Avalanche Activity

From an email:

"Natural slide on Northern wall of the Hourglass in Northern Bridgers. No tracks in or out. Crown looked to be 8-10” deep and 25-30ft wide."

This wind slab avalanche released as a result of an intentional ski cut. The initial slab that released triggered a larger slab that ran close to 2000 feet. From the skier:

"At around 12:30 I ski cut the top of a NE facing gully on Bridger Peak, roughly 35°. A hard slab broke 6”-12” deep, around 100’ wide. This broke a secondary slab on a NNE aspect adjacent to the first one, around 300’ wide. The slide ran through trees and a gully, traveling close to 2000’ vertical into some lower angle terrain. It broke on the layer of facets that formed last week during the cold weather."

This avalanche was around the corner from the snowpit we dug in 2nd Yellowmule. It looked as though it was triggered about the same time we were digging. The slide failed on near-surface facets that formed 10 days ago that are underneath a hard slab of wind-drifted snow.

Multiple natural wind slabs, likely triggered by cornice falls over the weekend.

Ski patrol triggered this avalanche at the Yellowsone Club on Sunday (12/16). "8400’, ENE facing, 36deg start zone that was about 120’ wide and ran vertically 200’. The crown was 1.5-2’, went to ground, and was a mostly faceted snowpack with a bit of wind effected snow in the top few inches. The slide was released from a 4lb air blast." -YCSP

A snowmobiler triggered this slide yesterday while sidehilling on the leeward side of a ridge. Estimated crown was about 50' wide and broke about 12-18” deep.

Strong winds created 12-18" thick wind drifts that collapsed on buried facets and surface hoar. We had one crack 30' wide as we left a snowpit.

Two obvious avalanches released naturally in the late morning while we were in the bowl. Upwards of 8" of new snow fell with winds gusting 30-40 mph from the west.

From an email:

• Triggered small windslab in SW facing gulley at 9000' approximately 6" by 20'wide
• No collapsing or cracking of the snowpack observed, other than the isolated wind slab.

From e-mail: "The wind picked up after noon today and we observed moderate amounts of blowing snow at and above tree line. My climbing partner and I were able to trigger a small loaded pocket between slot corner and curtains, 30 deg, NNW aspect, which failed 6 inches deep and 15 ft wide on diurnal facets (old snow surface). The slab didn't move much due to the stubborn angle..."

Skiers descending Imp Peak in the southern Madison Range triggered this small wind slab. This is bull's eye information that larger slides are possible on wind loaded slopes. 

A skier writes, "Lots of blowing snow with multiple natural avalanches occurring during the morning."

From e-mail: "We encountered very localized loading that easily fractured and propagated uphill on a south aspect (photos) then bailed on the E/NE facing run we had hoped to ski, due to a 12-18" slab at the top, obvious wind loading throughout the whole thing (9900'-10300'), and the aforementioned obvious signs of instability. When we turned around, another similar-sized (4-8" by 10-20') slide had occurred on the same aspect as the one we had triggered. Neither ran more than 100' or so."

From e-mail: "We bailed on plan A ( bigger couloir ) because of the visual signs of rapid wind loading. We proceeded to plan B and started getting shooting cracks on small convex rollers. We found a nice small test slope and remote triggered a decent fresh windslab. It was surprising the energy it ran with. We decided to bail on plan b and head home. Remote triggered another smaller wind slab turning around."

From e-mail: "triggered a small wet slide in the Going Home chute coming back into Beehive, and we observed another natural wet slide on a similar aspect that had occurred since we toured past in the morning. Wind was light or calm all day and wind effect was minimal even at ridgelines." 

Avalanche activity from new snow. Wind slabs 6-8" deep and loose snow avalanches. Natural and skier triggered. Reported in Hyalite, Beehive and Bridger Range.

From e-mail: "Today while skiing Bat Ears Couloir in Bear Basin we encountered fast moving 12" deep wind loaded sluff however, it didn't step down."

Second e-mail: "Upon entering the couloir I performed a ski cut and released an 8 inch deep slab that was about 12 feet wide that ran about 700 vertical. Then we skied the slide path down and safely returned into beehive by exiting down bear basin. "

From an email:

"We did observe a natural slide at around 8300ft that failed on the high pressure facets that formed prior to these last two shots of snow. It appears that it was triggered by a slough from steeper, rocky terrain above, the crown was about 14 inches deep and around 50ft wide, in complex rocky terrain. The debris pile was approx. 200cm deep, plenty deep to bury a person. We skied 35+ degree slopes and found excellent stability the day after the storm. "

From an email:

"Went up to Blackmore for a pre-Thanksgiving dinner walk yesterday.  Winds had moved a good bit of snow since Wednesday and I observed debris from several avalanches on the east face...Most of the slides were thin, probably fresh wind slabs failing on the latest batch of NSFs.  The largest slide had some pretty sizeable chunks of hard slab style debris in it."

From an email:

Today, at around 11am, my partner preformed a ski cut on the top of a gully. The area he cut was south facing and in direct sunlight. The slough from his cut gained momentum and formed a small avalanche that went down the entire gully and apron, taking all of the previous days snow with it. The avalanche went on the old snow sun-crust, and new snow interface. We ascended from the back and found very stable results in both our pits, although they were both high and north facing. No one was caught or injured.

I had already skied down part of the slope in another gully, that was entirely shaded, and produced no snow movement.

A snowmobiler triggered this small wind slab near Lulu pass outside of Cooke City. Wind loaded slopes are main avalanche concern across the advisory area. 

Strong winds in the Bridger Range formed dense slabs on leeward slopes. Yesterday, A skier north of Bridger Bowl triggered multiple wind slabs near the top of Wolverine Bowl. The skier turned around and chose a safer objective. Photo: S. Whitefields 

From BSSP: "The 1^st, 2^nd and 3^rd Fork had failed as a unit taking out all of the early November snow, failing on facets above the October crust.  It ran far, taking out some mature trees and depositing a wide swath of debris 6-10’ onto the Merriweather ski run.  It was estimated to be a Size 3.5."

Climbers triggered this very small wind slab on the way to a climb up Flanders in Hyalite (11/11). A tiny slide to a skier can be bad news for a climber since losing one's balance or getting pushed off a cliff can be deadly. From an email (edited):

Photo: S. Magro

From Instagram @chartierk:

"Careful out there this year! While we are lucky enough to have a mostly stable snowpack here in Southwest Montana, we did just find this little wind slab well below the ridge line in Middle Basin. Slowboarder was fine"

Ice climber triggered. From e-mail: "Was descending off of Zach Attack tonight and set off a small slab in the gully on the decent. This was about 100 meters below the start of pitch 1. Constant whipping winds and lots of new deposited snow likely caused the slab to form. Climber caused. Didn’t carry me as it was small. Would be wary of the mummy cooler gullies abover scepter as well."

"We triggered a large avalanche in the Cirque with a 5lb. shot dangled from the Tram.  The slide broke 3’ deep and took out the Dobies, Cron’s and part of the Ramp Shot avalanche paths.  Hard slab- 1F minus generally.  Storm slab from the past 8 days.  The slide ran on a crust that formed from the left over snow from mid- October that got warmed in the 3^rd week of October.  The weak layer was just a thin layer of lower density snow trapped under the hard slabs- didn’t seem to be particularly faceted. Some grauple. The crust is not very hard or slick, about 2cm thick, and crumbled easily in hand... The slide had good propagation and the crown was at least 300’ long- impressive debris pile." -Big Sky Ski Patrol

From the MSU Backcountry Club in Instagram:Warning! This is a current, fresh, crown in the northern Bridgers! Every aspect had a visible crown and avi debris! This crown was 56cm at it deepest and over 8 meters long. ECTP21@53 and CT24@54 on the overlying slab.

Avalanche happened around 1100hrs