Regional Conditions for Centennial Range

Natural wet slabs were widespread on Fan Mtn. near Big Sky during the week of 5/13-5/16. Photo: E. Mullen

Natural wet slabs were widespread on Fan Mtn. near Big Sky during the week of 5/13-5/16. Photo: E. Mullen

This natural wet slab slid early this week, Monday (5/13) or early Tuesday (5/14), near Beehive Peak. This photo was taken 0745 Tuesday morning. Photo: @cfirer

Debris from a wet slab that released naturally Tuesday evening on saddle Peak. Debris ran very far into the runout compared to similar sized dry slabs that often occur on this path. "South side of 1/4 Saddle slid sometime last night. Looks like cornice drop then step down to near ground. Hi yesterday at Alpine was 62." -R. Elliott/BBSP

This wet slab released naturally Tuesday evening on saddle Peak. "South side of 1/4 Saddle slid sometime last night. Looks like cornice drop then step down to near ground. Hi yesterday at Alpine was 62." -R. Elliott/BBSP

"South side of the Glide Plane released as a glide avalanche last evening (May 12th) sometime around 6 pm according to source. Bed surface was ground in starting zone of wet clay soil sparsely covered in long grass.  Debris chunks, some snowmobile sized, rode up on surface and slid approx. 200 vert.  Debris could have bumped a tower on the old Alpine lift if it still lived there. Last freeze was 6 am on the 10th of May.  The high temperature on the 12th was 59 degrees at 4 pm." Photo and observations: BBSP

"South side of the Glide Plane released as a glide avalanche last evening (May 12th) sometime around 6 pm according to source. Bed surface was ground in starting zone of wet clay soil sparsely covered in long grass.  Debris chunks, some snowmobile sized, rode up on surface and slid approx. 200 vert.  Debris could have bumped a tower on the old Alpine lift if it still lived there. Last freeze was 6 am on the 10th of May.  The high temperature on the 12th was 59 degrees at 4 pm." Photo and observartions: BBSP

Skiers found fresh wind slabs that were easily triggered on Saturday 4/27 near Beehive Basin in the northern Madison Range. Photo: E. Birkeland

Spring Sled Fest is May 18th! DJ, Free BBQ, Raffle. All proceeds go to the Friends of the Avalanche Center. More event details here: https://www.facebook.com/events/2290792671007553/ Thanks to Mark Christensen @markass406 and Nick Donovan @skidooin_it for organizing the event.

Skiers easily triggered loose snow avalanches of the 3-5” of new snow. This morning (4/27) on the Bridger Ridge. Photo: @smooneyski

Skiers easily triggered loose snow avalanches of the 3-5” of new snow. This morning (4/27) on the Bridger Ridge. Photo: @smooneyski

Link to donate to the Friends of GNFAC: https://www.givebiggv.org/organizations/friends-of-the-gallatin-national-forest-avalanche-center

Below 3-5" of new snow there is a supportable frozen crust on top of a wet snowpack on most slopes. Avalanches are mostly confined to the new snow on top of this crust (wet loose, dry loose, wind slabs). However, where the snowpack did not freeze below the new snow, or when this crust melts, deeper wet slides are possible. Photo: GNFAC

Snowmobile-triggered slide near Fairy Lake on Saturday (3/30). New snow was drifted into small wind slabs that may remain reactive in isolated areas.  Photo: P. Cronin

Outside Cooke City up Zimmer Creek, a skier spotted this cornice fall which triggered a small pocket down low. Photo: F. Madsen

Many wet loose and wet slab avalanches were seen near Zimmer Creek (north of Cooke City) on south and east aspects. Temperatures were warm at 10,000 feet. Photo: F. Madsen

This photo near Lionhead, is indicative of the wet loose avalanches we are seeing on many low elevation, south facing slopes throughout our advisory area. Daytime temperatures near 50F will make avalanches like this more frequent and widespread in the coming days.

Low angle metal roofs have heavy, thick slabs of snow that built up during persistent cold temperatures. These slabs will slide during warm temperatures. Be on the lookout for overhead hazard and be cautious where you walk or park your car during warm sunny days. An additional urban hazard are large icicles are that will break during warm days. Photo: A. Schauer

This slide was triggered on a steep (40 deg) southeast facing slope at Round Lake outside Cooke City. It failed 8" deep on a layer of graupel and small facets. An adjacent hill slid at the same depth beforehand. This layer is not on most slopes, but as this slide shows it is on some. Doug was in the area and dug a pit in the crown soon after it was triggered. Photo: J. Fritz

From e-mail: "Widespred slide activity from the last storm cycle, e.g. 2/14-2/18 ranging from E-NE to W. Aspects all elevations, creek bottoms slid at 7000' and peaks slide at 9800'. DEEP crownlines. From a dist. 4'-6', mostly in wind loaded terrain, micro-ridges, and corniced areas." Photo: S. Hansen

From e-mail: "Widespred slide activity from the last storm cycle, e.g. 2/14-2/18 ranging from E-NE to W. Aspects all elevations, creek bottoms slid at 7000' and peaks slide at 9800'. DEEP crownlines. From a dist. 4'-6', mostly in wind loaded terrain, micro-ridges, and corniced areas." Photo: S. Hansen

This snowmobile was fully buried, along with its rider on February 7th, 2019, in the Centennial Range.

Photo of the snowmobile triggered slide that fully buried a rider on February 7th, 2019.

A large snowmobile triggered avalanche in the Gravelly Range (Outside of advisory area) on February 10th, 2019.

From email: "One rider was involved in the incident and was fortunate to be on the upper left side of the bowl when he saw the slide start. ... the crown was about 325 wide and varied in depth from 1 to 4 or 5 feet.  The ridge line was wind loaded and this was an issue we had discussed as a group and wanted to avoid.  We had read the reports for the day and knew that wind loading as well as a persistent week layer were both concerns. .... The rider involved entered the area from around where the road switchbacked and did not realize what was above him due to reduced visibility."

This avalanche broke on weak snow in the lower 1/3 of the snowpack after a storm dropped 2-3' of heavy snow between 2/3 and 2/5/19. Photo: GNFAC

Multiple large avalanches occurred in the Lionhead area near West Yellowstone after 2-3’ of heavy snow earlier this week. Photo: GNFAC

This avalanche was triggered by snowmobilers on 2/6. 2-3’ of heavy snow earlier this week fell on a weak snowpack making large avalanches possible. Photo: GNFAC

This avalanche was triggered by snowmobilers on 2/6. 2-3’ of heavy snow earlier this week fell on a weak snowpack making large avalanches possible. Photo: GNFAC

From an email, "Observed this large avalanche while driving north from Jackson Hole today.  (on the E, NE aspect of Sawtell Peak, in the Centennial Mountains)"

Likely released in the last day or so with the Avalanche Warnings on Sun, Mon and Tuesday. Photo: B. Fredlund

Snowmobilers in the Lionhead area got unstable test results, easily propagating fractures in ECT tests on a weak layer buried about 50 cm deep. Photo: J. Norlander

This photo was taken by a FS snow ranger on Feb 1st. These avalanches likely occurred towards the end of a period of steady snowfall from Jan 16th to 28th. From e-mail: "The Reas Peak area had 7 slides that I could see from the bottom of the drainage, most of them looked to have occurred with the last storm and had a northerly influence to their aspect. The largest and most recent slide I included in the [above photo], Reas Peak is the highest peak on the left in the photo and the slide path is on a NE aspect. If you look close at the photo you can see a 2-3’ crown on the far left side of the frame on the north aspect of Reas from another slide." Photo: C. Hericks

This photo of an avalanche on the north side of Reas Peak was taken by a FS snow ranger on Friday, Feb 1. It likely occurred towards the end of a period of steady snowfall from January 16th to 28th. Photo: C. Hericks

Mount Jefferson (just north of Reas Peak) is the peak in the background. Nasty avalanche on persistent weak layer in the foreground. Photo: B. VandenBos

Large avalanche on Bald Peak in the Lionhead area near West Yellowstone. Photo: B. VandenBos

This was one of multiple avalanches triggered remotely from low-angle slopes connected to steep terrain in the Gravelly Range on Sunday. Photo: S. Olson

Crown of avalanche that was triggered by a group of four skiers. Two were partially buried (1 injured, 1 killed) on 1/25/19. They were all ascending and near the top of the path when the avalanche broke. The top two skiers held onto trees as the avalanche pushed by them. Photo: GNFAC

Overview of avalanche path where a group of four skiers were caught, and two were partially buried (1 injured, 1 killed) on 1/25/19. Crown is marked by black line and location of partial burial/deceased is tip of red arrow. The other partially buried skier was 200' lower. They were all ascending and near the top of the path when the avalanche broke. The top two skiers held onto trees as the avalanche pushed by them. Photo: GNFAC

From an email:

"...was riding with a group near the Two Top area and remotely triggered this slide as rode past this drainage on the top of the ridge. It was a north facing wind loaded slope in the 38 degree slope range. It broke about 12 inches deep and looked like it was from the last snow/wind loading." Photo: J. Norlander