Regional Conditions for Southern Madison

Today we rode into the Taylor Fork and Lionhead areas to remove our weather stations for the season. Photo: GNFAC

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

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

From obs: "On Thursday my group skied a few lines off the Lee side of skyline. Generally, all stability observations but one were good except for 1. We were skinning cross slope along the top of the apron toward the bottom of a couloir on the north aspect of White Peak to recon the couloir for possible ascent and skiing. As we approached the opening of the couloir, a large collapse occurred on a firm wind slab and a crack shot out across the bottom of the couloir an unknown distance. (We deemed it unwise to further investigate given the slope angle was nearly 40 degrees. It was quite puzzling the slope did not slide upon collapse and we were not about to further poke that bear.)

Photo: Z. Ferry

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

From an email, "It did look like the east face of Ramshorn Peak slid pretty recently. The blowing snow and clouds weren't conducive to good pictures but you can see the crown line below and to the right of the summit. Looked like a cornice fall triggered it." Photo: B. Richards

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

Looking up the path 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

Looking down the path 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

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

Skiers saw this 2-4' deep natural crown on Sunday 2/23/20. Photo: from IG @skishot

"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

"I had been riding trees most of the day down low and moved up to about mile marker 10 later in the day. Did a side hill through open trees and stopped on top of this slope. Watched it all propagate and slide below me." Photo: anonymous

Debris pile from the slide in Taylor’s Fork, crown of about 5-6’ and about 100' wide. Human triggered. Photo: Matt Seifert

Slide in Taylor’s Fork, crown of about 5-6’ and about 100' wide. Human triggered. Photo: Matt Seifert

Surface Hoar in Taylor Fork on 2/13/2020.

"...were up in Tepee today, we saw a couple small slides the one below look to be caused from a snowmobiler and we saw one other one high on the Whites peak ridge that looked to be a natural slide or maybe caused from a piece of cornise that broke off.  The rest of the ridge along White Peak also looked to be loaded up." Photo: J. Norlander

On 2/9/20 we saw deep avalanche crowns throughout the Bridger Range. These broke at various times throughout the recent storm that deposited 4 feet of snow with over 4" of SWE in the last week. This photo shows crowns from avalanches that broke across the entire drainage of Truman Gulch. Photo: GNFAC

On 2/9/20 we saw deep avalanche crowns throughout the Bridger Range. These broke at various times throughout the recent storm that deposited 4 feet of snow with over 4" of SWE in the last week. This photo shows debris from avalanches that broke across the entire drainage of Truman Gulch. Photo: GNFAC

We saw a group of six snowmobilers who said they triggered these slides in McAtee Basin on the left side of the meadow on Saturday, Feb 8. I didn't see tracks up on the hill or sidehill tracks so they may have triggered the slope from the flats below. The debris runs all the way to bottom of the hill. Photo: K Peaslee

We saw a group of six snowmobilers who said they triggered these slides in McAtee Basin on the left side of the meadow on Saturday, Feb 8. I didn't see tracks up on the hill or sidehill tracks so they may have triggered the slope from the flats below. The debris runs all the way to bottom of the hill. Photo: K Peaslee

We saw a group of six snowmobilers who said they triggered these slides in McAtee Basin on the left side of the meadow on Saturday, Feb 8. I didn't see tracks up on the hill or sidehill tracks so they may have triggered the slope from the flats below. The debris runs all the way to bottom of the hill. Photo: K Peaslee

"Noted two SS-D1.5/2 naturals (presuming based on lack of any sort of tracks) on Wheeler, typical spots for these conditions, both SE aspect around 8000'." Photo: G. Antoniolli

"Noted several avalanches (NW aspect ~ 8800') off of Elephant that traveled quite far into the trees where the summer trail typically runs, all appear to be new snow, D1- D2 in size, average 2' crowns, running on old/new interface from  Feb 2. They appear to have run midstorm, sometime yesterday (photos 1,2,3).  Above 9000', W Winds were crafting fresh wind slabs that were most reactive on a midstorm crystal/density change that buried a layer of stellars ~ 1' deep in shallower spots,  topped with denser snow." Photo: G. Antoniolli