Trip Planning for Bridgers

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Chris Hericks, snow ranger on Beaverhead Deerlodge NF, points to the lower of two surface hoar layers. We are finding similar layering throughout our entire forecast area. The top 18" of the snowpack is weak and will quickly become unstable when it snows. Photo: GNFAC

The crown is not visible (it is down and right) but the X marks the approximate spot the rider was found. Photo: GNFAC

The crown was measured 4-11 inches deep and 75 feet wide. Photo: GNFAC

Looking at a weak layer of facets that the avalanche propagated on. Photo: GNFAC

Looking at the crown from below. Photo: GNFAC

On Sunday, February 6, Gallatin Country Sheriff Search and Rescue and the GNFAC responded to a avalanche in Lionhead. A snowmobiler was killed on a small steep slope when a shallow avalanche carried him into a terrain trap of trees. Photo: GNFAC

From obs 2/5/22: "We were planning on skiing ainger basin area. Snow seemed safe while we were skinning, but we dug 3 pits because the wind was so strong. got semi-unstable results each time, ect 12 to 18 with clean propagation around 4 to 9 inches down, depending on the slope."

This morning while ascending a line on Sawtooth Mountain (Lower Novocain) we triggered an avalanche (ASu-SS-R2-D2-O)  that caught and carried my partner an estimated 180M and partially buried him. His leg and hand were unburied and excavation of the head was done in less than 2 minutes of the incident. The avalanche only involved new snow from the last 48hrs and was triggered on a MF crust/facet combo 30cm down(formed 1/30/22). The avalanche was 30cm at its deepest and 20-30M wide and ran 250M. We were lucky to find both skis and poles a little ways downslope. No injuries were sustained.

We both agree that we were trying to outsmart the instability that was present on steeper S facing terrain and should have turned around much sooner, we were very lucky. There was 30+cm HST in favored areas and the high winds from 1/31/22 formed some sensitive windslabs in specific areas. 

Graph of Snow Water Equivalent (SWE) at SNOTEL sites in the GNFAC forecast area from October 1, 2021 to January 30, 2022. It highlights the extended dry conditions in January that contributed to weak layers forming at the top of the snowpack. GNFAC

Natural and skier triggered 2" deep loose snow avalanches in Argentina Bowl south of Saddle Peak on 1/27/22. There is also an older cornice break visible that gouged the slope below 1-2' deep, but did not break out a wider avalanche. Photo: GNFAC

Old debris from an avalanche that broke on the night of 1/25 or earlier. The crown is obscured by clouds and drifted in. Our tracks are visible crossing the bed surface up high. Photo: GNFAC

Snowpit in the crown of an avalanche on the south summit of Saddle Peak. It broke on 1/25/22 or earlier, 6-8" deep, 1,000' wide, hard slab on weak faceted snow. Photo: GNFAC

We saw this avalanche on 1/26/22 on the south summit of Saddle, and extending across the bowl Between the Peaks. Photo: GNFAC

This is the location where the skier came to a stop after being caught and carried by a small avalanche in the Bridger Range.

From Obs: "While skiing the playground, a northeast aspect off the Bridgers, my friends and I released a wind slab. The slab released on a rollover and was approximately 20 ft wide and 6-12" deep at the top. The slide carried my friend about 150 ft." Photo: Anonymous

The crown of a small avalanche that caught and carried a skier in the Bridger Range on Sunday. 

From Obs: "While skiing the playground, a northeast aspect off the Bridgers, my friends and I released a wind slab. The slab released on a rollover and was approximately 20 ft wide and 6-12" deep at the top. The slide carried my friend about 150 ft." Photo: Anonymous

The track of a small avalanche that caught and carried a skier in the Bridger Range on Sunday. 

From Obs: "While skiing the playground, a northeast aspect in the Bridgers, my friends and I released a wind slab. The slab released on a rollover and was approximately 20 ft wide and 6-12" deep at the top. The slide carried my friend about 150 ft." Photo: Anonymous

A snowmobile triggered wind slab on small slope in the northern Bridgers on 1/22/22. 

A group in the Wolverine Cirque noted several small wet loose avalanches that occurred during recent warm weather. 

A view of Sacajewea Peak from the Fairy Lake road. Evidence of winds are seen on the right shoulder of the peak. Photo: GNFAC

Slopes on Hardscabble Peak in the northern Bridger Range show bare slopes that got blown clean by wind. Photo: GNFAC

In the northern Bridger Range we dug a pit at 8700 feet on a north facing slope before skiing the chute into the basin. Our stability tests did not break and all evidence pointed to a LOW danger. Photo: GNFAC

Settlement rings around the base of trees near Cooke City, January 15, 2022. Photo: B. Fredlund

Natural avalanche near Fairy Lake. Observed 1/13/22, likely broke several days prior. Photo: N. Crews

Looking up at the Fat Maid from Maid of the Mist basin. Strong winds over the last week have scoured the alpine, exposing lots of rock. Photo: GNFAC

Strong wind over the last week created this surface texture in the Bridger Range. Photo: T. Allen

From email 1/9/22: "Skier triggered cornice failure avalanche. Broke at skis 10-12 feet from the lip. No one caught or injured."

From email 1/9/22: "Skier triggered cornice failure avalanche. Broke at skis 10-12 feet from the lip. No one caught or injured."

It was easy to crack the thin wind slabs that formed from strong wind the last 2 days. They were not propagating, but cracking indicated potential instability on wind drifts. Photo: GNFAC

Strong wind in the previous 2 days sculpted the snow surface into waves of sastrugi. Photo: GNFAC

Wind in the last 2 days gusted 45-70 mph and stripped some starting zones down to dirt in Beehive Basin. Photo: GNFAC

A small skier triggered storm slab on the west side of the Bridgers. 1/6/22

Photo: P. Hinz

From email (1/6/22): "Skied the Throne today. New snow instabilities. Higher density snow falling on colder snow. Saw a hand full of naturals all running on the new snow old snow interface."

Photo: E. Knoff

From email (1/6/22): "Skied the Throne today. New snow instabilities. Higher density snow falling on colder snow. Saw a hand full of naturals all running on the new snow old snow interface."

Photo: E. Knoff

From obs: 01/01/22: "Saw a small slide come off the ridge. We dug a pit and the wind slab was 8 inches to a foot and a half. During our snow tests it consistently broke on the week layer around a foot deep." Photo: B. Paulson

From obs 1/1/22: "While skinning towards the ramp we witnessed what looked like a natural slide that started right around Pete’s Pinnacle which ran down along the boundary line about 1000 feet. Unknown trigger."

Strong ridgetop winds transported snow onto Saddle Peak creating unstable slabs on January 1st. Photo: GNFAC

Strong winds on 1/1/2022 formed fresh, soft drifts. These drifts broke and cracked easily, and slid on steep slopes. Photo: GNFAC

We saw this natural avalanche on the north summit of Saddle Peak on 1/1/2022. It is one of at least 4 natural avalanches that broke on wind-loaded slopes on Saddle Peak in the past 3-4 days. Recent snow and wind formed slabs over weak facets which makes large avalanches possible to trigger. Photo: BBSP

We saw this fresh natural avalanches near Saddle Peak on 1/1/2022. Recent snow and wind formed slabs over weak facets which makes large avalanches possible to trigger. Photo: GNFAC