This wet loose avalanche is a great example of where they often occur. Rocks absorb extra heat from the sun and can quickly melt and destabilize the snow. Either move under areas like this early in the morning (as we did), or if you have to travel under them later in the day, move quickly.
Trip Planning for Lionhead Range
Primary Problem: Loose Wet
Bottom Line: Today and this weekend, the main threat is wet snow avalanches. A minimal refreeze of the snow this week combined with very warm weather the next few days will increase the odds of wet loose avalanches. Past 5 Days
Sun Apr 20
Low
Low
Mon Apr 21
None
None
Fri Apr 25
None
None
Mon Apr 28
None
None
Fri May 2
None
None
Relevant Photos
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Understanding Avalanche Safety Preparedness – 5-Minute Survey for Motorized Users
We need your input! Eastern Oregon University is conducting a survey to better understand avalanche safety preparedness among motorized backcountry users like you. Your feedback will help us learn more about who is purchasing and practicing with avalanche rescue gear (beacon, probe, shovel) and participating in avalanche education—and why some riders aren’t. The survey is confidential and anonymous.
Your feedback is invaluable in improving avalanche education and awareness. Please take a moment to share your experience and help us make a difference.
https://eoustmhs.qualtrics.com/jfe/form/SV_3L8QKAuZzcxJBLo
Thank you for your time and for being a part of this important effort!
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Large chunks of debris from a natural avalanche in Targhee Creek. Photo: GNFAC
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We saw many crowns of wind slab avalanches along Lionhead Ridge. Photo: GNFAC
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Cornice collapse and small avalanche at the start of Lionhead Ridge. Photo: GNFAC
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Mar 9. We rode out Lionhead Ridge... there were two or three shallow small wind slabs below Lionhead Ridge. Photo: GNFAC
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Mar 9. We rode out Lionhead Ridge... there were two or three shallow small wind slabs below Lionhead Ridge. Photo: GNFAC
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From obs: "Looks like a recent naturally triggered slide towards the Idaho wilderness boundary on lionhead."
Photo: M. Klahr
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Airplane bowl this afternoon after a rider triggered slide. There is a down track in the middle of the crown face
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Airplane bowl this morning, no avalanche
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A rider triggered a huge avalanche in the uppermost reaches of Targhee creek on a north facing slope at 9200'
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A rider triggered a huge avalanche in the uppermost reaches of Targhee creek on a north facing slope at 9200'
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A rider triggered a huge avalanche in the uppermost reaches of Targhee creek on a north facing slope at 9200'
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At Lionhead a weak layer generally 2-3 feet deep is obvious in this snowpit wall.
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Remotely triggered the avalanche from 150 feet away. It broke 200' wide and 1-3 feet deep. It ran an estimated 200' vertical feet
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Remotely triggered the avalanche from 150 feet away. It broke 200' wide and 1-3 feet deep. It ran an estimated 200' vertical feet
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From FB message: "Small slide in lower elevation back by lionshead"
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From obs: "We saw this today after it happened. Looked like a snowmobile triggered it. I believe it is mostly south facing." Photo: D. Haluptzok
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We saw two recent shallow wind slab avalanches. No recent slides breaking deeper.
This one at NE 9000' -
Plenty of wind slabs ranging in size on Lionhead ridge and on surrounding slopes. Photo: Riley
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Plenty of wind slabs ranging in size on Lionhead ridge and on surrounding slopes. Photo: Riley
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Plenty of wind slabs ranging in size on Lionhead ridge and on surrounding slopes. Photo: Riley
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1 meter deep snowpack showing the obvious facets in the bottom third
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We dug a pit on an East facing aspect below the slope we had planned to ride. The height of snow was about 110 cm and there was a very concerning layer of large facets at 75cm deep going to the ground. Photo: C Culver
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Our results were CT17 SPQ2 and ECTP26 SCQ1. Bother failures during tests were on the layer of facets and on the CT and ECT our columns easily separated from the facet layer after failure. Photo: C Culver
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On Jan 12, we saw 4-5 avalanche crowns that were up to a week old, some had been reported and a few we had not heard of. Two were ~2' deep on less wind affected slopes lower down in the trees, but probably had some previous wind-loading. Photo: GNFAC
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On Jan 12, we saw 4-5 avalanche crowns that were up to a week old, some had been reported and a few we had not heard of. Two were ~2' deep on less wind affected slopes lower down in the trees, but probably had some previous wind-loading. Photo: GNFAC
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On Jan 12 We saw 4-5 avalanche crowns that were up to a week old, some had been reported and a few we had not heard of. The pictured one was a 3-4'+thick slab on a rocky heavily wind-loaded slope off Lionhead ridge. Photo: GNFAC
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From IG Jan4, Photo: J. Urell
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From IG Message Jan 4."They happened today because I did not see the debris on way in". Photo: T. Urell
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Remote triggered this avalanche at Lionhead. We were snowmobiling to the left of where the avalanche occurred. No one was caught.
Coordinates: 44°43'36.8"N 111°19'05.0"W
Photo: Ben
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Settling and collapsing on E-NE slopes above Hebgen. Full slope collapses and cracks, approximately 28 degree slope pictured.
Photo: C Koch
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While touring up a low-angle ridge in the northern Lionhead, I experienced several large collapses, notably one that triggered a cornice fall from 50’ away. Another remote collapse caused about 500’ of an E facing bowl to propagate, but not slide. ~9200’ E-SE
Photo: N Sramek
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While touring up a low-angle ridge in the northern Lionhead, I experienced several large collapses, notably one that triggered a cornice fall from 50’ away. Another remote collapse caused about 500’ of an E facing bowl to propagate, but not slide. ~9200’ E-SE
Photo: N Sramek
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There was a natural avalanche on the landslide face above quake lake. The avalanche failed on a weak layers near the ground and broke several hundred feet wide.
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From obs on 12/29: "On our way out near the cabin I cut a line close to a creek to see if I could trigger something."
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From obs on 12/29: "On our way out near the cabin I cut a line close to a creek to see if I could trigger something."
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Occurred during the day on 12/28 Photo: GNFAC
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Videos- Lionhead Range
Weather Stations- Lionhead Range
Weather Forecast Lionhead Range
Extended Forecast for10 Miles WNW West Yellowstone MT
Today
High: 57 °F
Mostly Sunny
then Chance
ShowersTonight
Low: 34 °F
Showers
LikelyMonday
High: 37 °F
Chance
Rain/Snow
then Snow
Likely and
BreezyMonday Night
Low: 26 °F
Chance Snow
and BlusteryTuesday
High: 43 °F
Slight Chance
SnowTuesday Night
Low: 28 °F
Mostly Clear
Wednesday
High: 51 °F
Sunny
Wednesday Night
Low: 34 °F
Mostly Clear
Thursday
High: 55 °F
Sunny then
Chance
Showers
The Last Word
Thank you for another successful season. Our success is directly related to support from our community and the Forest Service. Thanks to the readers of the forecast, everyone that sent in observations, took an avalanche class, or donated money, time or gear. We will issue conditions updates on Mondays and Fridays through April.
GENERAL SPRING SNOWPACK AND TRAVEL ADVICE
Spring weather can be highly variable and create a mix of avalanche problems. Snow conditions and stability can change drastically from day to day or hour to hour. Anticipate rapid change and plan accordingly. Abundant snowfall over the winter with more spring snow to come makes avalanches possible into summer.
NEW SNOW AND WIND LOADED SLOPES
Spring storms are notorious for depositing heavy amounts of snow in the mountains. Even with a deep and generally stable snowpack throughout the advisory area, heavy and rapid loads of new snow will decrease stability. The main problems to look out for are avalanches breaking within the new snow, wind slabs, and loose snow avalanches. The likelihood of triggering an avalanche spikes during and immediately after snowstorms. New snow instabilities tend to stabilize quickly, but it’s a good idea to give fresh snow a day to adjust before hitting big terrain. New snow instabilities can be challenging to assess, and spring storms bond to old snow differently across aspects and elevations. Conservative terrain selection is essential during and immediately following storms. Avoid wind-loaded slopes and slopes steeper than 35 degrees for 24-48 hours after new snow and wind.
New snow can quickly change from dry to wet on a spring day, and stability can decrease rapidly with above freezing temperatures or brief sunshine. New snow may bond well early in the morning and then easily slide later. Wet loose slides are likely during the first above freezing temperatures or sunshine immediately after a storm. Anticipate changes in snow stability as you change aspect or elevation and over the course of the day. An early start is always an advantage. Be ready to change plans or move to safer terrain at the first signs of decreasing stability.
WET SNOW AVALANCHES
Spring and wet snow avalanches go hand-in-hand. Above freezing temperatures, rain, and/or intense sunshine cause the snow to become wet and weak and make wet avalanches easy to trigger or release naturally. Conditions tend to become most unstable when temperatures stay above freezing for multiple days and nights in a row. Avoid steep terrain, and be aware of the potential for natural wet avalanches in steep terrain above you, if you see:
- Heavy rain,
- Above freezing temperatures for more than 24 hours,
- Natural wet avalanches,
- Rollerballs or pinwheels indicating a moist or wet snow surface,
- Or if you sink to your boot top in wet snow.
In general, if the snow surface freezes solid overnight, the snowpack will be stable in the morning and stability will decrease through the day as snow warms up. The snow surface hardness, rate of warming, duration of sunshine, aspect and elevation determine how fast stability will decrease through the day. Be aware that sunny aspects may have a wet snow avalanche danger while shadier slopes still have a dry snow avalanche danger. Getting off of steep slopes should be considered when, or before, the above signs of instability are present. Wet snow avalanches, whether loose snow or slabs, can be powerful, destructive and very dangerous. Conservative terrain choices, starting early in the day, and careful observations can keep you safe.
CORNICES
Cornices along ridgelines are massive and can break under the weight of a person (photo). Prolonged above freezing temperatures and rain make them weaker and possible to break naturally. They can break off suddenly and farther back than one might expect. Cornice falls can also entrain large amounts of loose snow or trigger slab avalanches. Stay far back from the edge of ridgelines and minimize exposure to slopes directly below cornices. Regardless of whether a cornice triggers a slide or not, a falling cornice is dangerous to anyone in its path.
DISCLAIMER
It does not matter if new snow falls or not, avalanches will continue to occur until the existing snowpack is mostly gone. Always assess the slope you plan to ride with diligence and safety in mind. Do not let your guard down. Travel with a partner, carry rescue gear and only expose one person at a time in avalanche terrain.
Have a safe and enjoyable spring and summer!
Mark, Alex, Ian and Dave
For more spring travel advice see this article from our GNFAC forecaster blog.