Regional Conditions for Southern Madison

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Debris from an older wet loose slide observed 4/20/19. Estimated to be a week old. Photo: G. Antonioli

Observed 4/20/19. Crown estimated 3-5' deep. Above freezing temperatures, sunshine and rain created a wet and weak snowpack. Photo: G. Antonioli

Observed 4/20/19. Crown estimated 3-5' deep. Above freezing temperatures, sunshine and rain created a wet and weak snowpack. Photo: G. Antonioli

From e-mail on 4/11/19: "We found reactive storm slabs and touchy windslabs near ridgelines. We kicked off a small windslab in 4th of July from the top of the couloir. Attached is a photo of the crown to give you a depth perspective. It was about 6 feet across and 3-4 inches deep."

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

A snowbiker was partially buried in a slide on the west side of Sage Peak in the southern Madison Range. The slide occurred on a southwest facing slope at 8,700 ft. and failed on weak snow near the ground. The wet slab avalanche was triggered as the biker was side-hilling across the slope. He was caught, carried and buried to his chest, but fortunately escaped unharmed. Photo: D. Talbert 

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.

A snowmobiler saw this recent activity on Saturday 3/9/19 on Cedar Mountain near Big Sky.

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

This slide on the NE face of Blackmore was triggered by the second skier. It was 8-12" deep and 100' wide and likely failed on small faceted crystals underneath the new snow. No one was caught. Going one at a time was good travel behavior that can save our lives when things go wrong.

Two avalanche on the south face of Cone Mountain, southern Madison Range. Observed on March 4th, 2019, likely occurred several days earlier. Photo: B. Elkin.

An avalanche on an east/northeast aspect of White Peak in Upper Tepee Basin, southern Madison Range. Observed on March 4th, 2019, likely occurred several days earlier. Photo: B. Elkin.

Riders saw this avalanche (center of photo) on Saturday (3/2) just east of Sage Peak. Photo: P. Honsinger

A snowmobiler sent in this photo of multiple natural avalanches near Woodward Mtn. He also reported large avalanches near Pika Point and Skyline Ridge that failed at the ground. Photo: P. Honsinger

A snowmobiler triggered this slide on the afternoon of 3/2/19 behind Sage Peak in the southern Madison Range. Photo: J. Hillier

A snowmobiler triggered this slide on the afternoon of 3/2/19 behind Sage Peak in the southern Madison Range. Photo: J. Hillier

We received this report of an unusually large natural avalanche in the East Mill Creek drainage: " First time in 17 years we have had an avalanche come into our road. Natural, maybe from a point release that fractured new snow about 20 inches at the crown, propagated 50 yards, ran about 300 feet without stepping down, leaving about 5 foot deep debris. A new 2 inches is covering the debris that likely went during this afternoons warming."  Photo and comments: L. Watson

This avalanche failed on the ground up on Buck Ridge near the First Yellowmule. It was human-triggered, but nobody was caught or buried. Photo: N. James

This avalanche failed on the ground up on Buck Ridge near the First Yellowmule. It was human-triggered, but nobody was caught or buried. Photo: N. James

Snowmobile - triggered avalanche in the McAtee Basin area near Buck Ridge. The avalanche was triggered unintentionally from the runout zone and propagated all the way up to the ridge above the riders. Luckily, nobody was caught or buried. Photo: J. Stoner

Snowmobile - triggered avalanche in the McAtee Basin area near Buck Ridge. The avalanche was triggered unintentionally from the runout zone and propagated all the way up to the ridge above the riders. Luckily, nobody was caught or buried. Photo: J. Stoner

This avalanche occurred in the trees on Ernie Miller ridge. Photo: F. Madsen

Large avalanche that failed deep in the snowpack at Ernie Miller. This is the second photo we've recieved of this bowl sliding this season (last one was on Dec. 15th). Photo: F. Madsen

This slide appeared to be triggered by a falling cornice. It broke near the ground and propagated two hundred feet wide. It snapped trees and left a debris pile up to ten feet deep. This avalanche illustrates that large and dangerous avalanches remain possible in the southern Madison Range and mountains near West Yellowstone. Photo: GNFAC 

This small slide was triggered by a snowmobiler in the southern Madison Range. Although small, this slide is bull's eye information that larger slides are possible on similar slopes. Photo: GNFAC  

Cornices are growing large after a series of storms in the southern Mountains. These cornices make up the rim of Sunlight Basin in the southern Madison Range. Cornices are good indicators of which slopes are wind loaded. It's often best to avoid riding on or underneath slopes attached to large cornices. Photo: GNFAC

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."

A skier headed up Bacon Rind to Ernie Miller Ridge and saw this avalanche in the distance. He reported it, "35 degree wind loaded NE slope at 9,600. It appeared to be about 1 - 1.5 m deep and 100 ft across." Photo: W. Casper

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

We triggered this avalanche remotely from about 50 feet above the crown up on the ridge. The crown was 1-2' deep, 100' wide, and ran between 200 and 300 vertical feet through trees and cliffs. Another slide failed sympathetically at the same time, 100' down the ridgeline. The slides failed on a 40 cm thick layer of depth hoar, which composed half of the snowpack. Photo: GNFAC

We triggered this avalanche remotely from about 50 feet above the crown up on the ridge. The crown was 1-2' deep, 100' wide, and ran between 200 and 300 vertical feet through trees and cliffs. Another slide failed sympathetically at the same time, 100' down the ridgeline. The slides failed on a 40 cm thick layer of depth hoar, which composed half of the snowpack. Photo: GNFAC

We triggered this avalanche remotely from about 50 feet above the crown up on the ridge. The crown was 1-2' deep, 100' wide, and ran between 200 and 300 vertical feet through trees and cliffs. Another slide failed sympathetically at the same time, 100' down the ridgeline. The slides failed on a 40 cm thick layer of depth hoar, which composed half of the snowpack. Photo: GNFAC

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