphry indicating increasing stability and no clean propagation. Approx 150-210 cm deep snowpack." Photo: G. Alsentzer

Avalanche in 2nd Yellowmule. Likely broke during storm on 12/24. Less than a foot deep but ~150 ft wide. Photo: GNFAC

We toured up to about 7700 feet on a NE facing aspect in the N Madison, upon entering the bottom of the meadow we had several large collapses and then one very large collapse that propagated 100+ feet uphill while on lower angle terrain below the steeper terrain Of the meadow above. We dug a pit, we got an ECTP 10. The pit was 75 cm deep, we found basal facets with an ice crust on top and About 40cm of denser 3-4 finger snow above the ice crust. Photo: A. Palombo

Riders saw these recent slides on 12/15 near Carrot Basin. Photo: A. Wheeler

Riders saw these recent slides on 12/15 near Carrot Basin. Photo: A. Wheeler

Riders saw these recent slides on 12/15 near Carrot Basin. Photo: A. Wheeler

On Friday (12/13) there were natural avalanche crowns in Carrot Basin of Taylor Fork. These were a few days old, but show the potential to trigger slides on a buried persistent weak layer. Photo: GNFAC

On Friday (12/13) there were natural avalanche crowns in Carrot Basin of Taylor Fork. These were a few days old, but show the potential to trigger slides on a buried persistent weak layer. Photo: GNFAC

On Friday (12/13) we rode into Taylor Fork and found a weak foundation of the snowpack, Recent snow has created unstable conditions. Our stability tests showed unstable results on two weak layers. Photo: GNFAC

Skiers at Targhee Pass near West Yellowstone reported: "We got a few good collapses while skinning up through east-facing low angle meadows, and got some serious cracking and collapsing while stomping on fresh wind pillows just below ridgeline on a northeast-facing slope at about 8200'. We dug down at one of the cracks and found a 35cm thick F+ slab that had failed on a layer of 4-6mm depth hoar. Cracks propagated close to 100'..." Photo: A. Schauer

Riders reported multiple natural slab avalanches on N facing slopes. Photo: R. Rustigian

Riders reported multiple natural slab avalanches on N facing slopes. Note widespread crowns along slope in background. Photo: R. Rustigian

This natural avalanche on the northeast side of Crown Butte near Daisy Pass (Cooke City) almost caught people below. Approximately 2 feet of snow has fallen with wind and the avalanche danger is rated CONSIDERABLE. Photo: B. Whittle

Photo taken 12/6 near Two Top, south of West Yellowstone.

From email: "South facing stuff was thinner than I expected and north and west facing was a lot better than I expected. South facing stuff was 59cm deep and we had multiple ECT-P 14’s between the facets at the bottom and the newer snow."

Photo: B. Radecky

We sledded into Buck Ridge (12/4/2019) for the first time this season. The riding was supportable and soft, but we sank to the ground when we stepped off our sleds. This poor snowpack structure makes avalanches possible to trigger, and will create bad avalanche conditions when more snow loads on top. Enjoy the powder in low angle terrain. Photo: GNFAC

This is a close-up of the angular Depth Hoar grains found near the ground in the mountains south of Big Sky to West Yellowstone. These are weak and cannot support a lot of snow weight. Avalanches will break near the ground on these. Photo: GNFAC

At the bottom of the snowpack is a thick layer of weak and sugary, faceted snow called Depth Hoar. These large grains do not bond well and form an unstable foundation of the snowpack. Avalanches will break at this layer. Photo: GNFAC

We put up the Taylor Fork weather station today (12/03) and it is churning out hourly data. Check it out here: https://www.mtavalanche.com/weather/stations/taylor-fork

We partnered with the Gallatin Valley Snowmobile Association to put in two new beacon checkers at the Taylor Fork and Buck Ridge trailheads. They are working great!

Thanks GVSA! Photo: GNFAC