Avalanche Activity

From email: "Maiden Voyage to Goose Lake for the season today. Lots of wind drifted snow everywhere and challenging riding conditions. Performed Stability test on shoulder of Mount Fox NE facing slope at 10,300'. HS 180cm. ECTP2 40cm down on Buried Surface Hoar. ECTP 23 90cm down on MFcr with 1-2mm Facets. Saw several recent wind slab avalanches in steeper windloaded terrrain around Goose Lake, but limited activity was seen on Henderson. Lots of co/cr while touring on Mount Fox. D2 avalanche on east facing Mount Fox that appears to be on the SH layer, triggered by a cornice drop." 

Ob1: Photos 1-4, GNFAC

We rode out to Lulu Pass to look at the few avalanches that were reported yesterday on Henderson and Fisher Mtn. Today we did not see any avalanches that weren't previously reported, other than one small, but thick wind slab on south facing slope of Scotch Bonnet (photo). At least the avalanche on Fisher and one on Henderson broke near the ground (pics attached). Some slides were heavily refilled by drifted snow, so it was hard to tell how deep they broke.

Yesterday I saw a wide slab avalanche up on west Woody Ridge from town (photo attached). It happened late on Wednesday or overnight during or after the strong winds and snowfall.

Ob 2: B Fredlund, Photos 5-13

Quite a few natural avalanches observed north of Cooke City today.   Photos attached of:

5:  NE facing, 10,000, Miller Ridge

6:  E facing, 9900', Bull of the Woods Pass

7:  NE facing, 9700', Miller Ridge

8:  E facing, 10,200' Scotch Bonnet Mtn.

9:  E facing, 10,000 Mt. Henderson

10-12: NE- N facing, 10,000' Mt. Henderson

13:  NE facing, 10,000' Sheep Creek.

Observed from Flanders this morning. Presumed recent natural slide around ~9950 ft. on a E/NE aspect. Hard to tell from a distance, but cornice interference and/or wind loading are possible culprits. Poor image quality, but there may be more debris piles along the ridgeline to the south.

From the top of The Throne, we got eyes on two avalanches that occurred naturally during the major wind event yesterday in the bowl south of Naya Nuki. The largest of which was a R2-D1.5 that broke in the new snow in the main part of the bowl. The second avalanche (R1-D1) broke off the ridge near the summit of Naya Nuki and ran 150'. 

There was a natural avalanche on Saddle Peak on Wednesday, December 18. Strong winds ripped through new snow and loaded many slopes. The avalanche broke an estimated 250 feet wide, 1-3 feet deep, and ran 1500 vertical feet.

HS-ASr-R1-D1-I

Fraizer Basin, 8500', North facing, 35-37 degree slope, 1pm

30' wide, 6'' deep, ran 150', In the love chutes, Fraizer Basin 

1Finger wind slab sitting on a 4Finger hardness break.  Triggered from 30' above the crown, ran slowly.  A majority of the slab rode back up on the surface 50' below the crown.  Bed surface felt like small grained facets under skis, didn't look too close. Small and localized cracks and collapses were felt and seen throughout the day in the same location. 

Lots of wind slabs south of Cooke today. Strong wind all day and lots of blowing snow. 

Small natural windslab under the cornice on the Beehive Ridgeline around noon on 12/18. It broke up to around a foot deep, 20 ft wide, and ran about 15 vertical feet.

As we entered non wind-effected, upper-elevation terrain on Henderson, we consistently triggered many localized collapses and heard audible whumpfs. 

We remotely triggered a slide in upper Bear Creek that broke approximately 200 ft away in a gully. It failed ~18" deep on facets underneath the snow that has accumulated since Sunday. It broke in several pockets, totaling around 200 ft wide. There was 12" of new snow at the crown, with 0.7" SWE. The slab contained 1.4" SWE total (which accumulated since Sunday). 

Triggered a small slide (r2 d2) in a north east facing chute at around 8300 ft. The slide was triggered on a ski cut through a wind loaded drift and propagated about 15 or 20 ft wide. It about 6 in deep on the edges and two feet in the loaded area. We observed several other signs of instability throughout the day, most wind loaded terrain was touchy and easy to rip off with slabs anywhere from 6 in deep to two or three feet deep. All signs of instability originated from the interface between the new snow from the last few days and facets from the last high pressure system. 

The clouds broke briefly around noon today in Cooke City. It looks like the Fin slide naturally in the past day or so (12/15 or 12/16). It looks like two sections of the face slid, one from the top, and one lower and to the right in the photo. 

We saw two avalanches while riding along Buck Ridge on 12/17. These likely broke overnight on 12/16. One was a storm slab avalanche on the far (southwest) side of Buck Creek - broke 2-300 ft wide and ran ~500 vertical feet. The other was a similar, but smaller slide in 3rd Yellowmule (~100 ft wide and ran ~200 vertical ft).

From FB messenger: “Bottom of Slats area. Buck ridge. 
NE slope/hole wind loaded. Sled triggered, 315 pm Sunday Dec 15, 2024”

From Bridger Bowl: "On December 15th, 2024 at 12:09 p.m., a skier in open terrain was caught and buried by an avalanche in the Papa Bear region below Bridger Gully. The skier, who was with a partner, was buried just below the snow surface and was able to punch a hole up through the top of the snow. The skier's partner and other members of the skiing public responded quickly and were able to extricate the uninjured skier.

Although rare, inbounds avalanches may happen and are defined in the skier's responsibility code as an inherent risk of skiing, even within ski area boundaries. We share this as a reminder of the importance of skiing and riding with a partner, especially in deep snow conditions."

Notes about snowpack:

Slide was 8 inches deep, 450 feet wide, and broke within the storm snow 2 inches above the new snow/old snow interface. Trigger unknown.

The Alpine weather station received 2.5" snow = 0.2" SWE from 2200 on 12/14 to 0300 on 12/15, then intense snowfall from 0700 to 1200 added 7" and 1"SWE for a storm total of 9.5"=1.2"SWE over 14 hours as of noon.

These avalanches were reported yesterday 12/15 by ski patrol who heard them run and saw debris around 1230. They broke naturally towards the end of a period of heavy snowfall that totaled 10"=1.22" SWE. Photos taken 12/16 at 1045-1100.

from @brendan_durrum_photo

From IG: "Storm slab broke about 200’ above us as skinning up the hallway coming from the north side on the throne." 

Sunday morning 12/15 we were skiing just Southwest of Henderson Mountain between the road cuts. The first skier in our party remotely triggered this slide from a slightly lower angle aspect about 50 ft to the skiers left of the slide where the snowpack was shallower. It broke on a convex rollover about 100 ft wide and ran about 80 ft. downslope. The crown averaged 30 inches and broke on sugary facets about 18 inches from the ground. No one was caught.

I observed a large whoomph about 150ft from the ridge (top of glades) going up Blackmore today while breaking trail. was definitely wind loaded area… I could feel the energy in the snowpack today once I got up higher, super sensitive it seems. ECTN 14 in my pit I dug lower down the meadow with no wind slab prevalent.

Skied into middle basin from Beehive this morning and found 8-12 inches of unconsolidated snow on top of a sun crust. While skinning back up to the Beehive/Middle ridge we remotely triggered 12 inches of storm snow on a SE facing gully from 15 ft away, the crown was ~50 ft long. ~8,200 ft. 

Winds increased throughout the morning, actively loading E aspects. 

When skiing into middle basin, I stopped at the top of a convex roller and had cracks shooting out 50 feet in either direction from what seemed to be a soft slab in the new snow that slid about a foot or so. This was the most major sign of instability from the day. Lots of shooting cracks when skiing and skinning in the new snow. 

Small windslab triggered on approach for inspection. Failure interface had 5 mm Surface Hoar. Soft slab, remote propagation onto the adjacent slope. Debris covered about half of the road bed.

Gusty winds transporting snow in Taylor Fork on Saturday. Triggered a 4-5 inch deep wind slab that propagated about 50 ft at the top of a north east facing slope at 9,500 ft.

Noticed this natural avalanche on 12/8. East facing slope, ~9500 feet, Hayden Creek above Ripcurl area 

On 12/4, from the junction of Buck Ridge and Third Yellow Mule, we observed one small loose-wet avalanche (R1 D1) on a S facing aspect on Eglise Rock that likely broke in the last day or two of hot temperatures. 

Natural loose wet avalanche

From BSSP "On steep solar aspects, the surface snow became unstable and low-volume slides ran.
Point releases would entrain the top 3-4”, running on firmer layers below."

On Sunday, an R2-D2 wet snow avalanche broke out of the run Close Call within the boundaries of Bridger Bowl. This is a rocky, south-facing run. The slide ran ~650 vertical feet. The width of the chute constrained it, but it broke about 20 feet wide. 

From obs 12/1: "A decent sized loose/ wet D1.5 came down between laps (probably 1300) in what i believe is called gangstas. South facing, steep, thin and rocky. "

"The head of Beaver Creek was scoured nearly to dirt and the cornice is quite large there already.  We noted one small wind slab avalanche just below it.  We found a similar avalanche in Second Yellowmule that again appeared to be from wind loading.  Both appeared to be several days old.  We dug a quick pit on a north facing slope in Second Yellowmule and had an ECTN in 85cm of snow.  Only the bottom 5cm or so of that pit were sugary and faceted. "

A skier near Going Home Chute in Beehive Basin triggered a small avalanche in steep terrain that broke 20 feet wide and ran 100 feet downslope over rocks. 

From obs: "Intentionally triggered on a ski cut. Broke about 1 foot deep and 10 feet wide, ran on a hard compact surface below the soft wind slab." 

Hard wind slab likely on facets happened naturally maybe last week around Thanksgiving or just after. It is typically heavily wind loaded spot and was probably triggered by cornice fall. 

Big Sky Ski Patrol triggered a deep slide in the Big Couloir during avalanche mitigation work on 11/28/24: "Summit north peeled the cornice way back to the ridge and took out the upper hanging snowfield before crashing into the Couloir, leaving a 5-6’ tall crown in the chute above the dogleg."

Dave and I toured into Blackmore basin today and skinned up the SE shoulder to the ridge. As we entered the basin, we immediately noticed several natural loose snow avalanches (R1 D1) in steep rocky sections of the direct E face. These looked to have occurred in the last 12 hours, and though they would not have buried someone, they would have strained one through some nasty trees and cliffs.

Big Sky Ski Patrol triggered this avalanche during mitigation work in The Wave on 11/26/24... "2-3' deep on an ice crust just above the ground with a 2# shot in the Upper rodeo. Volume was limited as most of the snow was loaded just underneath the cornice, but still produced a sizeable size 2... Other paths in the Lenin region ran meaty wind slabs, full track with no significant step downs." Photo: BSSP

From email: "Northerly facing terrain harbors October snow, which has faceted. It is holding up plenty of dense snow and wind slab from the quite snowy and windy November. It was unable to hold the additional weight of a human trigger, and two pockets failed at the ground, which produced avalanches. Crown height maxed at 2’. Notably, where it did not avalanche, the failure propagated hundreds of feet down the ridge. It is a good data point- northerly aspects near tree line have potential instability."

Driving up Bridger Canyon this morning, we noted several natural avalanches in wind loaded terrain on Saddle Peak, the Football Field, and in Mundy’s Bowl. All The avalanches seems to be a similar wind slab problem. They broke just below the cornice line. From a distance and considering yesterday’s new snow, I would guess a foot deep or so (R2, D2, I)

Wind was ripping on the ridge and creating hard wind slabs 3-6” in depth. Without much new snow to transport they weren’t very large or widespread, but we got cracking and propagation on a steeper terrain feature (Hidden) near the ridge that led to us skiing a different line. The slab development was also found in isolated areas further down from the ridge in cross loaded gullies, but slabs were isolated to breaking at the skis. 

Localized collapsing and cracking yesterday on the upper slopes of Mt. Henderson, SW aspects.  HS ranged from about 30-75cms. 

From obs: "With the inversion and warmer temperatures yesterday, we (group of 3) discovered a super saturated, cohesive snowpack in Hyalite on the approach to High Fidelity. On the first pitch, I narrowly avoided a point release wet loose, probably around D1-1.5. After this we decided to bail. On the rappel, my partner narrowly avoided another wet loose, which he estimated to be D1.5 and deep enough to bury a person past their chest. The sun was not out but the mountains were shedding and there was evidence of warming and wind, because the trees had no snow on them. We were able to make ~2.5 feet in diameter “cinnamon rolls” by rolling a snowball downhill. If you’re going to any of the more exposed climbs in Hyalite, be very mindful of overhead hazards and wet loose problems which you would not expect this time of year." 

Skiers triggered several very thin avalanches in the northern Bridger Range on 11/21/24. They broke only a couple inches deep on windloaded slopes, mostly in north facing couloirs. 

Party of three made our way into Beehive Basin up to near the bottom of 4th of July Couloir. Noted strong winds blowing from the south southwest (up the canyon) Saw shooting cracks up to 8 feet out skinning up a boulder pile on a east facing aspect, (picture my friend took). Snowpack still to shallow to confidently ski any of the upper couloirs. Further down in the canyon on the short grassier slopes snowpack was reasonably dense and stable with a weak crust layer under 8-10 inches of the light fluffy stuff, snow depth up to 2 feet in select spots. Friend reported hearing one small whumph breaking trail up to the ridge on a convex roll. Skied out the entire slope with 10ish other people and didn't see any other signs of instability.

A small avalanche released in the northern bridger range on Sunday.

We skied hidden gully that had small storm slabs that propagated at our ski tips and only ~3inches in depth. 

On 20241107 I observed a small natural avalanche from the top of the PK lift at Bridger Bowl. The slide occurred  near the Slushman’s lift on a NNE aspect. It started as a small release in the upper start zone and entrained much of the snow in the couloir down to the ground. L-N-D1.5- G. 

Avalanche occurred after the start zone had come into the sun for a few minutes. The rest of the path was in the shade.

Wind speed at 11am 24mph gusting to 28mph on Bridger Ridge. Sky Clear. Temp 26F.

It was a relatively small slide but had enough power to carry a skier or rider through some very nasty terrain. Similar aspect and elevation to the Super Couloir slide. 

From obs: "I made it up to an old crown in a north-facing chute around Fairy Lake at around 9400 ft; it broke the night of 11/6 or the morning of 11/7. It looked like a wind slab that broke on a rotten layer of facets intermixed with scree. Found facets to be fairly widespread through the bottom of the snowpack on the north-facing slopes and surface hoar on most nonsolar slopes." 

From IG message: "Hey the post of super jogged my memory to send you this, a friend and I had whumpfing and cracks while skinning up the trees in the apron yesterday [11/6], we dug a pit and got an ect 4 collapse against the rocks. We were about halfway up the apron when we took this."

From obs 11/6/24: "Saw debris from several small natural avalanches below the ridge on an east aspect south of saddle peak while driving up to bridger. Most looked like point releases but there was one that might have been a small slab. Unsure because the light wasn't right to tell if there was a crown.

We stayed low but found a pretty uniform snowpack other than a couple of spots with sun crusts.

There was also tons of snow blowing over the ridge when we left around 3pm."

From IG Message: “Hey guys - my partner broke off a small avalanche in super couloir today… broke full depth across half the couloir, 2-3’ deep/20’ wide and looked like it ran around 500’. No one was caught. He might message you with pictures too but here’s a video from the top”

From IG Message: “Skier triggered Pocket in super couloir. Wasn't very unexpected, the skiers left side felt a little slabbier than the skiers right and tried to stay off it but got blinded by a sick face shot. Triggered going over a sharky rock spot, not very fast moving and easy to ski out of. Snow depth was 2-2.5 feet”

Avalanche observed on Chico Baldy above Mill Creek in Paradise Valley.  East aspect at about 9400'. Possibly a wind slab but hard to tell

Triggered a small wind slab:

-9600'

-N aspect on the NW ridge of Sphinx Mountain 

-Strong SW wind

-Noticed other small crowns, likely triggered from another party traversing the north-facing bowl at similar elevations