Regional Conditions for Lionhead Range

The Lionhead area near West Yellowstone has the shallowest and weakest snowpack in our forecast region. The bottom half of the pack consists of weak, sugary facets. This well developed weak layer produced unstable results in stability tests on any slope that had wind drifted snow. With more snow and wind in the forecast, this area will experience increasingly unstable conditions. Photo GNFAC  

Yesterday at Lionhead Ridge near West Yellowstone we found a shallow and weak snowpack. A foot of weak, sugary snow on the ground will create unstable conditions where it is buried by thick drifts of snow, and when the area gets more snow later this week. Photo: GNFAC

Snow water equivalent at SNOTEL stations in the GNFAC advisory areas for the 18-19 season to date. Weak layers formed on the surface of the snowpack during the dry weather (flat section of lines), then they were buried by the recent 10-14" of snow (steep increase at end of graph). Image: GNFAC

From an email:

"By and large right side up snowpack. Some small facets below the 11/1 ice crust at the ground, but well bonded snowpack overall. Pit observations consistent with hand pits dug throughout the day touring north out of Bridger Bowl." Photo: M. Zia

From an email: "ECTP 5 at the top of a chute on the south face of the Texas Meadows knob. Propagated on a layer 15cm from the top of the snowpack." Photo: J. Zimmerer

From Instagram:

"Careful out there this year! While we are lucky enough to have a mostly stable snowpack here in Southwest Montana, we did just find this little wind slab well below the ridge line in Middle Basin. Slowboarder was fine" @chartierk

A skier found 80 cm of stable snow on an east facing slope at 9200' in Beehive Basin. Winds created these newborn cornices along the ridge. Photo: T. Allen

From e-mail: "Was descending off of Zach Attack tonight and set off a small slab in the gully on the decent. This was about 100 meters below the start of pitch 1. Constant whipping winds and lots of new deposited snow likely caused the slab to form. Climber caused. Didn’t carry me as it was small. Would be wary of the mummy cooler gullies abover scepter as well."

From e-mail: "Was descending off of Zach Attack tonight and set off a small lab in the gully on the decent. This was about 100 meters below the start of pitch 1. Constant whipping winds and lots of new deposited snow likely caused the slab to form. Climber caused. Didn’t carry me as it was small. Would be wary of the mummy cooler gullies abover scepter as well."

From a tour up Miller Creek: "Good stability and structure found overall.  No collapsing nor cracking experienced, minor wind effect, and only some minor point release avalanche activity noted on the east aspect of Crown Butte." Photo: B. Fredlund

Natural wind slab that broke after 3-4 feet of new snow over 6 days. Photo: B. VandenBos

Natural avalanche activity was widespread in Hyalite on Tuesday 11/6. Obs from e-mail: "The newest snow (about 18", I'd guess past 48hrs) is touchy soft slab. The top 8 inches also exhibit a storm slab-like quality.  There appears to be a very slight density change between the two.  Top 8" fracture and propagate cracks readily on gentle terrain, whereas in steeper terrain, the deeper slab (again, about 18" down) was propagating as I was skinning up the headwall in the steep creek drainages and steeper features nearby. Lots of natural activity on steeper terrain, but vis was limited. Photo: G. Antonioli

Natural avalanche activity was widespread in Hyalite on Tuesday 11/6. Obs from e-mail: "The newest snow (about 18", I'd guess past 48hrs) is touchy soft slab. The top 8 inches also exhibit a storm slab-like quality.  There appears to be a very slight density change between the two.  Top 8" fracture and propagate cracks readily on gentle terrain, whereas in steeper terrain, the deeper slab (again, about 18" down) was propagating as I was skinning up the headwall in the steep creek drainages and steeper features nearby. Lots of natural activity on steeper terrain, but vis was limited. Photo: G. Antonioli

From the MSU Backcountry Club Instagram page:

Warning! This is a current, fresh, crown in the northern Bridgers! Every aspect had a visible crown and avi debris! This crown was 56cm at it deepest and over 8 meters long. ECTP21@53 and CT24@54 on the overlying slab. Photo: @msubackcountryclub More Details.

This avalanche was observed on the morning of Friday 11/2. It broke from a natural trigger in the Big Couloir at Big Sky Resort. New snow fell and was drifted into slabs overlying older, hard layers of snow from October. The resort is not open and no people were in the area of the avalanche at that time. Photo: Big Sky Resort More details

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Wet slab avalanche in the Centennial range. Multiple days without freezing created widespread wet slides last week (5/6-5/11). Photo: @waxeman

Wet slab avalanche in the Centennial range. Multiple days without freezing created widespread wet slides last week (5/6-5/11). Photo: @waxeman

Wet slab avalanche in the Centennial range. Multiple days without freezing created widespread wet slides last week (5/6-5/11). Photo: @waxeman

Wet slab avalanche in the Centennial range. Multiple days without freezing created widespread wet slides last week (5/6-5/11). Photo: @waxeman

Wet slide carnage observed off of Skyline Ridge near Cabin Creek May 11/12. Many days of above freezing temperatures created widespread wet slide activity over the previous week. Photo: B. Lukens

Wet slide carnage observed off of Skyline Ridge near Cabin Creek May 11/12. Many days of above freezing temperatures created widespread wet slide activity over the previous week. Photo: B. Lukens

Massive cornices create a few hazards as they warm and weaken under the spring heat. They become easier to trigger, can break naturally, and form dangerous, deep cracks along ridgelines. From e-mail: "The crack was up to 30' deep, and had pulled large pieces of vegetation from the ridgeline it used to be attached to." Photo: S. Reinsel

From e-mail: "Photo of a couple of recent wet slab avalanches, just north of Silver Gate (on Mineral Mtn.). On a south aspect, around 9100'. The one on looker's left ran on April 23rd I think, and the one on looker's right April 27 or 28th. That's all the slab avalanches I've observed with these warm temps. Not a ton of wet loose activity to be seen either. Snowpack is holding in there!" Photo: B. Fredlund

Natural wet loose avalanches that slid during multiple days of well above freezing temperatures. Wet loose slides like this can run long distances and carry a lot of force. Multiple days with high temperatures of 50-60 F and overnight lows in the mid-30s to 40 F created a wet snowpack and wet slab and wet loose avalanches slid naturally. Photo: GNFAC

This small wet slab avalanches slid during multiple days of well above freezing temperatures. Though small, it is large enough to bury a person and would carry a lot of force. Multiple days with high temperatures of 50-60 F and overnight lows in the mid-30s to 40 F created a wet snowpack, and wet slab and wet loose avalanches slid naturally. Photo: GNFAC

Natural wet slab avalanche that ran during multiple days of well above freezing temperatures (4/26-4/28). Multiple days with high temperatures of 50-60 F and overnight lows in the mid-30s to 40 F created a wet snowpack and wet slab and wet loose avalanches slid naturally. Photo: GNFAC

Wet avalanches ran naturally last week during above freezing temperatures and sunshine after the last storm. Slides like this will be possible when the snowpack softens in the afternoon and will become more likely if the snowpack doesn't freeze overnight. Wet slides can run long distance and carry a lot of force. Photo: B. VandenBos

Recent snowfall followed by spring sunshine and above freezing temperatures created natural wet slab and wet loose activity. More slides like this are possible if temperatures do not freeze overnight, during heavy rain, or after the next snowfall. Photo: B. VandenBos

Cornices are massive and will break naturally with above freezing temperatures and hot, spring sun. Photo: B. VandenBos

Cornices are massive through the advisory area and will break naturally with above freezing temperatures and hot, spring sun. Photo: B. VandenBos

Cornices are a significant hazard this time of year. As temps warm above freezing, these overhanging masses of snow will become increasingly unstable. They can break farther back than you might expect and trigger large avalanches on the slopes below. They can fail naturally or with human triggers. 

This slide was triggered by the first skier of day off Saddle Peak. The skier was caught and carried 1,500 vertical feet. He was buried with his hand sticking out of snow. Unfortunately, he did not have a partner and was buried for over an hour. He did not survive. Photo: R. Gregoire   

This slide on Saddle Peak resulted in a fatality. It was triggered by a solo skier who was caught and buried. The slope was heavily wind loaded and the slide failed on a thin ice crust. Photo: R. Gregoire

Wet loose avalanches will be a growing concern as spring progresses. Sunshine, above freezing temps and rain can all produce dangerous wet snow avalanches. Watch for signs of instability such as roller balls, small point releases and wet snow above your boot top. Avoid being on or underneath steep slopes if signs on instability are observed. Photo: BBSP 

The crown ranged from 1-3' deep and was 75-100' wide. The avalanche was new, windblown snow on top of a thin ice crust. Aspect is east, slope angle is 37 degrees, and elevation is 9019'. Photo: GNFAC

Looking down the path with the burial location marked. Photo GNFAC