Avalanche Activity

As we returned to Frazier Basin from below, we saw five natural avalanches on the southeast-facing wall of the basin. These had occurred while we were skiing the terrain below. They entrained only the 1 to 2 inches of snow that had fallen during the day. However, they were notable in that they ran 500 to 700 vertical feet. They were likely initiated by warming from the proximal cliff faces. They indicate that the new snow may not bond well to the old snow surface. A crust formed by the recent warm temperatures and sunny skies is the subsurface that snow is falling on. This will become a more significant concern as more snow falls this week.
 

From obs 3/20/23: "Yesterday we toured up into Emigrant gulch. At around 2pm we observed a small point release on the East face of Emigrant, either a small cornice break or wet loose, that ran for about 200ft before stepping down to a deep slab that appeared to be about 3ft deep and 100ft across."

Myself and two partners were skiing in the crazies 3/17-3/18. Dug 2 pits and got similar results, ectn15 18cm down and n28 30cm down with depths of 300-400cm and no deeper pwls on N/NE aspects at 8300ft and 9600ft. No recent avalanche activity other than a few small 6in storm/wind slabs on southern aspects. Snowpack was very right side up everywhere we toured and had skied 3 different NW to E faces. On 3/18 we headed to ski a NE facing couloir at 10000ft, skinned/booted the first ~300ft and found similar snow to everywhere else. About halfway up hit a rocky section with some depth hoar, I noted plate crystals up to 1cm wide at ground. Should’ve turned around there but thought maybe it was just a short rocky section. I had also just measured the slope angle at 52 degrees which gave me false confidence there would be no developed slab. Wallowed through weaker snow for another ~50ft then finally decided to turn around due to the difficult boot packing, hitting our 3pm turn around time, and the weak snow pack. As I booted to the middle of the line to find better snow the slab broke off 10-20ft above me wall to wall. I was the only one caught and was carried 500ft of vertical. Didn’t get buried and no lost gear so extremely lucky all around. The avalanche was estimated D2/R4 with a 18-30in crown and 30ft wide.

From obs 3/18/23: "Watched two riders on the north side of Henderson / Daisy pass high marking. One triggered an large avalanche and got stuck at the crown. Crown was taller than him. Guessing 8-10’ deep and 200+ yards wide. His friend had his back turned to the slide and didn’t see it happen. We were across around the sheep mtn/ Scotch Bonnet area and watched the whole thing happen. We boogied over there as fast as possible to help."

More media and story: https://www.instagram.com/p/Cp8qvlfO4sM/ (Credit: C. Diffley)

Attached are a few photos of old deep slab avalanches north of town. 

The second is the south face of scotch bonnet. Hard to tell the depth of the crown but it’s very visible from the lulu road, so probably pretty deep.

Slab avalanche on NE facing slope at 7,500 feet - slid to the ground.   

Big scary avalanche on a wind loaded slope on mount Bole.

Toured into the hellroaring creek 3/15-3/19. Snowing and blowing hard on 3/15 till approx 1500 hrs when wind veered to the north and skies cleared for the rest of the trip with generally cold temps and light winds. Solar aspects heating up in the day with extensive sun crusting on steeper slopes facing the south half of the compass. Observed aftermath of extensive avy cycle which prior party reported occurred approx 3/10-11 at higher elevations on Nemesis (above 8000 ft.). This is consistent with what we saw as new snow from 3/14-15 covered the debris piles at the bottom of large paths on SW face, however lower elevation steep slopes above creek at approx 7500 ft may have ran during the storm on 3/14 as less snow covered that debris. Everything observed were deep slab avalanches breaking approx 90-120 cm down. We did not investigate the weak layer. Suspect it to be the crust facet combo observed by a previous party in early March. Heavy wet snow possibly mixed with rain on 3/14-15 likely tipped the scales for these lower elevation slopes below 7500. No signs of instability of the new storm/wind slab during the five day trip, however we did get a few large collapses but these were isolated to heavily wind loaded areas in more exposed terrain. No other natural or human triggered avalanches observed during the trip. Many machiners were out testing steep slopes after the storm and we saw no signs of any human triggered avalanches. Seems higher elevation slopes that were not heavily wind loaded faired well overall. We did not measure height of snow but judging by the buried hut and barely the non-motorized boundary signs partically buried, thinking about 10 feet deep at 8000 ft. 

Attached are a few photos of old deep slab avalanches north of town. 

The first photo is a south face north of round lake above 10,000’. The crown was mostly filled in but the deepest exposed part was 2-3’ deep. 

Riding around Lionhead and into the back bowls revealed an extensive avalanche cycle that occurred with the Avalanche Warning 2 days ago. Some slides were hard to see since they were buried in snow while others were more fresh. Crown lines near the ridges, debris piles at the bottom of slopes, and debris pushed high onto trees were evidence of the recent activity. Many slopes avalanched; more than we've ever seen in this area.

We dug in 1 crown and measured 11" of SWE above the weak layer (1mm facets) that avalanched. Every weak layer has a breaking point, and this layer needed about 11 feet of snowfall to get it to avalanche.

From obs: "Saw this natural D2 soft slab off the east aspect of Miller Ridge. The crown looks shallow, so I’m guessing it ran at the storm interface."

From another obs: "A few recent slides were visible today on south, east and west aspect around goose lake zone."

From the FAA road up Sawtelle Peak outside Island Park we were able to see many crown lines and debris piles from the last 2 days of Avalanche Warnings. Most avalanches involved new snow, but there was 1 deep avalanche on Mt. Jefferson's east face that was large (D3). The FAA did avalanche control and an avalauncher round triggered a small, but deep slide (2-5' deep) and a larger explosive on another slope yielded no results. We saw 8 backcountry avalanches from the road. These were east and north facing, the only aspects available for viewing.

The snowfall totaled 3' and it will take a few days for the snowpack to become more stable. In the meantime, be patient and stay off of steep slopes.

We saw a natural avalanche that likely failed this morning near the Gallatin River across from Bacon Rind. 

We saw two natural avalanches with a brief period of better visibility. Both appeared to release within the new snow or at the interface. 1-3 feet deep. The large appeared to run about 500' vertical. 

Toured into the hellroaring creek 3/15-3/19. Snowing and blowing hard on 3/15 till approx 1500 hrs when wind veered to the north and skies cleared for the rest of the trip with generally cold temps and light winds. Solar aspects heating up in the day with extensive sun crusting on steeper slopes facing the south half of the compass. Observed aftermath of extensive avy cycle which prior party reported occurred approx 3/10-11 at higher elevations on Nemesis (above 8000 ft.). This is consistent with what we saw as new snow from 3/14-15 covered the debris piles at the bottom of large paths on SW face, however lower elevation steep slopes above creek at approx 7500 ft may have ran during the storm on 3/14 as less snow covered that debris. Everything observed were deep slab avalanches breaking approx 90-120 cm down. We did not investigate the weak layer. Suspect it to be the crust facet combo observed by a previous party in early March. Heavy wet snow possibly mixed with rain on 3/14-15 likely tipped the scales for these lower elevation slopes below 7500. No signs of instability of the new storm/wind slab during the five day trip, however we did get a few large collapses but these were isolated to heavily wind loaded areas in more exposed terrain. No other natural or human triggered avalanches observed during the trip. Many machiners were out testing steep slopes after the storm and we saw no signs of any human triggered avalanches. Seems higher elevation slopes that were not heavily wind loaded faired well overall. We did not measure height of snow but judging by the buried hut and barely the non-motorized boundary signs partically buried, thinking about 10 feet deep at 8000 ft. 

We investigated an avalanche that broke naturally approximately one week ago on a north facing slope at the head of Sage Creek. 

On our ride up the Taylor Fork, we saw several natural avalanches that appeared to have broken about a week ago. This avalanche was in Sage Basin.

On our ride up the Taylor Fork, we saw several natural avalanches that appeared to have broken about a week ago. This avalanche was in Sunlight Basin. 

From Obs: "Heard tree breakage, saw plumes of snow and sliding snow at the bottom of the slide path. Our group spoke with the sledders and skiers that were on the slope and confirmed none were caught. Skiers reported feeling slide tremble and backed down the mountain. The main breakage was near top of the third shoot from the lookers right."

From Obs: "Big (tennis court size) collapse and whumpf on the upper meadows at Telemark Meadows in flat terrain. No other reactivity to report from a few laps on the main ski slope."

From obs: "I triggered an avalanche on the way back down the mountain. I'm unsure of the exact location but a buddy said it was under bear tooth butte. I was able to outrun the avalanche, and there were no injuries."

Snowmobile triggered on a path called "Marty's" above Daisy Pass road. This was similar aspect as the slide on Crown Butte yesterday, and likely had a similar snowpack structure. We checked the debris for a beacon signal to be sure no one was caught, and did not find one. This may have been triggered today (3/12). Photo: GNFAC

From Obs: "I also saw another (much) smaller 1-2’ deep slide on the west-facing road cut just north of the Bacon Rind pullout."

From Obs: "I went on a little loop up and around Red Mountain today and have a couple of slides to report. Most notable was one that spanned about 2000’ of the north side of Red Mountain. It seemed to be 1-3’ deep in the newer snow, for the most part, but a portion of it broke 15’+ deep and ran at the ground. Judging by how little snow was on the debris, I’d guess it ran sometime Friday night or Saturday. This bowl frequently produces large avalanches, but this one was a real peach."

Via IG: “Large natural avalanche on the east side of redstreak peak down near West Yellowstone. 

And then another natural one right on the shoulder of white peak on the boundary.”

Via IG: “Electric peak via Betty gulch avalanches. Assuming they are natural!”

From Obs: "On Saturday we toured up Dudley Creek. At around 1pm we ski cut an isolated, wind loaded pocket on a SE aspect at approximately 9200ft elevation and released a wind slab (see photo). The slab was about 20 feet wide, about 1 foot at it's deepest, and ran for about 200 feet. Staying wary of wind loading, we dug a pit on a NE aspect, in a spot without evidence of significant wind loading, and received an ECTNX. Although we did not identify any failure on buried weak layers in this location, it will remain something to watch for with more snow and warmer temps on the way."

From obs: "Large avalanche with small tree and branch debris. Located on the lower NE bench face of Mt Abundance, near Lake Abundance. There were snowmobile tracks near the slide but could not determine if that was the cause. Approx 2000 feet across. Possibly 4-6 feet deep but couldn't tell from the bottom of the hill." 

From FB message: "triggered this today (3/11/23) in Cooke City south side of Crown Butte."

From obs 3/11/23: "Saw a deep crown today in Republic Valley. This is peak 10383 (just north east of republic peak). Crown looks about 100 feet wide and probably 5 feet deep. Couldn’t see debris or how far it ran."

While driving into Cooke City this afternoon (3/11/23) I saw recent large (D2) natural avalanches on north and northwest aspects above Silver Gate, and there was a large avalanche in the main gully on Town Hill (southerly aspect) above Cooke (photos attached).

From obs "We rode up Lulu Pass at 8AM on 3/11/23 and saw the debris from a large D2.5-3 avalanche on the SE face of Fisher Mtn. Similar slide path to the large avalanche on Fisher earlier this season."

From GNFAC 3/12: "Today we rode north of Cooke City and looked at recent natural and Human-triggered avalanches. The slide on Fisher Mtn. was very large and appeared up to 10 feet deep. It had much more volume in the debris than the slide that was triggered on this same path in December."

Riders observed many natural avalanches at Lionhead. They likely failed between Thursday night and Saturday (3/9-3/11).

Today we rode north of Cooke City and looked at recent natural and Human-triggered avalanches...

We saw two slides that had not been reported previously. One natural on the east side of Sheep Mtn. that was a hard slab of wind-drifted snow on a heavily wind loaded slope near the high ridgeline at 10,500'.

While driving into Cooke City this afternoon (3/11/23) I saw recent large (D2) natural avalanches on north and northwest aspects above Silver Gate, and there was a large avalanche in the main gully on Town Hill (southerly aspect) above Cooke (photos attached).

From IG message 3/11/23: "...yesterday, at Fairy Lake, very windy and this slid naturally sometime between when we got to the area at noon and 3oclock. There was also a smaller natural wind slab in the northern bowl with arrowhead. Observed wind loading all day."

From obs 3/11/23:

Several avalanches observed D2-D2.5.
Crown depth 80-120cm
ENE @ 10,000’

E @ 9700’

SSW @ 8800’

PHotos attached of some natural avalanches near Cooke City today (3/11/23).

Avy1: NW aspect, around 10,000'. (This starting zone also avalanched in a similar way around Feb. 21).

Avy2: E aspect, around 9,000'.

From IG message: "3 different slides lionhead area. One was very big the run out was 20 feet tall and quarter mile long"

Photo attached of a recent avalanche near Cooke, on the north face of Mt. Republic.  Steep, rocky, north facing.  Everything that I have been seeing the last 2 days has been similar:  steep, rocky north faces above tree line, often associated with wind loading, and cornices.  We observed 4 other similar avalanches yesterday, like the photo attached.  

Across the road from Bacon Rind at 7,070' on a west facing slope I saw a small skier triggered slide that ran into the Gallatin River. 

Skiers noted two slides in Divide Basin that occurred on high, steep, north facing slopes lTuesday night when the wind picked up.

Another party noted an avalanche near Blackmore: "We skied the ridge north of Blackmore (Tomahawk Ridge?) traveling between 6800' -9200' on SE-NE aspects. On the ridge above, ~9400' on a NE aspect there was a natural avalanche, maybe cornice failure, probably same timeframe as the Divide slides. ran ~600'. HS-N-D2-R2-O"

From Obs, "Noticed this large avalanche in unsupported terrain yesterday morning. I called it HS-N-R3-D3-U although it looks to have failed on facets at the ground. Frequent flyer but impressive. Debris was approx. the size of a football field and 8-10' deep, ran full extent of D3 track.

We dug on a nearby slope. 8050', E/SE, 29 deg. HS 200cm, N/O interface down 40cm. 1cm MFcr with small grained facets above and below. Fair structure, no prop. A bit of grapple mixed in new snow and todays solar input was not warm enough to soften current surf. crust"

We saw 6 natural avalanches on our ride in Lionhead. They all involved snow in the last week or two. On our exit we ran into who a group that witnessed a sledder triggering this slope. It was about 3 feet deep and was clearly wind loaded. Luckily he was not caught. When folks are triggering slides we know other slopes are also unstable. Be careful out there!

Our party experienced a sudden collapse while ascending, as we exited the trees above Olie’s Woods and began to cross a a meadow @9600’. The collapse was assumed to be at least 100’ wide, as we saw a small tree shake approx 100’ from the leader and our entire party felt the collapse. We dug a pit and got the following results:

HS 135

ECTP 17; 55cm down.

SP- Q1, Sudden Planar failure, entire block slid into pit

Failed on 2mm facets, 10 cm below an ice crust.

From IG, “Noticed a few natural and human triggered surface slides of the new snow on the old crust layer. All of these were north of Bridger Bowl on The Ramp”

A group of riders spotted a large natural avalanche on the north-face of Miller Mountain on Sunday that we believe occurred earlier in the day. The max crown depth is estimated at 4-5 feet and 300-400 feet wide with a 700 vertical foot run. 

From Obs, "While skiing Shafthouse Hill I intentionally trigger a wind slab on a small slope. The slab was actively forming with the new storm snow. I triggered it by ski cutting the slab at the rollover. It broke very easily and was approximately 15cm thick.

Aspect: SE

Slope angle: 36 degrees

Elevation: 8315’

Weather conditions @ 1130, overcast and moderate snowfall, 18 degrees F, winds SSE 15-20 mph."

Chunk of cornice fell off the top of Arden Peak. Notably the same aspect/elevation as the 2/27 observed natural slide on E face of Mt Bole but the cornice fall did not step down beyond the surface snow.

From obs: "On March 4th around 2:15 PM my partner and I observed a skier (of a separate party that was caught and carried) in a D2 R2 on the Lawnmower in the Absorkas. I believe the slide was released on a buried weak layer (We only observed the crown from a distance). The victim came to a stop approximately 1,200 ft below the start zone and was buried up to his neck. There were multiple tracks on the slope prior to the avalanche. My partner and I skied up to the separate party with the victim approximately 30 minutes after the event."

From another email "FYI big skier triggered avalanche on the lawn mower slide path on town hill today around 3pm. One skier caught and buried to neck and later airlifted out with leg injury. Our party arrived maybe 45 min after the slide and assisted others who were there."

(NE, HS, ASu, D3, R4)

We toured into Hyalite with the intention of skiing the North East Face of Hyalite Peak. Our primary concern was wind loading on leeward slopes. Before starting the day 6" of snow was reported in the Northern Gallatin range however we only found up to three inches of new snow. Approaching the saddle we found soft snow (2-3") on a pencil-hard crust. Once reaching the summit we descended carefully onto the NE face observing a shooting crack on a pocketed soft wind-slab after performing a ski cut. Noting this we descended further staying on the ridgeline. We then found a similar snowpack to the saddle with no cracking after a few more ski cuts and decided to ski one at a time down the duration of the face. Skier 1 skied a few turns down the face when a loud wumph was heard and the whole face started sliding. Skier 1 was caught, carried, and partially buried at the tail of the slide path. Skier 2 observed skier 1 and skied down to them after the avalanche stopped. Skier 1 was then fully dug out and both skiers left the avalanche path unharmed. The slide was thought to be (D3,R4) breaking all the way to the ground and spanning at least 500' wide.

Traveling into Blackmore Basin we assessed two potential lines from below that we had already planned to potentially ski.  We gained the saddle between Blackmore and Elephant. We observed snow transport from SW winds and noted the zone we were heading to might have wind loading occurring at the top. We traversed on scoured slopes by foot over to the entrance of the line that we intended to ski. Upon our arrival we noted a convexity of wind loaded snow on the skiers left of the start zone and made note to avoid it. We transitioned to skis and made a plan for skier 1 to enter traversing to the skiers right. Once skier 1 started traversing to the right, approximately 40 feet from skier 2,  a small collapse propagated at the ski tips of skier 1 across the entire entrance. Skier 1 yelled avalanche and was able to self arrest on the bed surface/ crown. After the slide occurred, we reassessed and felt comfortable descending on the bed surface to the toe of the debris, one at a time. We decided that was enough for one day and headed back to the trailhead. In retrospect, we underestimated the size of the potential wind slab and the danger of the high consequences terrain where a slide might not bury but potentially carry and kill a skier by taking them over cliffs. 

SS-ASu-R2-D1.5-I

Vertical Fall: ~700'

Distance Traveled: ~1000'

Aspect: 15 N

Elevation of start zone: 9645'

From FB mesage: "Buck ridge. East facing slope. Beaver creek area. Sled triggered. No burials."

Here is a picture of an avalanche that occurred between Daisy and lulu road just off HWY 212 today. SE facing slope that was snowmobile triggered

From obs, "We observed another smaller natural avalanche on an exposed ridge below Miller Mtn, this looks to have been about 12in deep and probably occurred on the same layer as a larger natural avalanche. Both were on N or NNW facing slopes in areas with heavy wind deposition."

We believe this was a skier triggered avalanche on 3/2

From IG message 3/3/23: "Yesterday on March 2nd we were on the trail to daisy pass just before the bowl in cooke city. There were 12 of us of us no total. Just behind us a large avalanche came down covering the trail and clearing trees on the way. We went to investigate to make sure there were no burials when 2 skiers came down and said they were stomping on the facet layer and triggered it intentionally. The slide swept the skier’s parked snowmobile off trail and carried it about 100 feet."

From email 3/3/23: "We rode over [Daisy Pass] in the afternoon around 5pm and it hadn't been there when we went over the pass early that morning. We heard from a couple of other snowmobilers that some folks had been skiing up there, parked a sled at the bottom for their lap, then triggered the slide by ski cut before they dropped in. The slide buried their sled and they had to dig it out. Here's a few photos that I took that afternoon."

From email 3/3/23: "... Crown looks 5-6' deep, 150'+ wide and SW aspect. Here is a picture."

We observed a couple more natural avalanches on Miller Ridge today. NE aspects, around 9800'. 

On 3/1/23 at 11am we saw a very large avalanche crown on the east side on Henderson Mtn., in the big avalanche path off the highest summit. It likely occurred late yesterday or early this morning. There was minimal new or drifted snow covering it, and it was snowing and blowing yesterday all day.

I estimate the crown is 6-8 feet deep, possibly 10 feet in spots. Measured on GoogleEarth to be 700 feet wide. 1200 feet vertical. HS-N-R3-D3-O. It did not go to the ground. Given how much wind-loading this path gets it may have been near the interface the 6 feet of snow that fell over the last 7-10 days, but it easily could have broken on a variety of faceted layers deeper in the snowpack.

Today wind was very calm and skies were partly cloudy. We saw a few shots of blue sky mixed with a few snow showers that totaled maybe 2-3cm.

Pretty mild observations:  north ridge above Hebgen, some woomfing on the ridge pretty subtle.  This was yesterday morning, on the ridge top.  Tons of new snow.  Also point release in the slide area, north face of slide scare, above quake lake, visible from the road new in the last couple of days.  Obviously natural trigger there.  

A rider triggered an avalanche on a small slope in the Cabin Creek area.

A cornice collapse in Sage Basin triggered an avalanche on a wind-loaded slope. The avalanche broke down to an old layer of buried surface hoar at 150 cm height (total snow height - 255 cm). The average depth is difficult to discern because the crown abuts the cornice line. The avalanche depth as stated was measured in the flank in a snowpit profile. Avalanche width and vertical run are estimated using photographs and Google Earth. 

From USFS Snow Ranger Report: "We rode on Buck Ridge today to do some maintenance on our RAWS station for the fire folks and check on the yellow mule cabin.  Where the wind hadn't blown it away yet, there was 4" of snow from over night on top of very firm snow, likely from the last round of wind.  The most sheltered areas behind trees and down in the basins still had some deeper, soft snow and better riding.  We saw one small wind slab avalanche in the new snow above Beaver Creek on a north aspect."

We triggered and were caught in an avalanche very near town.  We skied the east side of Miller,  dropped down to descend the very eastern slope just above town. While standing on approximately a 30-35 degree slope we experienced a release immediately above us.  The crown line was approximately 18-24" and extended appx 50' across. We were caught for about 150' before coming to a stop and buried to the thigh. The entire slide was appx 400' from top to bottom.  It was appx a D2.

From email, "I think this natural avalanche happened about 24-48 hours ago.  (pretty sure it wasn't there 2-3 days ago?). It's an E, SE aspect, about 9200', between Cooke City and Silver Gate."

On 2/25/23 a group reported, "On the southwest ridge of Mineral Mountain we observed a large slide, approximately 200ft wide, that appeared to trigger another slide lower down on the slope."

On 2/26/23 the same group noted more recent natural avalanches near Republic Mtn.

On 2/26/23 a skier saw another natural avalanche near Sheep Creek. Large avalanche on a small slope.

Possible remote trigger by wildlife

From email 2/26/23: "I just talked with a fella that reported his buddy was buried up to his chest in an avalanche yesterday off of east abundance, near the cliffs. He reported a 4' crown and 200' wide. His buddy was snowmobiling."

From IG message 2/25/23: "Hey just wanted to report a Cooke city avalanche from today. Happened at 3pm caused by a skier coming down a south facing slope above Round Lake. Everyone was fine, he lost his skis and everyone learned"

Triggered wind slab in southern Gallatins

This natural avalanche was seen today on E. Henderson Bench.

A snowmobiler saw this natural avalanche hit the Daisy Pass road within 10 minutes of riding by. He did a beacon search on the debris to confirm no one had been caught. It occurred about noon. This path is not very visible from the bottom and is not one that runs regularly. It killed a rider who was on the road in February 2012. The accident report has good photos of the path from afar.

Wind-loading in the start zone was the likely trigger since skiers and sledders do not access it.

From an email: "The crown was hard to see, but only looked a few feet deep where I could see it, but the debris pile was 10'+ on the road."

A big thanks to Dan Wykoff for providing the story and pictures.

From Obs, "On Friday I noticed “Provo’s run” (large path near overlook mtn) slid from the top which appeared to have slid due to the heavy wind loading.  The slid looked to be about 24” deep and ran full path .  So today I checked out the west facing walls close the hyalite lake and around 9500’ the upper sections of these slid paths were wind effected and unstable, and I did not ride them 

I dug a pit around 9500’ on the west facing wall near the lake and got unstable results.  ECTP 11 which propagated below the recent wind load from last week.

the snow pack is 240 cm deep and is nice and consolidated without  any major layers on several of the pits I dug at several elevations on these upper elevation"

A group watched a natural avalanche from the Pilot Creek Parking area cascade down the mountainside on Friday, 2/24/23 at 5:00 PM. 

From IG. “I spotted a large crown this morning on the E face of Bole. The crown appeared to be pretty deep, at least a few feet, and propagated quite wide. It also looked like there was a debris path coming down the apron of the E face of Hyalite peak, but I was too far away to know for sure.”

From email 2/25/23: "... a good sized slab avalanche on Fan, NE Face. Crown height hard to estimate but looked like a 2’ or so. Maybe running on interface from when it got cold earlier in the week? Possibly deeper than that but sure could have loaded that much this week. Anyway- very white bed surface, good propagation, 200’ -300’ crown length, debris stopped on upper bench. D2.5. Likely triggered by cornice fall."

From IG: Skiers near Mt. Blackmore on 2/24 saw a large avalanche on the east side of Mt. Blackmore that appeared to have happened in the last 24 hours.

From IG message 2/24/23: HS-N-R2.5-D2-O. In emigrant gulch on an east aspect around 9k feet. Seemed to have stepped down on to a PWL, however it’s pretty tough to tell.

Came across this very large cornice that appeared to have broken naturally sometime in the past 24 hours. Saw a few others that had broken recently throughout our tour, but none as large as this.

Triggered a small 2’ deep wind slab in new snow this afternoon.  NNE aspect 9,500’, approximately 38° slope.  Riding was excellent on all high North facing slopes and this was the only sign of instability we saw all day.  Wind was howling on the way out, lots of snow coming out of the trees and transporting at ridge tops.

We rode to Round Lake, Goose Lake wilderness boundary and Lulu Pass. We saw a coulpe of small and very steep avalanches that released in the new snow. We dug 3 pits and got ECTX or ECTN28 on the new/old snow interface 2-3 feet under the surface. We were glad to not find propogation. Wind ramped up during the morning creating white-out conditions at time. At Lulu Pass we went to investigate wind slabs and got a collapse (whumf) when we stepped on it. Wind-loaded slopes are dangerous right now. Slopes ae actively loading and sensitive to triggering.

From email 2/26/23: "I had heard a rumor from snowmobilers that there was a human triggered avalanche on Lionhead on Thursday the 23^rd.  While in Taylor Fork yesterday, we ran into one of the individuals that was a part of the incident.... he and a buddy were climbing together and he uncovered a rock that his buddy then hit.  While the first rider continued to climb he triggered a slide, and it partially buried the second rider.  He was able to deploy his airbag, but was carried approximately 100 yds down slope where he was buried.  He was quickly found by other members of his group.  

As seen from the highway, Lamar Valley, SE aspect. Mid-morning today. -3°. 

In Cooke City a large storm dropped 4.5" of snow water equivalent (4 feet of snow) and there were a few avalanches reported during and immediately after the storm. We saw one large avalanche on a south facing slope on Meridian, and a smaller wind-loaded slope that avalanched on Mt. Abundance (photo). We saw no other activity. Our concern is the interface between the old snow and new snow. The avalanche activity seemed to break here and on slopes with a wind-load it's worth being extra careful.

Meridian: R2, D2.5 (likely last night, 2/22)
Abundance: R3, D1.5 (maybe on 2/21)

From an email:

Many collapses. HST 15cm. NSFing on the surface. Light winds out of the E, S.

Several small wind slab pockets in steep, wind loaded areas of terrain. This photo is the largest one that released. Bison, watch out!

On my drive back from the park, I noted a few others. Surprisingly, nothing on those S slopes around Meridian went.

-Old Man Rays, released mid slope, as well as a small pocket below the cliff in sympathy. SS-N-R2-D2-I(?)

-Miller Ridge, SW aspect at about 9500’, large crown. That’s all I could see.

Photos of some recent natural avalanches near Cooke City today attached.  All of the slides observed appeared to just involve new snow from the Feb. 20-21 storm.  (occuring on all aspects, but primarily on NE aspects)

New snow:  generally about 50-80cms of settled new snow from Feb. 20-21.

Quite a bit of collapsing experienced today while breaking trail, particularly in the lower elevations.  

Snowpit attached from a SE aspect at 8500'.  HS: 170.

ECTP15- 55cms down, at new/old interface.

_____________________________________

from 23 February email:

Residents of Silver-Gate caught a glimpse of a large natural avalanche south of Silver Gate on Wall Mountain. The size is uncertain, but it knocked down a stand of trees. Two people state that they believe they heard the avalanche in the pre-dawn hours. 

From IG: “Ski cut trigger. West facing. 9800ft. Big sky area.”

We rode through First and Second Yellowmule at Buck Ridge. There was a natural avalanche below the cornice line on the headwall above second Yellowmule that broke within the last 12 hours as it was not covered by any new snow. From a distance, it looked ~200' wide and broke 1-3' deep. I believe it failed under the storm snow, not of deeper weak layers.

From Marienthal Observation: "Drove up to Bridger at noon and saw a large avalanche on along the road north of the fire station. It was 75’ wide, 1-1.5’ deep and 25’ vertical. HS-N-R4-D1.5/2. It was on an east facing slope, south of the long slope that has cornices. The slope with cornices hadn’t slid at this point. On the way home at 3:30 the larger slope with cornices had slid. It was very big, possibly R5. 1.5-2’ deep, 200’ wide, huge chunks of hard slab and cornice. Looks like new wind-loaded snow with some gouges into older snow.

From Olson creek I had a cloud-free flat light view of the ridge from Saddle to Bridger Peak and looked with binoculars. There was a wind slab just north of quarter saddle that did not go over the cliffs. Probably 1-2’ deep, 30’ wide of new snow. There was a large wind slab on the north half of Between the Peaks (250’ wide) and one similar depth wind slab in the Pinnacles (100’ wide). Both of these broke 1-3’ deep immediately below the cornice and did not entrain much snow or propagate very wide or downslope given how much new snow there was. I could see the debris from the slide between the peaks which ran over 1000’ vertical to the top of the runout zone but relatively low volume."

From email, "At 12:45 p.m. I saw Climax run naturally. SS-N-R2-D2-I. The low visibility and distance made it hard to tell how deep the crown was, but based on there not being much volume of debris and it not running very far I’m guessing it was within the new snow/storm interface and didn’t step down to any buried PWL."

A snowmobiler triggered an avalanche on a wind-loaded slope near Mount Abundance and was carried downhill. The sled hit a tree but the rider was not buried or injured. 

Triggered a couple small slides on the cornices that typically form in the corridor here: 45.91263, -110.95506

wind was blowing in strong gusts and it started snowing very heavy around 1pm  

super reactive. Approached the small slope and the whole thing went. It was only 2-3 inches deep. Likely from wind blown today and some of what was falling. It did run for about 40-50 wide. Nothing that would bury a person but definitely a telling sign. 

About 34 degree rollover, 14 inch crown.

Riders north of Cooke City on 2/16/23 saw an avalanche that appeared to be recently snowmobile triggered on Crown Butte.

Saw debris and what looked like a crown line from a natural avalanche that probably happened a day or two ago in palace butte basin on a NE aspect above Arden lake. My best guess is 150ft wide crown, 1-2ft deep?

Airplane Bowl.

Small storm slab released on a small piece of terrain. East aspect around 9200.

Low winds/no snow transport when I was up there and the east face had little to no wind effect, probably 16-18in new snow. Saw this slide with about a 8-12in crown and 100ft wide on the north face, didn’t see any other activity aside from some small point releases on really steep east aspects.

From another party: Saw a sizable avalanche on the north east face of Blackmore, likely broke mid storm and was partly filled in already - estimated 20" deep, 100' wide. Had shooting cracks and collapsing while ascending northeast ridge. Hand pits showed planar results on an 8" harder slab beneath all the blower on top. 

We observed a few small crowns on steeper road cuts in Sourdough today, NW and W aspects. 4-8" at crown, 20-40' wide, ~10' vertical. They looked like storm slabs that had run overnight, maybe on a density change in the storm snow. Debris piles were small and covered with 2-3" of new snow. Low consequence, but maybe enough to surprise a kid or a dog. Photos were taken shortly above the 2 mile marker.

Was about 80% of the way up to the top of the middle meadow on history rock this morning when we remotely triggered a small avalanche from the skin track.  Slide was just new snow that had fallen within prior 24hrs.  Crown of about 8 inches, 20ish feet wide by 20 feet long.  Face that slid was east facing.  We took this as a sign to reconsider skiing something even as low key as history rock and decided to ski the skin track back.

[Dropped the pin for this observation exactly where I believe the observation to have occurred.  Took an OnX waypoint while out there to help too.]

In Beehive with AAI Pro 1. Storm snow measured at over 30 cm, roughly double what was reported at Big Sky/YC. 5% density. Wind Slabs slowly building from L to M N winds, both WS and Loose Dry touchy on all slopes steeper than 35 with a MFcr as the interface - basically everything W, S, E aspects below 9500 (probably above too but we didn't go that high). One skier triggered wind slab observed low in the "tyler's" slide path on a SW aspect, 8700 ft, 35 deg, SS-ASu-R1/D1-I. No evidence of active persistent slab, 11x pits @ 8500 SE, HS 170, ECTX for all.

Went for a ski up the Flanders drainage in Hyalite today. The day was punctuated by light winds and heavy snowfall.

On the skin in, we noted numerous D1 storm slab avalanches about 15cm down in the new snow on many aspects and elevations. Approaching a ridgeline, we experienced a shooting crack that propagated a very small slide in slightly wind affected snow. We dug an ECT on a SE facing aspect at 9000ft. We were unable to get propagation. Snow totals appeared to be higher than forecasted, with 60cm of new snow as of about 12:30. By the time we ripped skins, the area had received an additional 10cm of snow, putting totals around 60-70cm of low density snow on top of a stout melt freeze crust on the aspect we were skiing.
 

we did not observe any cracking collapsing or wumphing in buried weak layers, nor signs of avalanches on those layers. The new snow had very low SWE.

Just a little more than 4-7” snow in Hyalite this morning

I skied at Lick Creek area and there’s 18-24” and still dumping

Low density

In the meadows I skied (not the Main meadow - too far to break trail) snow is on pretty firm melt / freeze crust. Heard a few whumps skinning up

Also of note, as we traversed a corniced ridge later in the day, two of our group members simultaneously came too close to the edge of a cornice and it broke away, but did not fall down the slope. Fortunately, everyone was alright, but it was a close call and we will definitely be more mindful next time. We believe the cornice was made more sensitive by the warm weather over the past few days. 

On 2/12/23 Riders saw "Seemed to be a decent sized slide runoff was pretty deep where it stopped in the trees figured it was probably two days old. Southwest facing. Roughly 44.86695° N, 111.24123° W"

We also observed a most likely remote triggered small wind slab (not our tracks next to it). Solar aspects were hot. Top of snowpack was relatively stable in our 4 foot pit, some collapse but no propagation (E aspect, 8400 feet). 

2/10/23: Our group did a big loop - Daisy- wolverine- goose - sheep -lulu. Saw minimal wind transport except on high points ( see photo). After looking all day saw an R1D2 slide (see 2nd photo) on a ENE slope above 10,000' south of Lulu pass, unknown trigger, though the whole area around the slide had cornice growth. We observed a lot of tracks highmarking into windloaded alpine slopes but saw no rider triggered avalanches. 

On our 3rd lap on the North Side Burn in Sheep Creek, we traveled up the ridge to take a look at the steeper terrain to the west along the ridge. From our protected vantage point, we could see a recent wind slab that appeared to release naturally some in the past 24 hours. The crown was obscured, but I would code the avalanche as SS-N-R1-D1-S. The avalanche was approximately 3-6" deep, 25' wide, and ran for ~60'.

This afternoon my group of 4 was riding up out of Tepee Creek heading towards Cabin Creek and I set off this small slide on a northeast facing slope as I was coming down it. The slide broke about a foot deep on top of the packed layer of snow and was 150-200' wide at the crown. Thankfully it slid slowly, less than 100' and I was able to ride out of it. 

From FB: Had some tourists in the shop trigger an avalanche on two top yesterday. Didn't get exactly where or much details. Steep tracked up slope they set off. Just a partial sled burial.

One maybe two distinct seemingly natural large natural slab avalanches on small slope directly next to bridger canyon drive.  One on the lookers left was likely cornice triggered, but on the right it's unclear to me if it propagated or released naturally.

We rode up Yale Creek and into Mt Jefferson Bowl. Walking to the edge we triggered an avalanche (intentional) on a slope that was getting wind-loaded. It broke up to 1.5 feet deep, 250 feet wide and 50 feet vertical. The new wind drifts were sensitive to triggering and the slabs propagated wide. Weak layers at the old snow surface may have helped us remotely trigger the slope. The two things to look out for in the Centennials are weak layer of sugary snow or feathery surface hoar in the upper 3 feet of the snowpack and slopes that are freshly wind-loaded.

From FB: We saw a fresh break on the west face of sage peak last night, I would guess around 9500’.

We rode north of Round Lake this morning (2/6/23)....

There was a small snowmobiler triggered slide on a convex bench between Sheep Mtn. and Round Lake that was triggered this afternoon. It was 1.5-2' deep, 30' wide, and looked to have broke on a weak layer below last week's snow, on a freshly wind-loaded slope. In a relatively shallow, rocky area (photo attached).

Me and a buddy were out skiing/camping in the Hyalite Lake area. Late Saturday afternoon we started skinning up towards Hyalite Peak. The path up to the ridge was super hardpacked and windswept. We got up and there was quite a bit of snow loaded above the north slope. I dropped over the side and took about two turns before the entire face above me released from the very top and traveled down the entire north side down to the bowl below. I was able to get to the rocks on the side and my partner was able to pick his way down. The crown looked a few feet deep from what I could see and stretched across the entire top of the line.

Toured/ skied on S though E aspects between 6000' and 8200' and observed the following:

...

-Several localized whumphs 

...

-Stomped one freshly wind-loaded rollover on micro-terrain and released a small (15 cm - 30cm thick) windslab

Dug at South facing snowpit at 9700' near the base of a wind-loaded slope, ECTX HS:280. Continued on less than 200' up the slope, the skier breaking trail triggered the avalanche. The third skier in the group of five was caught, carried, and buried to the waist. The crown was 1-2' deep, and 50 feet wide. Location: South of Fisher Mountain. Yesterday triggered a small windslab on a north-facing slope on miller ridge, no one was involved. 

A 2’ storm snow avalanche in the Chippewa Notch area was apparently triggered by a rider. It propagated significantly across complex terrain, and ran through plenty of terrain traps/trauma trees.

We triggered this very small slide on a steep convex  rollover by mt abundance. South facing. Triggered from on top by snow bike. Was only 60’ wide and didn’t run far at all. About a foot deep.  Some impressive high mark tracks in the area. No other signs of instability today.

From FB message: I triggered this one Thursday night (2/2/23). Got lucky it didn't gain speed and sack on itself. Been in this zone 1000 times, never seen it slide, always gotta be on your game... NE aspect in Beaver Creek.

Big Sky Ski Patrol reported a skier triggered avalanche in "The Mullet" in the backcountry outside the ski resort boundaries. One skiers was reportedly caught and carried by the slide. The initial skier triggered slide also triggered another avalanche in the adjacent "Rattail" avalanche path. Details are second hand and specifics could not be confirmed due to low visibility.

Skiers reported getting several whumpfs in a thin snowpack in Specimen Creek.

Skiers northwest of Cooke City reported several collapses while they were breaking trail. 

A snowboarder noticed several small slides on the east-facing walls of the Main Fork of Hyalite Creek and a small slab avalanche in the back of the Divide Peak basin. 

From BBSP: "Most of the Football Field pulled with the top Bitter End shot."

As we rode into Lionhead we saw many slides that either ran naturally or from cornice falls (separate avalanche log record). Most of the slides happened Fri or Sat. Winds are blowing strong at all aspects and elevations. Slopes are being loaded further and we triggered a small slide (video) from 50 feet away (aka remotely triggered). This is a serious sign of instability and we were careful to not get on or underneath avalanche terrain.

As we rode into Lionhead we saw many slides that either ran naturally or from cornice falls. Most of the slides happened Fri or Sat. Winds are blowing strong at all aspects and elevations. Slopes are being loaded further and we triggered a small slide (video) from 50 feet away (aka remotely triggered)(separate avy log record). This is a serious sign of instability and we were careful to not get on or underneath avalanche terrain.

On Feb 11 we saw evidence of widespread activity that likely occurred during this cycle on 1/29-1/30.

Skiers observed a small avalanche triggered by a cornice collapse on an east-facing slope in Bear Basin. 

From Observation: "While driving to work from Ennis on Jack Creek Rd, I observed a natural avalanche occurring on an unnamed peak.  Approx location is 45 22' 57"N 111 28' 49"W at approx. 9000'"

Avalanche (possibly sled/human triggered) on an easy to northeast facing slope around 9300 feet.  There were lots of sled tracks on the slope, which is located just out of the wilderness at the far end of Buck Ridge.  Slide and sled tracks appeared to be from after the weekend storm and were covered with light snow from the last couple days.  Noted lots of wind transported snow along buck ridge this afternoon.

From Obs: "Went skiing up in Flanders area and saw several avalanches with crowns ranging from 1-3ft deep and running a several hundred yards wide. Also experienced two whumphs and some cracks on a wind-loaded aspect near the ridge"

Some photos of recent natural avalanche activity near Cooke City attached.  We observed about 10 slab avalanches today that ran during this cycle.

From text: "went up to Champagne Sherbet to ice climb but then there was a big fracture on the approach! Got to a safe spot and dug to see - a strange drifted wind slab over the old belay area has created a scary snow cave trap! We bailed out of there..."

On 2/4/23 we saw an old crown of a large avalanche from earlier in the week on the west side of Beehive Basin, on an east facing slope around 8,800'. R3-D2, 2-3 feet deep, 150' wide.

Riding north of Cooke City on 1/29 and 1/30, we observed many natural avalanches that occurred during last week's storm. Avalanches failed within the storm snow or on weak layers in the upper snowpack, on wind-loaded and non-wind-loaded slopes, and on all aspects. We observed avalanches on Crown Butte, Wolverine, Scotch Bonnet, Sheep Mountain, and near the wilderness boundary at Goose Lake.

Several avalanches in the Goose Lake area. Assuming they happened on Friday or Saturday. Photo: J. Mundt (Beartooth Powder Guides)

From obs. 1/29/23: Some photos of recent natural avalanche activity near Cooke City attached.  We observed about 10 slab avalanches today that ran during this cycle.

From obs 1/29/23: "Noticed multiple crowns while driving up to bridger bowl this morning. Most evident was wide crown line on saddle peak below the corniced ridge stretching from the summit towards football field. Another was an obvious crown on what I believe is Argentina Bowl south of Saddle peak. From a distance, this all looked like new snow crowns and didn’t seem like anything stepped down to our buried weak layers. East wind had an interesting effect on the ridgeline above bridger bowl."

BBSP noted on 1/29/23: "A crown on Saddle Peak could be seen in today's bright light.  It began at the football field, extended to the top of the peak and a flank was visible extending down the skyline.  A secondary pocket pulled on the north facing slope below the Going Home Chute.  On the west side St Lawrence pulled out wall to wall, and behind Mountain Mother had a crown that was more filled in on the south facing side that began about half way down.  Also, a crown was noted on the south facing ridge of Bradley's Meadows ridge below the cliffs."

From 1/30-2/4 we also noticed old crowns "Between the Peaks" on Saddle, in the Y-couloir on the West side of Saddle Peak and in Jones creek on the west side.

A couple naturals seen on S-SE aspects and a couple whomps. While we were going up. Stuck to low angle fun the rest of the day. 
Stay safe this cycle you guys!

From IG message: "Another one today. Back of buck creek. Triggered 100 yards above where I crossed below it in the safe zone, after I went by. No burials."

Multiple natural avalanches were seen on all aspects, all elevations near Woody Creek Cabin. Poor test scores (ECTP) in 4/6 pits, mostly beneath the snow that fell earlier this week, buried small grain facets and decomposing surface hoar.

While snowmobiling up Little Bear we witnessed this natural avalanche. There was 2-3' of new snow. 

Natural avalanches, very large below Chimney Rock by Daisy Pass. And north side of Crown Butte observed on 1/28/23

On 1/29/23 GNFAC forecasters saw many more recent avalanches.

Photo of Castle/Submarine on woody ridge.  This all slid today.  Looked like all chutes along this face and south slid.  Also east facing Republic ridge several slides above rock band.  We skied woody west face to 9500 feet.  Wind effected snow. Top 2 feet  hollow.   Not bonded to older snow.  30 degrees.   Skied down short of objective 

We rode to the Taylor Fork weather station (near Pika Point on the rim of Sunlight Basin) and noticed a few slides along the way. At the weather station we could see that the north end of the basin natural avalanched: the slopes from where the cornices end in Sunlight Basin past Pika Point. It broke up to 2.5 feet deep on an old layer of facets and surface hoar. The slide was R2 D2, 3-400 feet vertical and at least 750 feet wide. It was a large Hard Slab. We spent time at the crown digging, making a movie and getting cold. No surprises, just great to see a real avalanche. We also saw smaller slides looking west from the station, close by. Afterward, we rode to the Sage/Carrot divide in deep snow; hero riding. Skyline Ridge was obscured in clouds.

On the drive back to Bozeman we could see many slides on road cuts and on slopes across the river; low elevation avalanches that we don’t get to see often.

The avalanche recorded in this form is the one in Sunlight Basin that we made the movie about.

On 2/4/23 we toured up the ridge between Going Home Chute and Tyler's (below prayer flags). We saw evidence of a large avalanche that broke during the avalanche warning last weekend in Going Home Chute, R3-D2.5 (see photos). It appeared to have run to the end of the runout zone and tipped over small trees.

From IG "Natural slide on southwest facing slope along Jack Creek Road in Moonlight Basin"

Took a drive up and around the Yellowstone Club and saw this slide today. I think that is Cedar Mt with Pioneer Ridge in front and to the left. Stay safe out there.

I was skinning up the ramp on Friday when I thought I heard a jet flying over in the clouds, but the sound stopped instantly. I assumed that I heard an avalanche, but was solo on the ramp and had no desire to go that way for a better look.  It was snowing and foggy. Today a friend said she could see a crown on the north side of Wolverine bowl that appeared to be 4 feet. With all that water, I thought something would go deeper, eh?