All Avalanche Incidents for Advisory Year 2023-24

Toured into the southern Lionhead today. Yesterday’s warm weather made the snowpack more moist, and the upper snowpack was much more cohesive than in days past. Snow was glopping on skis and skins up to around 9k. I got on NE, E, and SE aspects, which were quite reactive, with more wumphs than in the last few days.

Skiers on Monday, Dec. 18 felt collapsing in the Lionhead area. They also saw an old avalanche. It likely occurred at the tail end of last week's storm. 

From obs: "Saw one small natural crown on a NE rocky outcropping around 8k, 1 foot deep and isolated. Felt a lot less collapsing than last weekend, however still found some instabilities. Notably a remote collapse that propagated around 50’ in length at around 8200’ on a NE aspect."

An avalanche along the divide between Muddy and Bear Creek. Avalanche was approximately 100 ft wide and 25 ft tall, breaking on facets just above a crust near the ground. Slide was clearly several days old, estimating it broke Friday, 12/15/23. Tracks indicate it was likely snowmobile triggered. Photo taken 12/19/23. GNFAC

Skier triggered avalanche at Lionhead on NNE, 8600 ft. Video of remote triggering slide on IG

While skiing near Scotch Bonnet Mountain skiers felt many small collapses and one very large one. 

Skiers in Republic Creek also observed cracking and collapsing while in Republic Creek. 

Multiple parties of skiers felt "thunderous whumpfs" while crossing a meadow on the way to Texas Meadows. 

Multiple parties reported signs of instability in the form of either cracking or whumpfing or poor results in stability tests while skiing in Beehive Basin on 12/17. 

From obs: "One pocket in a glade of one of our lines had a short shooting crack ahead of my skis as I set our skintrack. ~1ft. of snow propagated uphill onto my skis." E.Webb

"ECTN x 5 and ECP x 1, down 45 (shallower spot as compared to the other 5). PST 30/100 SF, 60/100 end down 58. PST 40/100 end down 55. Two large whumpfs nearby. All obs were at 8700', W aspect (meadow between gem chute and next chute to the South). " D. Sandberg 

Skiers in Bradley Meadow felt a large collapse while touring.

From obs: "Experienced a large collapse below the N half of Bradley Meadows in a small meadow - 7400 ft east aspect."

Skiers in Lionhead heard widespread whumpfing and collapsing while touring at 7,000 - 8,700ft. in Targhee Creek. 

Collapsing in Sheep Creek.

From email: "Less collapsing up there yesterday than what we've been experiencing all week, but there was one BIG collapse in one of the meadows in the valley bottom (estimated 300'+ diameter).  Remote triggers are still a serious concern."

Big Sky Ski Patrol reported two natural avalanches seen today (12/15) in closed terrain. 

From email on 12/16: "Further investigation of the avalanche yesterday showed goat tracks leading into the crown area of the avalanche. At the debris pile, it was obvious that a goat had taken the full ride in the slide that it triggered. There was a depression in the debris pile where the critter had come to rest at the surface, and obvious hoof prints trailing away from the debris pile, and then upslope for the long walk back up to rejoin the heard. There was no blood, and the tracks looked usual, with no obvious sign of broken leg(s). It is unknown if the goat was wearing an airbag or if it was deployed in the avalanche. It was a significant ride, 1K’ vt., 1⁄4 mile linear, likely of high speed, through 2nd Dictator transition, which was taken down to mostly bare ground."

From obs: "Today (12/14) I was skiing a south facing slope between 8500-9500 ft near Mt Henderson. I observed at least ten large collapses, some of which sent cracks 30 feet long. This slope had a shallow snowpack relative to the rest of the area"

Skiers in Beehive Basin heard whumpfing while touring in Beehive Basin. Others saw poor stability test results with scores of ECTPV and ECTP1. 

Two natural avalanches observed near Lionhead on 12/15 and another two observed by a separate group on 12/14. All occurred well below the high ridgelines and likely broke several days earlier. 

From obs:"We rode up Denny Creek towards Watkins Creek and spent the day below the ridge where we saw two natural avalanches. These avalanches broke 12-18" deep on weak faceted snow above a stiff crust. The first avalanche presumably happened sometime near the end of the last storm cycle (12/11), as it had a few inches of snow on the debris. The second was more recent, in the last 24-36 hours. Both were at 8500' and were on NE and E-facing slopes. "

Spent the day up near ski hill with West Yellowstone Avalanche Fundamentals course. 

Our group observed a large collapse below ski hill.

We dug various pits @ 8000' below ski hill and found HS 85-55cm on NW-NE aspects.

The snowpack structure there had weak snow at the ground capped by a stout ice crust with faceted snow over the crust beneath the recent snow.

We recorded ECTP4, ECTP11, ECT20 & a few more propagating results on facets above the crust. 

There was widespread intact surface hoar. 

A skier triggered avalanche on the SE face of Mt. Blackmore. Crown is marked.

Skinned up the closed ski area to the Fingers Meadow above the Pierres Knob chairlift. Got a substantial collapse (whumpf) while skinning and stopped to dig a pit at that location. E aspect, 8100 ft. Snowpack consisted of 6-8" of old, weak, faceted snow at the ground capped by ~18" of snow that has fallen over the last week. 

ECT broke on the old snow while isolating the column. Twice (ECTPV x 2). Clear signs of instability kept us out of avalanche terrain. 

From email: "Noted one recent large slab avalanche on a SE aspect of Miller Ridge.  Estimated to be about 100' wide and 1-4' deep.  It ran about 1/3 track or 600' vert.  No fresh snow on the debris, so it likely ran at the end of the last snowfall event."

Date is approximate. 

Lots of collapsing today near Miller Ridge (S, SE facing slopes), just 50' from the road. This continued in more sheltered areas as well. Dug on a NE facing slope at 9300', HS: 80 ECTP12 @ 40 cm. 

Got a view of the bowls behind maid of the mist and above twin falls today. Multiple natural wind slabs, up to size 2, on E and NE aspects, roughly 9500 ft. SS-N-R2D2-I.  My guess is they are roughly 48 hrs old.

Toured up toward Mt. Blackmore today with the goal of skiing the mellow SE facing meadow and familiarizing myself with the current unstable snowpack. While stopping for lunch I dug a quick pit out of curiosity and performed a CT at 8757’ on a NW aspect with HS 85cm. Results were CT11 down 17 cm within the new snow on a hardness change and a CT13 down 35 cm on old facets. Moving farther up in the basin we noticed the pictured recent D2 avalanche on the E aspect of Blackmore. As we skinned up the SE meadow, we experienced three audible whumpfs. Otherwise great skiing was found today albeit a bit thin!

We skied into Beehive Basin today and found unstable snow. The bottom half of the 1.5' snowpack is weak, sugary facets that collapsed with audible "whumpfs" as we toured up... 

Skiers on 12/21 saw 2 old avalanches while skiing in the Divide Peak Cirque. These avalanches likely happened near the end of the last storm cycle, 12/9. 

From obs: "Saw evidence of two natural avalanches on southwest aspects (see photos). The age of these slides was hard to gauge based on our lack of recent snow."

Natural avalanche on Mt. Bole. Observed taken 12/14/23. Avalanche likely released the previous weekend, around 12/9/23. 

From obs: "We were ice climbing on Mummy 3 and 4 yesterday and as we looked across the valley to Mount Bole, we could see evidence of avalanche activity on the NE aspect of the peak. It looked quite big in length but could tell a depth from that far away." 

1 team yesterday (Saturday, not me) climbed Bobo Like and Big Sleep (first 2 pitches of each). They experienced 2x collapses but no other signed of instability.

Skiers in Beehive basin observed a natural avalanche on Saturday 12/9

From email: "Solo skier that released a small pocket of snow at the bottom of Super Couloir - he was not caught and it was just the recent new snow and it didn't run far."

Riders in Taylor Fork saw natural avalanches on Saturday, 12/9

Skiers in the Southern Madison, Lionhead, and Northern Madison areas experienced widespread cracking and collapsing on Saturday 12/9.

Riders remotely triggered two avalanches while in Teepee Basin on 12/9

From email: "LOTs of collapsing again today while breaking trail on low angled S, E and W aspects.  Some collapses were quite large (100'+ diameter)."

Climbers in Hyalite saw a large natural avalanche on Elephant Mountain. 12/10 

From email "Observed a fresh slab avalanche on Mt. Henderson this morning.  E, SE aspect, 9,900'. I skied up to  investigate it and would estimate the size of the crown to be 2-4' deep and about 80' wide. Somewhat surprised by the size relative to the starting zone. Likely a natural avalanche (from about 36 hrs ago), but there were fresh sled tracks in the vicinity from yesterday, so possibly a remote trigger."

Big Sky Ski Patrol intentionally ski cut an avalanche breaking on the weak snow near the ground during avalanche mitigation work on 12/8/23.

From email: "[An avalanche] released on a ski cut, breaking on facets above a basal crust, easterly aspect, just below tree line."

Cracking and collapsing reported across the advisory area in the Bridger Range, Big Sky area, near West Yellowstone and Island Park, and near Cooke City.

Upon descending climbers saw two recent natural avalanches in the Dribbles Gully. These avalanches were failing within the new snow. 

Skiers in Lionhead saw old debris below Bald Peak on Wednesday, 12/13. This avalanche likely broke late last week, 12/7.

From IG: Pocket I set off between finger 2 and 3 at Bridger Bowl just above the road. Finger 1 had someone ski it while we were hiking and they got a face wide crack.

From GNFAC: We rode up Daisy Pass road... saw a couple 8-10" deep natural avalanches on the steep slopes above Miller Creek that probably ran in the last 24-48hours. We had multiple collapses on the NE facing slope where we ski toured to dig our second pit.

From text message: "The attached picture is a little slide that went off when I was doing small turns on an adjacent slope. That's Beaver Slide! There was more small slides south in the trees. Heard whumphing here and there." Photo: J. Onken

User comment on FB: "Lotta slides in black canyon island park."

From FB Comment: "We were seeing shooting cracks in the snow Sunday in the Black Canyon area."

Was splitboarding up near lions head ridge today. Made some bad decisions and kicked off a good slide in a NE facing chute. Was with 2 buddies, 1 of which skied the line 3 weeks ago.  Underneath about a foot of new powder snow there was a firm crust that seemed like it was old  hard windslab in the gut of the chute, and I think a sun crust on the riders left side(East aspect). We had 2 spots where we were planning to re group at, first was a small cubby area right before a slight rollover about 75 ft from the top. I dropped first, made some turns down toward the pulloff, as I pulled in, I triggered a good size slab that propagated maybe 40-50 ft across, at the rollover as I carved into the pulloff.  Pulled  all snow  out of the chute down to the ground. Seemed to have failed on sugary facets on ground/ice crust close to the ground... 

Skied around Mt. Henderson today. Was finding around 28-35 cm of new snow at 9k'. Perhaps 10cms in town. Light density.  Minor wind effect. Partly cloudy morning, turning mostly cloudy. Cold temps. Calm to light winds where I was, but lots of snow was being transported off the exposed ridgelines south of town. Quite a bit of cracking of the new snow this morning while breaking trail and while skiing, even though the wind effect was still Fist hardness.  A couple of collapses noted as well in the deeper drifts.

Went into the Lightning/Taylor Creek area of the Southern Madison’s in search of some powder skiing with the new snow. On our ascent toward Woodward Mountain via the backside, we found fresh snow varying from 2 inches at the trailhead to foot deep lightly drifted areas in the upper elevations. In the protected low angle gully we ascended this new snow sat atop either rocks or a very stout wind crust. The latter of which made for great skiing. We descended Woodward top down and assessed the possibility of thin (3”) wind slabs being reactive on the stout wind crust as the Woodward side seemed to have received a lot more loading from the storm’s E winds. As we rolled over to slightly steeper terrain, I noticed the snow stiffening just below my skis and gave it a few hops where I intentionally popped the pictured slab. With this information, we decided to carefully traverse to more protected trees and descend via a less wind loaded and hazardous route. We ski cut from tree to tree triggering a few more of these very small slabs before finding wonderful powder skiing lower on the mountain where the wind had significantly less effect. 

All of the slabs were 1 to 4 inches deep and propagated 5 to 15 feet wide. None of them possessed the mass or were on steep enough terrain to overcome and slide over the stauch wall. Overall was a great lesson in mitigating hazard and we were rewarded with some great turns. 

From FB message: "Hi! I’d like to report 2 natural slides that were witnessed in the Flanders fork of Hyalite on Friday 11/24 on the east facing aspect of the canyon. Both avalanches came from a single snow field above “Bobo Like” ice climb. These slides happened at approximately 7:45am and 8:15am"

Skiers reported triggering an avalanche on the east face of Mt. Blackmore on Sunday.

Avalanches on Henderson Mountain near Cooke City were reported via instagram on 11/9/2023. Estimating they occurred a day earlier. 

From message: "on Henderson in Cooke just above the lulu trail. It was surprising to see so much activity"

From observation: "Skier triggered windslab in the Great One off of Naya Nuki peak, skier was carried 15-20ft before arresting. Slide was triggered roughly halfway down the couloir where the right wall dips away exposing the snow to wind. Hard consolidated snow over facets, roughly 1-1.5 ft thick, ran about 50-100 ft before pouring over the cliff faces below. North- northeast aspect." 11/8/2023

A hiker at Bridger Bowl noticed a small, loose snow avalanche near the Apron. Noting that it was a, "Good reminder as to how little snow is required to have an avalanche!"

From IG: “Pine creek today, some small wind slabs and a full depth wet slide off black mountain”

From obs. (10/21): "Was out alpine climbing today and observed the north face of Blackmore had slid already."