Regional Conditions for Cooke City Area

Cornices on the back side of Sheep mtn are getting huge. Guessing well over 25ft. They are right above a play area to the west of Ovis lake, and round Round lake. Photo: R. DeSilva

This surface hoar crystal is almost 1.5 cm (each square is 2mm) and was the weak layer in a few avalanches on Buck Ridge (3/29/20). Photo: GNFAC

We saw this natural avalanche from afar. It was NE aspect and likely failed on a layer of surface hoar 1-1.5' deep. The Madison Valley is in the background. Photo: GNFAC

Sunday (3/29/20) skiers near Fairy Lake saw this cornice collapse that ran for quite a ways in October bowl. Photo: T. Gittins

From obs. (3/29/20): "Significant wind started building mid morning, forming even bigger cornices and wind loading many slopes. Noticed this slide on an East/Northeast aspect at the back of the bowl above Maid of the Mist creek, possibly triggered by cornice fall but unknown. Happened between 9:45am and 11:30am today, as at 9:30am it was not there, and when we returned to the spot around 11:30am the slide was visible." Photo: CP

From email on 3/27/2020 : "natural slab avalanche I observed today near Cooke City.  An easterly aspect around 9,400'.  I'd estimate the crown to be 2-3' deep and about 100' wide.  Looks like it was triggered by a cornice fall (2-3 days ago?)."

Photo: B. Fredlund

From obs: "Wind Loaded slope. 2ft Crown. 100ft wide. firm, crusty bed surface. The avalanche was released by a ski cut." Photo: Anonymous

Snowfall throughout the afternoon fluctuated between S1 - S5 (during brief squalls). The winds started out moderate and from the west but calmed by the last lap ~5 pm. The new snow (from last night/this morning) was fairly well bonded to the sun/melt-freeze crust below, but the storm came in subtly upside down. Today’s snowfall (accumulating ~3” while skiing between 1-530) was light. Right along the ridgeline, we triggered 4 predictable small storm slabs 4~6” deep on the upside-down storm snow from last night/this morning, but surprisingly not on the old crust. They were each 5-10m wide x 5m long and only ran ~5m vertically. Photo: Z Miller

This is a photo of a small roof avalanche near Island Park. Warming temperatures cause water to percolate through the snow which lubricates the sliding surface. Roof avalanches have injured and killed people in the past, just one more thing to worry about. Photo: M.E. 

Dave Zinn digs a hand pit along the ridge to assess how the new snow is sticking to the ice crust. Photo: GNFAC

Obs: "School bus size cornices over Easterly portions of Lionhead Ridge. It is hard to tell from the photo, but the largest cornices were about 20-25' tall. We dug a few pits on East Facing slopes between 9,000-9,500 ft with the worst result being an ECTN-21 however these Cornices are primed and ready to fall with the abundant sunshine and warming weather." Photo: JR

From e-mail: "Natural wet slides... caused us to back off our plan of heading that way and ski a north, shady aspect instead. On a southern aspect. 9000ft. 1:30pm. We dug a hasty pit and observed a weak layer about 1m down. The facets were beginning to round." Photo: K. Master

From IG post with #gnfacobs: "I triggered a small windslab, mid slope on the north face of Wilson. It was a a pretty stubborn slab that broke above me. Cross loaded from lookers right. 6-8” deep." Photo: B Gill

From IG post with #gnfacobs: "I triggered a small windslab, mid slope on the north face of Wilson. It was a a pretty stubborn slab that broke above me. Cross loaded from lookers right. 6-8” deep." Photo: B Gill

From south of Big Sky yesterday 3/17 about 9:00, just north of Buck Ridge at 8500'. Large surface hoar on northerly aspects. Photo: Spence

We dug near the top of Bacon Rind and found 155cm of snow. Our primary concern is with the upper snowpack. As it warms and wets we can expect an increase of avalanche activity on the ice crusts. Facets are still dry and soft at the bottom of the pack and I got this layer to break with an ECTP29. Photo: GNFAC

Small slab avalanche in the upper Republic Valley, a northeast aspect around 10,000'. Photo: B Fredlund

Snowmobile triggered avalanche near Lulu Pass. Photo: Anonymous 

Snowmobile triggered avalanche near Lulu Pass. Photo: Anonymous 

From e-mail on 3/15/20: "At around 1230pm today, everything that was steeper than 35 degrees in star Creek simultaneously slid on east, north, south aspects. Soft slab 6-12" in thickness. Prior to that, it had been snowing S5 for three hours." Photo: B. Zavora

Cornices are growing to immense sizes in Cooke City. Try to minimize your time underneath these monsters and stay far away from the edge if you are on ridge tops. Photo: GNFAC

Mike Thom, Gardiner District Ranger, stands in a 7-foot deep snowpit at 9900' on Woody Ridge to the south of Cooke City. We found wind-loading to be our primary concern. Facets were still present at the base of the snowpack, but they are stable for now. Photo: GNFAC

Strong wind stripped snow off many slopes above treeline. Photo: GNFAC

This naturally triggered avalanche likely happened Tuesday morning. Strong wind loaded slopes and made huge cornices. Photo: GNFAC

From e-mail: "...some wet loose avy activity observed today just west of Cooke City (south aspect, around 8200').  Overall though, minimal wet avalanche activity observed with this significant warm up..." Photo: B. Fredlund

Point releases across highway from Bacon Rind. 3/6/2020.

Photo: GNFAC

Point releases across the highway from Bacon Rind. 3/6/2020

Photo: GNFAC

Wet slide in Buffalo Horn Creek. 3/6/2020.

Photo: A. Norlander

Overview of an avalanche triggered on 2/27/2020 at 8:30 p.m. by a groomer between Storm Castle and Swan Creeks in the northern Gallatin Range. The driver was ok, but the machine did a full barrel roll and was very badly damaged. Photo: GNFAC

An avalanche triggered on 2/27/2020 at 8:30 p.m. by a groomer between Storm Castle and Swan Creeks in the northern Gallatin Range. The driver was ok, but the machine did a full barrel roll and was very badly damaged. The debris piled 8' deep on the road, which creates a terrain trap. Photo: GNFAC

An avalanche was triggered on 2/27/2020 at 8:30 p.m. by a groomer between Storm Castle and Swan Creeks in the northern Gallatin Range. The driver was ok, but the machine did a full barrel roll and was very badly damaged. Photo: GNFAC

From obs form: "While approaching Black Mountain from Pine Creek Lake.... We skied South aspect and as it warmed we triggered D1 R1 slabs that ran slow and short." Photo: T. Hoefler

From email: "Photo attached of a natural avalanche from yesterday, just south of Cooke City.  It's on an E, NE aspect, with a crown around 9,300'.  Looks like it occurred yesterday am, as a result of a cornice fall." B. Fredlund

Small natural wind slabs on Crown Butte. Broke overnight, observed morning of 2/25/2020.

Photo: GNFAC

Snowmobile triggered wind slab near Goose Lake. Triggered morning of 2/25/2020. Broke 1-2' deep on a small slope.

Photo: GNFAC

From obs: "Seemed stability was getting better, but did see this minor slide that pulled out on Scotch Bonnet Mountain. Evidently triggered by a snowmobile sometime mid-day Saturday (2/22)." Photo: R. Larson

"Avalanche debris we encountered while skinning up the access road. It piled roughly 15-20 feet onto the road." Photo: T. Papritz

"Very large and destructive deep slab just north of emigrant peak on a east-facing aspect. The debris likely ran over 1000 vertical feet and stopped towards the bottom right of the image. We think the smaller slide on the far right was triggered as a secondary slide as a result." Photo: T. Papritz

"Very large and destructive deep slab just north of emigrant peak on a east-facing aspect. The debris likely ran over 1000 vertical feet and stopped towards the bottom right of the image. We think the smaller slide on the far right was triggered as a secondary slide as a result." Photo: T. Papritz

From IG #gnfacobs post: "An avalanche from early Tuesday (02/18) morning caused by a natural cornice fall. Note the step down partway down the path. ENE @ 9700. Ran 1300’." Photo: A. Whitmore