Avalanche Activity

We skied from Henderson Mtn over to Daisy Pass and had numerous large, thunderous whumps, bother there and back.

From BBSP: "a jug of ANFO released an R2D2 avalanche that was 16" deep and 150ft wide that ran down to near the upper gate traverse level. It broke on the basal crust that had 4mm facets above."

Whumping on approach when not is snowmobile tracks. Dug a pit on a north east face slope off the Miller creek road approach to daisy pass at ≈ 9000ft . Shallow snow pack 110cm. Ectp 10 60 cm from ground 26 deg slope. Choose to ski low angle south west facing slope with no terrain above. No recent natural slides were observed. 

Started noticing cracking, collapsing, and whumfing around 7800' on east-facing slopes. ECTP 11 on our stability test. 

From obs on 01/29/2024: "Observed quite a few avalanches at the head of Republic Valley today. D1-D2. Range. Looked to be 2-3 days old on various aspects. primarily North-Northwest facing. Attached a few photos. Did not get a good shot of The headwall off Republic peak but that had also slid"

From email 1/26/24: "7 ANFO jug shots were used in D-Rt and S-1. [Areas not open to public skiing yet this season]

Joel's Belly which broke 12-18" deep 50+' wide on the wind loaded south shoulder above the joel's zip drive - majority of the debris didn't go too far, southside portion rolled off the stubborn angle and down onto the z-fan.

Z-Chute southside above traverse to lost shot bowl removed the seasons snowpack down to the basal crust. 50-100 ft wide, pulling the faceted snow off the steep rocky wall to the south and put a lot of debris on the Z-Fan and ran 100ft below the south bowl traverse.

Middle of Lost Shot bowl released but not very big."

From email 1/26/24: "The NSS avalanched R3/4, D3.5 on a 6lb. shot on a stick. There were multiple basal layers involved, including gouging to the ground. Big avalanche and not a surprise. That zone has been filling in, growing in volume, and hardening in the wind.... Unsurprisingly, it did not take much added intensity to make it avalanche."

From obs: "Similar to your complete ripout of the slope at the head of first yellow mule, this aspect pulled out naturally likely on the 25th - natural caused. No tracks around."

Starting at  45°11'13.26"N /  111°27'36.92"W, the NNE slope slid  (likely rider caused 2 days ago).
The adjacent slopes at  45°11'18.09"N / 111°27'54.78"W further west were slightly newer perhaps the 26th or late on the 25th. Each ripped down to the ground at the crown. Severe instability was present even when cresting over the slope from the entrance through the regular access to cedar - still not broke open.

From IG message 1/26/24: "2nd yellowmule. Main north facing ridge. Whole thing ripped out. Appears like yesterday, but unsure. Massive slide."

On 1/26/24 we observed two avalanches at Lionhead that appeared to have broken in the last 24 hours.

One slide broke below treeline in Denny Creek, around 100 ft wide and ran around 100 vertical feet. Looked to have broke 1-2 ft deep. Recent snowmobile tracks about 50 ft away from the flank make it seem likely it was remotely snowmobile triggered. 

The other slide was larger, it broke around 600 ft wide and ran 500 vertical ft. Didn't get a good look at the crown, but would estimate it broke around 2-3 ft deep. It broke across three gullies that sometime avalanche as separate paths. 

More avalanches were seen north of Cooke City. These avalanches likely happened on 01/25. 

Cracking and collapsing reported across the advisory area. Shooting cracks up to 100 ft long. 

The trigger of this avalanche is unknown but there are many ski tracks in and out of the path of the avalanche. Another party in the area the day before said this slope had not avalanched. 

From obs: "The location is the knoll under the Saddle Peak cliff that can be accessed by traversing through the southern boundary gate from Bridger Bowl. The slide propagated on a NE aspect going into a gully. The crown looked to be 1-2 feet tall with an approximate width of 30 feet. There are numerous tracks that go in and out of the slide path, but could not tell if it was triggered by a skier. A friend who I was with said that the slide had not been there the day before."

Skiers on 01/25/2024 observed recent avalanches below Mt. Fox north of Cooke City. 

From email: "

 I did not get a good photo but yesterday (01/24) skiing out of the yurt with friends noticed a large natural on the NorthEast facing bowl on Sheep Mountain. Similar size to the Henderson slide if not a little larger. 

~300 ft. crown and ran a similar distance (300-400ft?)"

Skiers triggered several small avalanches while skiing near the zimmer creek yurt. 

From email: "Also remote triggered a few D1 avalanches over the past 2 days. Continous cracking/collapsing even in a day old skin track. "

Also that large avalanche observed today on the SE aspect Mt. Henderson was not visible there at 4pm yesterday (1/23)

From obs: "Was out today and noticed this large avalanche on the south side of Henderson. Looks like it happened today or yesterday. Possible remote trigger, snowmobilers were riding underneath that zone. The slide looks about 200 feet across and 4 feet deep in the thickest spot. D2. "

Rode along Lionhead Ridge from Denny Creek to Watkins Creek and around into the head of Targhee Creek on 1/26/24. Saw dozens of avalanches that broke within the last week. Most of the slides looked to have broken early this week. 1/23/24 date is approximate. Slides broke on all aspects, both above treeline and well below treeline, and on both wind-loaded and nonwind-loaded slopes. All these slides looked to have broken on one of the December surface hoar layers at the top of the early season facets.

While skiing a zone called "ollies woods", a southern aspect that's relatively low angle, we noted widespread loud whumphing of the snowpack in the trees. I Spent some time traversing around the tree'd face on the way down to my group, traveling far right to a sub-ridge where the aspect changed to east, the terrain became more open, and slope angle became steeper. I felt a large whumph, paused, and turned around descending the rest of the southern aspect to the valley bottom.

Once back to the valley bottom, I saw a recent avalanche had slid just below where I was standing earlier on the sub-ridge. Looking from a far, the crown looked about 10" - 15" deep, 60'-100' wide, and fractured on a layer of facets. The slope angle was 31 degrees and at 9100ft elevation. See photo, x marks my relative location when I heard the "whumph"

A group in Cooke City observed several signs of instability including widespread collapsing, small avalanches on test slopes, and recent avalanche activity.

From obs: "Observed extremely unstable avalanche conditions while ski touring in the Woody Creek Drainage south of Cooke City for the past 4 days. While traveling through the valley floor, I noted whumphing, collapsing, and cracking in the snowpack. I was able to trigger small slides on steeper test slopes just above creek beds from 50-60 feet away. I noted several larger avalanches up high, on all aspects. We played it safe and stuck to skiing and traveling through slopes under 25 degrees and limited our exposure time under large avalanche paths."

From email: "AAI Pro 1 course to Beehive Basin. One of the students stomped on a lower angle slope directly above a large test slope. On the second stomp the slope released. West aspect at about 8000'. SS-ASc-R3-D1.5-O. Some localized cr, co while breaking trail."

From obs: "Collapsing snow could be felt underneath my sled all day up Black Canyon Loop trail, east of Island Park. There was a moment where shooting cracks spread from my ski tips to about 10 yards away on flat ground. The canyon just north my location was probably steep enough to slide."

We rode into the Throne in the northern Bridgers. On the east facing hill visible from the sleds, a slab avalanche about 1 foot deep and 100 feet wide was seen. The debris fanned out and did not seem deep enough to bury a person. A roller ball likely triggered it on Sunday (01/21/24) as there were no roller ball tracks on the bed surface, only leading to the crown. It was a bit disheartening to think that a roller ball was enough to trigger a slide.

We skinned to the runout zone of the Throne letting our runout angle approach 23 degrees. We has numerous collapses and we decided to not ascent because there is not a way to stay out of avalanche terrain, plus we were concerned about having a collapse propagate up the hill and avalanche on us.

Large natural avalanches and significant cornice formation were visible in October Bowl. We noted frequent collapsing and shooting cracks (5-100ft+) on E facing slopes at ~8000ft.

Photo taken 1/30/24

Also that large avalanche observed today on the SE aspect Mt. Henderson was not visible there at 4pm yesterday (1/23)

The slopes above the last pillow pitch slid naturally. The crown extended from high up on the cliffs to lower down and across, and the cliff face. It ran a few hundred feet (~200) . A few new inches on the skin track (3-4)

In First Yellowmule, Dave was crossing a low-angle slope and remotely triggered an avalanche in steep terrain from 750' away. This avalanche was 1-2' deep, 250' wide, and ran 200' to the meadow below. The avalanche failed on a layer of buried surface hoar. At the crown, we dug a snowpit and had ECTP10 results on this layer.

Some avalanches we saw/ triggered were on wind-loaded slopes, and others were not. All steep slopes are suspect. 

Large natural avalanches and significant cornice formation were visible in October Bowl. 

We rode into Buck Ridge today, 01/22, towards the Bear Creek wilderness boundary. Dangerous avalanche conditions exist. Skiers and riders should give themselves wide safety margins when traveling around avalanche terrain. Cautious route-finding and conservative decision-making are essential. 

We saw multiple natural avalanches in Beaver Creek, First Yellowmule, Second Yellowmule, Third Yellowmule, and McAtee Basin. The recent avalanches were large enough to bury or injure backcountry travelers (D2) and likely happened within the last 24-48 hours.

We stopped at the crown of an avalanche in Beaver Creek and found a stiff, cohesive slab of wind-drifted snow on top of faceted snow below (ECTP 13, HS=188). The avalanche failed on the interface between the wind-loaded snow and fist hard facets below. The avalanche broke 2-3 feet deep, 100 feet wide, and ran 100 vertical feet.

Some avalanches we saw were on wind-loaded slopes, and others were not. All steep slopes are suspect. 

From BBSP:

They noted 2 or 3 natural slides that occurred last night on the backside of Bridger Bowl in Truman Gulch.

From GCSAR and Bridger Bowl Ski Patrol:

A skier triggered a slide descending the skyline/nose of Saddle Peak. No one was caught. It initially triggered at the first rock band, then pulled out much wider at the second rock band. The skier was on his second lap was the third set of tracks on the peak. All tracks were accounted for and a beacon search of the debris came up empty.

Depth was described as "full depth" (2 feet) and running on the depth hoar.

Crown was 80' wide on the first horizontal band and 250' on the second. The lower crown wrappped around the ridge out of view.

From obs: "As we approached the cornice-triggered slide from yesterday below the prayer flags, we stomped around on a low-angle east-facing test slope just south of the slide to assess the presence and character of the slab. Stomping on the test slope yielded 15' plus shooting cracks from my ski tips and remotely triggered cracks about 30' further down the slope below a rollover. A subsequent test slope north of yesterday's slide produced a whumpf. A significant chunk of that cornice is cracked and ready to collapse. While jumping on the test slope almost 100 feet away from the cornice, a small piece broke off and fell onto the slope below. " 

Climbers in Hyalite saw an avalanche near Solstice that happened on 01/21. This avalanche is 1' deep at the crown and with 18" of facets snow below. 

Riders spotted a small natural avalanche on Lionhead Ridge. The slide occurred in the morning of January 21. Unknown dimensions, but weak layers in the area are buried ~18" deep, and the slide appears relatively small. 

Skiers north of Bridger Bowl experienced frequent collapsing while walking across flat terrain near Texas Meadows. Many of the collapses were small but others were "large booming collapses"

A natural avalanche broke on January 21 on Brady's Slope on Ski Hill. Walking to look at the avalanche, we triggered a large collapse and shooting cracks. We dug a pit nearby and got very unstable test results (ECTP4) on a layer of 15-20 mm surface hoar buried 18" deep. Avalanche width and vertical fall were estimated based on Google Earth measurements.

Skiers north of Cooke City near Zimmer Creek reported widespread cracking and collapsing. Both parties remotely triggered avalanches 150'+ away. 

From obs: "Remote triggerd a D1 Avalanche from about 150' away. Crown was 1-2' deep. The debris ran onto an apron that was shared with a larger slope which subsequently triggered a larger D2 Avalanche that was about 100' wide with a 3'-4' crown." 

From obs: "Remote triggered a D1 avalanche from about 150’ away from below in a meadow." 

Skiers in Telemark Meadows experienced widespread collapsing while breaking trail. 

An avalanche was triggered by skiers crossing a slope 400' below the crown. 

From obs: "My partner and I remotely triggered a persistent slide on an East facing slope at 9350ft. The slide ran off the Evil Twin ridge, just below the large main summer trail bowl of Hyalite Peak. My partner and I were spaced out ~50ft when we both felt and heard a large whumpf. We looked up and saw the avalanche slide, but were both out of harms way from the path. The starting zone was ~400ft above us and the slide ran ~500ft in total length. The crown was just over 2ft deep at its max and 150ft+ wide. The were signs of recent wind loading as we approached the bowl prior to the slide." 

2 Snowmobilers riding into the Twin Peaks area, and one decided to sidehill a slope with patchy larch trees that is 42 degrees at the top, and consistently windloaded.  The resulting avalanche took him and his sled approximately 300 feet downhill to a patch of small diameter larch trees where the trees formed a fence that strained the rider and his sled and also piled up the debris.  It was likely one of these small trees that broke the victim's leg.  They were very familiar with the area, and all the previous accidents (one fatality occurred north of this spot by 150 yds, and several full and partial burials have occurred along this ridge) that have happened in that area.  They were carrying all rescue gear and airbags(victim did not deploy his airbag).  One of the riders was at an avalanche class I put on at the toe of the slope 5 years ago.  There was no real hazard evaluation, and the riders did not observe any signs of instability prior to triggering the avalanche. Once the rider sidehilled into the open everything fractured above him in the windslab.  My partner and I had several large collapses assessing the area, and the victim's riding partner stated that they had several collapses moving the victim to the helicopter.  The helicopter landed very close to the toe of the slope.  The snow depth at the crown was 60 inches deep, with one wind slab sitting on another on facets, and at the toe of the slope the snow depth was less than 20 inches deep.  The fracture traveled roughly 800 feet in and around the larch trees near the top of the slope and it deposited debris in 3 different run outs.

Victim was buried vertically with a boot sticking out, and his riding partner exposed his face in 2 minutes.  He extricated his whole body in 8-10.  He had a broken femur and a broken hand.  As they were digging, rescuers stated that the second leg wasn't vertical, and they found it at an oblique angle to the rest of the body.  They had an inreach and sent out a help signal that was picked up, and LifeFlight was nearby.  Lifeflight was able to land at the base of the slope and take him to St. Pete's in Missoula at 1230 pm.

Photo: https://www.mtavalanche.com/images/24/twin-peaks-avalanche

We saw a natural avalanche above the first meadow of Tepee. This avalanche is old and likely happened a few days ago near the end of the last storm on 01/20. NE facing slope at ~8500 feet. 

Skiers on 01/20 collapsed a slope while approaching a cornice. This cornice fell and created a small avalanche below. 

Skiers in Beehive Basin saw a loose wet avalanche that happened on 01/20. This avalanche ran 150' down the slope. 

From obs: "Spent a day digging out the Hut in the Centennial Saturday 1/20. Our hasty pit, 20 deg. SW aspect at 7,000’ about 1/2 way into the hut showed 75 cm snow depth and various sized facets to a depth of 45 cm from the ground overlain by new snow. The structure was poor, and weak but we did not observe propagation in an ECT. Snow surfaces were damp on all aspect that we touched below 8,000’, pin wheel rollers on many steep slopes could be seen near the creek. Plenty of collapsing and “whumfing” on the way in kept us wary. Snow depths below 7,000 feet were as shallow as I have seen in 10 years operating the hut."

Skiers in the SE bowl of Flanders triggered an avalanche from the bottom of the slope. 

From Obs: "as he turned into the bowl, a remote triggered avalanche ripped out above him. He was fast to reach a safe position in the trees by the time the avalanche finished its ride. The photo shows the 3 ski tracks, and the most left one is what remote triggered above." 

Ski toured to west Woody Ridge today, south of Cooke City. 

We set a new skin track and I would estimate that 80%+ of the snow we touched created a large collapse/ whompf.  Many of the collapses were large and loud (over 100' wide).  It seemed like remotely triggering an avalanche would have been easy/ likely had we been connected to steeper slopes.

We noted widespread avalanche activity in a nearby gully (NW aspects) adjacent ski tracks from yesterday.

In our snowpit at 9700', on a westerly aspect, we had an ECTPV.  On 2mm facets, 45cms down.

I've skied that area a lot over the last 15 years, commonly during big snowstorms and elevated avalanche hazard, but today seemed like one of the most hazardous, if not THe most hazardous days for avalanches I experienced there- given the widespread nature of the PWL and thickness and sensitivity of the slab.

The warm temperatures today likely had a significant influence on the instabilities.  (35 deg F in town for much of the afternoon.)  Lots of roof-a-lanches noted today as well.

From BSSP 1/20/24: "There were large avalanches observed on Cedar Mountain, on northerly aspects. Slides appeared to
be running on basal instabilities deep in the pack."

Picture shows collapsing and cracking off skin track.

From obs:

"Widespread cracking and collapsing were observed both north and south of Cooke City."

"We stepped off the skin track and remotely triggered a small slope above the creek below. Took a closer look and it failed on surface hoar/facets 35 cm down. A skier-triggered avalanche was also seen on the west side of Woody Ridge."

Riders saw multiple natural avalanches on the ridge above Cabin Creek. They also experienced widespread cracking and triggered an avalanche on a small slope. 

From obs: "My partner and I were traveling along the ridgeline separating Beehive and Middle Basin. 60 meters before the prayer flags on the ridge, we were stomping on the cornices. We heard a very loud whumphf and the cornice directly below me fell. This and our stomping triggered shooting cracks along the ridge and remotely triggered a cornice 30 meters ahead of us. This cornice fall triggered a hard slab avalanche that was about 15 meters wide and ran at least 100 hundred meters, but we could not see the terminus in the trees. The crown was 1F wind slab failing on facets 35 cm deep. It immediately stepped down to basal facets in spots with total crown depth of 75 cm. "

"We reached the east ridge of beehive basin at 11:30 and it was warming up quickly. We considered skiing east into middle just before the prayer flags, but when approaching the slope to dig a pit we got a significant collapse and decided to ski a more conservative pitch further north. When continuing north on the ridge we saw a recent cornice collapse which triggered an avalanche, size unknown but pictured here. The conservative east slope was in the shade and skied well.

on the way out we got another sizable collapse when skiing west down from prayer flags, on the shallow, sunny western slope, when I edged out of the gully at the first dog leg to regroup with the party."

"I saw a skier triggered slide on Tyler’s hill (lookers right of prayer flags gully), as I skinned in (ss-as-d1.5-r1-u). It looked  like it propagated across about 25 ft and just pulled out on the single roll over, I didn’t get real close, and figured a picture from that distance with trees in the way might not show much."

From obs: "Snowpack was 5-8” of wetter snow on top of the old facet layer. 
Every time we stepped away from the skin track or skied untracked snow heard a few whumpfs and saw shooting cracks (most in the few foot range but a few extended 40-50’ across the slope). "

From obs: "Continued up towards Hyalite. Consistent whumphing when breaking trail.  Consistent beefy storm slab underneath 4-5” of fresh snow once out of the thick trees. Snow so unsupportive we couldn’t walk 15 feet to dig our pit. We also observed signs of recent natural avalanche activity in Divide Basin"

Skiers in Hyalite saw an avalanche near the top of Mt. Blackmore that likely happened early on 01/20 or late on 01/19.  Additionally, they saw more recent natural activity on the west side of the mountain. 

Toured up the Ramp in the Bridger Range. At the top of The Ramp/Wolverine I pushed on some small wind-loaded terrain features with skis. About three inches of soft snow moved/cracked no wider than my ski width, then one step lower a hard slab cracked out about 10' wide, 10-12" deep and did not move more than a few inches downhill due to flatter terrain supporting it below. The slab was pencil hardness which leads me to believe it was older than the last snowfall on Wed-Thurs, but possible it formed during that event if there was a period of moderate-strong wind at the ridge.

I had two other terrain-feature sized "whumphs" on similar small wind-loaded slopes directly adjacent. These hard slabs were sitting on sugary facets, and show that avalanches can be triggered on previously wind-loaded slopes. 

A natural avalanche occurred on 01/19 and was seen on 01/20 in the eastern drainages of Ramshorn Peak. 

From interaction at the gas station:

“We were riding out from Island Park. We saw dramatic, collapses, and shooting cracks. I side-hilled a small slope and triggered it 1.5 to 2 feet deep. I have never seen such unstable snow.”

The avalanche likely failed on a layer of surface hoar widespread in the Lionhead and Island Park areas. The avalanche buried part of the groomed road that crosses below this slope. 

A skier triggered an avalanche on the SE face of Mt. Blackmore near the ridge on the morning of 1/19/24.

From text:  "Hard to with the visibility but it ran almost all the way to the skin track (~800 vertical). It definitely broke 8 inches deep and 50 ft wide, but it might've gotten a little wider and deeper."

From obs: "Stepping off my skis I sank to the ground when over in middle basin. There was widespread cracking, collapsing, and whoompfing. A few smaller natural avalanches."

Multiple remotely triggered avalanches. Lots of shooting cracks and visible whomping(poofs of snow dust). 

Triggered from over 140 yards 

From obs: "Still experiencing whumphing, and cracking along the skin track. Tracks from 24 hrs ago had filled in from wind. Wind today was 3-6 mph at 8900'. HS at 8900', exposed ridge = 30" deep. We saw 2 slides a couple days old? One was either natural or possibly remotely triggered by skiers this weekend (photo attached). SE aspect, about 9000' elev. "

A snowmobiler triggered slide occurred yesterday below Sawtelle Peak. It broke on the buried surface hoar and facets about 1.5 feet under the surface. 

The avalanche:

Widely propagating remote trigger in Beaver Creek, along Buck Ridge.

From IG: “…, probably propagated a mile long, on a layer of advanced facets 30cm below a wind slab… We dug a pit yesterday and got a ct4,  ectp9, pst 25/100 on the same layer.”

From obs: "Natural & remote trigger avalanches observed on most steep terrain" in the Taylor Fork on 1/18/24. 

From facebook message: "Multiple remote triggers across this slope."

Up Targhee Creek, near Lionhead Ridge. 1/18/24

Skiers in the Highland Mountains near Butte triggered 2 avalanches on the NE ridge of Red Mountain. The first is a remotely triggered avalanche that was triggered from the ridgeline above. The second happened while a skier "ski cut the slope". This one was noted at 300' wide and 1' deep at the crown. 

From Obs: "We skinned up towards Hyalite peak today to see how the snowpack was adjusting to this new load. While we did see some point release on the canyon walls during our approach, there was no collapsing and minimal wind effect below 9000 feet. As soon as we topped out into the hyalite lake basin, a northerly wind picked up and there were supportable wind drifts scatted about. Got an ECTx on a northern aspect at 9200' before deciding to ascend a 25 degree adjacent slope. About 50' from our pit we remotely triggered two D1 slab avalanches which broke on the roll over 150' above us. Crowns looked between 1-2' and 20-30' wide. The larger of the two ran 100' more or less. Yikes, time to bail! The low angle tree skiing along the skinner was quite nice."

On the west side of Henderson Moutain, while ascending a low-angle slope toward a known avalanche path, we experienced several collapses. Halfway up the slope, Ian noted snowballs rolling down the hill and around the corner, we could see the debris that had come from the steep terrain above. We had a clear view of this slope near the snowmobiles and it had not avalanched when we began ascending. At some point from several hundred feet away, we remotely triggered the slope. The avalanche was ~150' wide, 2' deep and ran almost to the road. Across the gully, we could see large cracks but the slope did not avalanche. Above, cracking and collapsing continued and we got a view into the upper part of the gully and saw another crown of an avalanche that likely happened at the same time as the slope below. 

While riding north of Cooke City we noted many natural avalanches on east, west, and south-facing slopes at all elevations. Crowns ranged in depth from 1-2'. Most of these avalanches were not side very wide but several were including, Crown Butte, Henderson Mountain, and Miller Ridge. All of these avalanches happened near the end of yesterday's storm. 

A small avalanche was triggered from the flats 100' away by a rider as they were getting their snowmobile unstuck. 

We rode to the bottom of an avalanche on Sheep Mountain that had been triggered by riders from the bottom. This avalanche happened on Monday, 01/14, but by today it had been filled in by recent winds and new snow. From here we worked our way north of Round Lake and found 10"-12" of new snow (0.5" SWE), compared to the 5" of new snow near Sheep Mountain. Near the wilderness boundary, we found unstable snow and while getting a snowmobile unstuck in the flats remotely triggered a small avalanche from 100' away. We then rode to a northern aspect at 9600' and found 170 cm of snow and had poor results in our stability tests, with an ECTP 6 on buried weak layers below the last week and a half of storms. 
 

From here we rode to the top of Henderson Bench and dug on an east-facing slope at 9500'. While walking to our snowpit location we collapsed the slope and a small pocket of snow below a tree avalanched. Here we again had poor stability test results, ECTP 11, this area had previously been wind-loaded during last week's storm. Storm totals here were less than what we found north of Round Lake, with 5" of new snow at 3 pm (0.2" of SWE). 

Wind through the day was calm but is expected to increase tonight. Snow will continue tonight into tomorrow morning. Expect danger to rise as snow totals increase and wind begins transporting snow. 
 

Went for a short tour near bacon rind, next pulloff to the south, toured up the burned out hill right across the street. It was real windy leaving my vehicle. Some notable whoomphing, and cracks forming 30 ft around me. I probably won’t be riding down there for a bit, the low angle stuff I like is too thin. Real thin down there with only about 40-60cm on the ground. Got a CT1 SC  Q2 breaking about middle of snowpack, ectn 2, and ectp24. 

From FB: Taylor’s Fork today, 8-10 inches of new snow last night. A few small slides but tons of cracking.

We receive vague reports of a group reporting multiple remotely triggered avalanches north of Cooke City on 1/16. A member of this same group similarly triggered an avalanche on Sheep Mountain on 1/14 (video overview attached to the entry), so the reports of avalanches yesterday are likely reliable. 

Rode up Denny Creek and out along Lionhead Ridge through Watkins Creek to the divide with Targhee Creek. Saw evidence of numerous older avalanches along the ridgeline and in lower steep meadows that likely broke last week (1/10-1/11). The crowns of these slides were blown in, but would estimate they generally broke 1-2 ft deep. Some broke quite wide ~1000 ft. Saw a couple smaller slides that looked to be a bit fresher as well. 

Got a number of collapses and shooting cracks as we rode today, shooting out 20+ ft. 

Stopped and dug a pit at the crown of an avalanche that broke on the north end of ski hill (likely during last weeks warning). Broke ~1 ft deep, 50 ft wide and ran 100 vertical. Another similar slide broke at the same time on the south end of ski hill. Today, we got an ECTP12 on the surface hoar about a foot deep.

The snowpack remains unstable and human triggered avalanches (including remote triggers from a distance) remain likely. Expect the danger to rise as it snows over the next couple days. 

From obs: "Wind slabs at the top of the ridge approximately 4-8 inches deep. Continued wind loading down the wolverine bowl, slabs softer the lower you go. Snowpack has about 1.5 feet of facets with a hard layer on top. New snow building up on top of that layer. Saw one small natural avalanche nearby, appeared a day old."

Riders saw a small wind slab avalanche in the Beaver Creek area of Buck Ridge

From FB Messenger: "Major fractures and shooting cracks across whole hillsides today. Dry Fork. Targhee Pass."

From Obs: "While riding today on Lionhead we saw several natural releases on steeper terrain Mainly on Targhee Peak. On all aspects of slopes we experienced large cracks and collapses that would extended 75 plus yards ahead of our sled. We did not venture into steeper slopes but it sure felt like they would slide easily if we did!"

Second Ob from FB Messenger: Shooting cracks on many slopes. Watch the video at 10:30 for examples 

Riders near Lionhead triggered a small avalanche while descending a steep rollover. The rider was 20' away from where the avalanche happened. 

A snowmobiler triggered an avalanche from the bottom of the slope as he rode past a gulley below Sheep Mountain. The avalanche barely missed him. The avalanche was approximately 100' wide and 2' deep. It failed on a wind-loaded slope, ESE-facing, and was large enough to bury or injure a skier or rider.

Riders in Black Bear Cayon saw a small avalanche on a wind loaded slope that recently happened, either on 01/14 or the day before on 01/13. 

From email 1/13: "I observed a large whumpf in a flat meadow, around 8500'"

From email 1/13: "We observed widespread shooting cracks on all ridges and all NE facing slopes. Cracks would propagate up to 200’ in front. Heavily wind effected sastrugi conditions."

On 1/12/24, a skier triggered a 2 ft deep avalanche on a wind loaded south facing slope at 9700 ft near Big Sky and was caught and carried by it.

From obs: 

"Widespread collapsing and cracking.  The collapsing was not especially audible, but the cracks often shot out 50-100' spectacularly- while setting an uptrack, and on descents.  The collapsing and cracking was much more pronounced above 9600', and was happening on the new/ old snow interface.  This was somewhat surprising in this location, because the old snow surface was Very heavily tracked by snowmobiles prior to this storm cycle." B. Fredlund

"Collapsing, shooting cracks (30ft+), and whumpfing noted while breaking trail on the W aspect of Henderson. Frequency increased with elevation. " Anonymous 

From Obs: "Broke loose a slide just below the radio tower standing above the crown. Broke about 30 cm down on a layer of weak snow."

From email 1/12: "From this morning. Looks to be 1_1.5' deep. Maybe  a few different ones based on what I can tell." 

Email later on 1/12: "Thinking about it more, that avalanche might have happened last night.  (with .4" of SWE at Fisher Creek since 4pm yesterday, and increased wind speeds). Almost a full reset of the surface snow up on west Mt. Henderson this afternoon."

From Obs: "While riding around we frequently saw large shooting cracks on any slope with a slight wind-load/wind-effect. Near the wilderness boundary we saw these large cracks across the snow surface. In quick hand pits we easily found a weak layer of surface hoar below the recent snow that was 3-4cm long crystals, standing upright!!!"

From Obs: "At Sunlight Basin, we remotely triggered an avalanche while walking on the flat ridge above a wind-loaded slope. The avalanche broke below a 12" deep slab with 1.5" of snow water equivalent in the slab, and it failed on a layer of large (1-1.5cm) surface hoar."

From obs: "We had multiple collapses during our ski, and one 40’x40’ slope had a large collapse on the trip up and again on the way down. I noticed one meadow that had collapsed before we were out, and the new snow had sheared off of several downed logs."

From email on 01/13: "Toured into Republic creek with our class. Noted two D2 soft slab avalanches. One on a west aspect and the other on an east aspect at about 9000'. I estimate the crown was 15-40cm deep and likely ran on the same layer as other recent avalanches in the area." 

From email on 01/13: "From Miller Ridge today, I had a brief look into Sheep Creek, and to the mountains south of Cooke City, and observed 7 fresh slab avalanches (that happened in the last 1-3 days).  Will send photos of them later if I can get better views.

Most of them were on NEerly aspects, and appeared to be on the new/old Jan. 5th interface.  Mid and upper elevations, most commonly in wind loaded terrain.  Some propagating a few hundred feet wide. "

From email on 01/14: "One crown on the Middle Siren, probably part of the last cycle."

From Obs: "Saw a natural avalanche on the east side of Henderson from the Lulu Pass Rd. Also observed a natural on the east side of Sheep Mountain. These likely happened during or near the end of the last storm on 01//10. "

From Obs: "We also saw a small wind-loaded slope that was triggered (remotely) by riders yesterday, and we triggered a similar slope today. These were short slopes, but the slabs broke over 1 foot deep and as wide as the terrain feature, and they were triggered from adjacent flat terrain 10-40 feet away (remotely triggered). "

Our lower ridge has not been controlled or touched yet this year so very indicative the backcountry snowpack. It released sometime before the morning of Jan 10.

See picture.

Skiers north of Cooke City saw widespread shooting cracks and frequent collapsing while on Henderson Moutain. 

A climber in Hyalite reported cracking while in a wind-loaded gully. 

Near the bottom of their ski run a skier and a group triggered an avalanche that broke above them. This avalanche did not run far and stopped above the skier. No skiers were caught or carried. 

We toured up Tyler's Slope and dug at 9,200' on an west-facing slope. There was a 6" slab of snow sitting on fist hardness facets that propagated in our tests (ECTPV x2). Approaching the pit site we has some collapsing and shooting cracks. Continuing upslope we saw the cornices on the ridge had all broken and pulled out the wind-loaded pockets with one slope sliding 100' distance. These likely occurred last night.

We then dug on a east-facing slope to the north of the cornices and found 105 cm of snow and a 1 foot deep slab that broke in our test as an ECTP3. Low test scores, recent avalanche activity and cracking and collapsing was evidence of the snowpack's instability.

Skiers north of Cooke City experienced widespread cracking and collapsing following recent snow and wind. 

While approaching Lionhead Ridge skiers intentionally triggered an avalanche on the steep E, NE facing terrain below the ridge. This likely happened on a buried layer of surface hoar. Lower down widespread cracking was observed that extended well in font of the skiers and on a less steep slope cracking in all directions 50' wide. Along the ridgetop cracking continued and sections of cornice fell and avalanched below. 

A skier at Mt. Blackmore saw multiple natural avalanches and one skier triggered avalanche. These likely happened earlier in the day or the day prior, 01/07. 

Skiers on Woody Ridge south of Cooke City saw a natural avalanche on 01/08 that likely happened on 01/07. This avalanche was 8-16" deep and ran a few hundred feet down the gully on a wind-loaded slope. 

From email: near Cooke city, "One could initiate dry loose facet sluffs on steep shady slopes, with ski cuts.  And there were a few more natural dry loose facet sluffs noted on east Henderson off the ridgeline from last 24-48 hrs."

While approaching a test slopes riders remotely triggered two 6-12" deep wind slabs. The first was on a NE-facing slope and the second at a E-facing slope both above Muddy Creek at 9400'. The first of these broke on a layer of buried surface hoar below recent snow. 

Loose snow avalanches were triggered easily from the ridgeline. These avalanches would start from new and wind-drifted snow but entrain larger amounts of snow from facet weak snow below. This resulted in gouging sluffs that were deeper than just new snow. 

Riders at Buck Ridge saw a natural avalanche that likely happened on the morning of 01/06 following a storm the day before. From obs: 

A skier in Hyalite saw lots of wind-drifted snow on Mt. Blackmore and observed a natural avalanche near the summit. Additionally, they saw several smaller loose snow avalanches during their tour. 

Skiers in Maid of the Mist noted multiple nature wind slab avalanches with crowns ranging from 6-12" in size. 

Skiers on Hyalite Peak noted a small wind slab avalanche on an easterly aspect.

Skiers in Beehive Basin on 01/06 intentionally triggered two small loose-snow avalanches through ski cutting and one unintentionally when skiing downhill. These avalanches started in the new snow as point releases but entrained the weak-faceted snow below.  

Skiers saw recent avalanche activity north of Cooke City. These avalanches happened following a storm on 01/04 into 01/05 and likely broke early on the morning of 01/05. 

Skiers triggered a couple long running loose snow avalanches that entrained much of the weak snowpack. On Hnederson Bench near Cooke City.

Still getting collapsing/ whumphing of the snowpack in isolated areas around Cooke City.  

We experienced about 4 good collapses on Monday north of town (with approximate diameters about 25-30').

And noted where a natural cornice fall had triggered a small slab avalanche about 30' wide. 

A skier intentionally pushed off a small, loose snow avalanche in Bear Basin. The slide consisted entirely of unconsolidated facets. 

Skiers in Hyalite experienced a large collapse and cracking while approaching. From obs: While descending "the slope in front of me collapsed, with shooting cracks about 25ft in length. Both my partner and I experienced collapses the entire way down the slope while skiing."

From obs: Lots of wumphing that often propagated 20-30’ around us. Observed above 8000’. Our travel was mostly on S to E aspects."

Skiers felt collapsing while touring near Heather Lake.

From obs: "I got one relatively large collapse as I stepped out in the open near Heather Lake, and then 5-6 smaller ones as I looped around above it."

A sledder on an east-facing slope got a slope to crack and move a couple inches, but not avalanche.

Skiers in Jardine saw natural avalanches on northern slopes. These likely occurred following storms on 12/26. 

I toured up the private property line to the ridge between Beehive and Bear Basin, I skied partway down into Bear Basin from where the prayer flags used to be. I was breaking trail back up and Clyde (dog) was wallowing in the facets so I gave a big jump to try to pack in the skin track better for him and got a nice whumph, cracks shooting out about 10'. Some slopes had fresher snow forming a slab over facets, some slopes had more facets than slab, the west side going back into Beehive had a stout melt freeze crust underneath a few inches of snow. I didn't go looking for buried surface hoar so I can neither confirm or deny its existence.

On 12/28 we saw a recent avalanche low on the east face of the Thone. It appeared to have broken naturally during the strong downhill wind event in the Bridger Range on Monday (12/25). A 6-8" deep wind slab broke over facets approximately 100 ft wide and ran 100 vertical feet. 

Skiers experienced cracking and collapsing on Lionhead Ridge on Monday, Dec. 25th while breaking trail on the NE side of the ridge. 

Skiers in Hyalite experienced many large collapses after the recent storm, 

From obs: "Despite the unconsolidated snowpack, I had 25+ significant collapses while breaking trail, with shooting cracks up to 50ft long. The collapses created visible waves on the surface of the snow and shook small trees and weeds sticking through."

At the ridgeline above the Ramp,  freshly formed wind slabs were easily triggered on a test slope. Cracking in these freshly formed drifts was also seen in any wind-loaded location.

From email 12/23: "Continued, widespread collapsing today.  About 10 good ones, and that was with very minimal trailbreaking/ about 700' vert."

From YouTube comment 12/22/23: "I am an alpine climber - descended from Barronnette today, went south all the way down the ridgeline and descended the gully above the start of the XC trail. Heard 10+ instances of whomping and slope collapsing under my feet on both avalanche and non-avalanche slopes on N & E aspects."

From email 12/23: "Widespread collapsing yesterday.  Approx 20 significant collapses.  Many shaking trees 50'+ away."

A skier traveling north of Cooke City saw a recent natural avalanche, this likely happened earlier in the week and was noted as "relatively fresh". 

From obs: "When moving through fresh snow or stepping off the skin track, we felt many localized collapses. Near the top of the ridge, we felt a large collapse."

Toured up bacon rind today (12/20) with the idea of skiing off Ernest Miller ridge. Temps were above freezing when we left the trailhead and up to 9000’. On our approach we had several collapses with cracks up to 15’ out. We found a HS of 50cm and had mixed results in our pit. We stayed in the glades below the ridge, the skiing and riding was quite good. Exiting the basin was a bit sporty with minimal snow coverage. 

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.