Trip Planning for Cooke City Area

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

Skiers observed natural avalanche activity just outside the Cooke City advisory area in Yellowstone National Park on Monday. Photo: S Gill

Skiers observed natural avalanche activity just outside the Cooke City advisory area in Yellowstone National Park on Monday. Photo: S Gill

A group of riders snapped a photo of this avalanche on Sunday. The slide isn't huge but it would be highly consequential in the treed terrain were trauma is a real possibility. Photo: A. Bertolino

A group of snowmobilers reported triggering this small avalanche from the backside of the rollover on Sunday. Triggering an avalanche from a long distance away is a clear sign of an unstable snowpack. Photo: A. Bertolino

This natural avalanche occurred late on 2/6 or early 2/7, on the southeast side of Scotch Bonnet Mtn. 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

From Obs: "On the morning of Sunday February 6, a snowmobiler triggered a slide in new snow on the SW face of Sheep Mountain. The slide triggered remotely while the rider was lower on the slope and he was not caught (the visible track is not from the rider who triggered the slide, his track was buried in the debris field). The crown was about 18" deep and 75 feet wide and the slide and the slide ran about 250 feet." Photo: C Mozol

Skiers observed several slab avalanches on the east face of Woody Ridge. They broke about 12" deep on a weak layer buried by recent snow. Photo: B Zavora

Skiers observed several slab avalanches on the east face of Woody Ridge. They broke about 12" deep on a weak layer buried by recent snow. Photo: B Zavora

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

Small natural slides on 2/6/22 near Cooke City. @coldfear

From obs 2/6/22: "Small natural soft slab avalanche on a SE aspect at 8737'... Crown was 20cm deep and  approximately 15m wide... Around 10am"

We saw this natural avalanche on Feb 6, 2022 on the north side of Miller Mtn. near Cooke City. It appears to have broke near the end of the 10-14" snow storm that fell the prior day (2/5). Photo: GNFAC

On Feb 6, 2022 we rode north of Cooke City and found 10-14" of new snow and a layer of buried weak facets that created unstable conditions. This setup makes avalanches possible to trigger on steep slopes. In this pit we had an ECTP13 break on weak facets a couple inches below the new snow. Photo: GNFAC

From obs (2/4/22): "…the last 2 days was finding buried surface hoar in many locations, up to 10'000'..... And we also observed a fresh avalanche yesterday on the NW aspect of Meridian Peak.  I couldn't discern a crown, due to our vantage point and a low cloud, but the debris pile looked relatively deep, and 12-48 hours fresh. Also, we had one significant collapse today on a mid elevation east aspect.  A slope with just a touch of wind deposit. (first collapse I've had in months!) The snow that collapsed appeared to be about 30-40' wide.  And a hasty pit showed the layer of concern to be buried SH." Photo: B. Fredlund

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

From email on 1/22/22: "This morning (20220122) I was ascending a steep North facing couloir up the N summit of Republic Mountain and on ascent (boot packing) about 1/2 way up the line I triggered a small soft slab from that propagated around the rock I was tucked behind, 40M above me and and 20M across. Luckily, my ascent line was sheltered from any above exposure and I was not caught or carried in anyway. The crown ranged from 8cm where I triggered it to an estimated 25cm at its deepest. The avalanche ran an estimated 200M. I believe the windslab ran on 1-3mm NSF's (evident on the bed surface) formed in the high pressure before the recent light precip."

From email 1/22/22: "Several dry loose naturals on Climax in steep terrain. Perhaps from Thursday or Friday?" Photo: N. Hance

Snowmobilers observed several small, dry loose avalanches in the new snow on Crown Butte on 1/21/22. Photo: R. DeSilva

Snowmobilers observed small, naturally triggered avalanches on Crown Butte. This avalanche occurred in the new snow on a wind-loaded slope. Photo: R. DeSilva

Observers noted very small, skier-triggered avalanches in the new snow on Chimney Rock. Photo: R. DeSilva

On January 18, 2022 a weak layer of surface hoar was buried by 1-2" of new snow near Cooke City. As more snow builds a slab over this weak layer it will cause avalanches. Photo: GNFAC

On January 18, 2022 a weak layer of surface hoar was buried by 1-2" of new snow near Cooke City. As more snow builds a slab over this weak layer it will cause avalanches. Photo: GNFAC

We saw surface hoar on all aspects near Cooke City on January 16, 2022. Photo: GNFAC

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

A cornice collapse likely triggered this large natural avalanche on 27 Dec 2021. The crown was 4-6' deep. Photo: S. Culotta

From obs: 1/8/22: "...One minor avalanche observed in Republic Creek.  It was on a steep and rocky E, NE aspect around 9700'..." Photo: B. Fredlund

From obs: 1/8/22: "Observed natural north Scotch Bonnet". Ran during storm 1/6-1/8. Photo: D. Wycoff

Large, deep avalanche on East face of Mt. Abundance. Photo from 1/2/22: S. Strenge

Large, deep avalanche on East face of Mt. Abundance. Photo from 1/2/22: S. Strenge

Large, deep avalanche on East face of Mt. Abundance. Photo from 1/2/22: S. Strenge

Snomobilers observed this natural avalanche on a NE aspect on Sheep Mountain on 1/1/22. It appeared to be more than 48 hours old. Photo: J. Fritz

This photo shows where people and their machines were buried. Photo: S. Strenge

Upper portion of the fatal avalanche on Scotch Bonnet. 12/28/21

Photo: GNFAC

Crown of the fatal avalanche on Scotch Bonnet. 12/28/21.

Photo: GNFAC