23-24

Multiple slides on buck

Date
Activity
Snowboarding
Snowmobiling

Saw multiple large slides around the McAtte drainage N/NE aspects. Some were larger than others but all ran on what looked like a persistent grain or even to the ground in some. Probably natural released over last few days.

During our time out the wind was hammering the ridge and clearing transporting and forming slabs. 

Region
Northern Madison
Location (from list)
Buck Ridge

Variable in Hyalite

Date
Activity
Skiing

We noticed that a widespread crust had formed at lower elevations from the recent warm spell, especially in areas without consistent shade. The snow that remained available for transport was easily being picked up by moderate to strong SW winds at treeline. Many tracks had been filled in by the wind transported snow, and a dense, hollow windslab was found in isolated spots.

Region
Northern Gallatin
Location (from list)
Lick Creek
Observer Name
Wyatt Hubbard

Large slide north east basin of Fan Mountain

Fan Mountain
Northern Madison
Code
N-R3-D3-O
Aspect
NE
Latitude
45.29810
Longitude
-111.52400
Notes

This avalanche likely happened in the last 24 hours following a large increase in windspeed beginning early in the morning on 02/24/2024. 

From obs: "Large slide in the north basin of Fan Mountain. The flies is below the north, northeast couloir and the crown runs all the way around the basin. It went to the ground below the couloir and a few other places. 10ft crown probably at the biggest point below the couloir. "
 

 

Number of slides
1
Number caught
0
Number buried
0
Trigger
Natural trigger
R size
3
D size
3
Bed Surface
O - Old snow
Problem Type
Persistent Weak Layer
Slab Thickness
72.0 inches
Snow Observation Source
Large slide north east basin of Fan
Slab Thickness units
inches
Single / Multiple / Red Flag
Single Avalanche
Advisory Year
23-24

From obs: "Several small slabs pulled out above The Shimmy, left of Cleo's. Observed from across the valley while climbing the Dribbles. Did not observe them run, only saw the crowns. Unknown date of avalanches, but crowns were quite distinct from across the way." Photo: M. Zia

Avalanche Details: Avalanche Above Twin Falls
Forecast link: GNFAC Avalanche Forecast for Mon Feb 26, 2024
Northern Gallatin, 2024-02-24
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    • Avalanches above Cleos

    Date
    Activity
    Ice Climbing

    Several small slabs pulled out above The Shimmy, left of Cleo's. Observed from across the valley while climbing the Dribbles. Did not observe them run, only saw the crowns. Unknown date of avalanches, but crowns were quite distinct from across the way.

    Lots of wind transport all day.

    Region
    Northern Gallatin
    Location (from list)
    Hyalite - main fork
    Observer Name
    Matt Zia

    Wind drifting snow and recent avalanches

    Date
    Activity
    Snowmobiling

    We rode to the south shoulder of Scotch Bonnet, then over Lulu Pass, towards Round Lake behind the north end of Sheep Mtn., and back to Lulu Pass. It was snowing very lightly and wind was blowing strong. Wind was blowing snow into drifts 6-8" thick on the leeward side of trees and convexities. We had intermittent ok visibility and could see old debris from last weekend on east Henderson, and we got a pretty good look at the slides on Fisher Mtn. that were triggered yesterday. They appeared 2-3 feet deep, and the debris was very hard. Crowns were already at least half drifted in.

    We saw another slide on the north end of Sheep Mtn. on a slope above the steep chute where people climb out of Goose Creek (photos attached). This slide had not been reported previously and looked similar in age to the two triggered yesterday, so maybe broke naturally or human-triggered in last 24 hours. It broke near a scoured north facing ridgeline, 1-1.5' deep, 175' wide. HS-R3-D2-O.

    We dug a pit on the south facing shoulder of Scotch Bonnet and had an ECTP24, down 1.5 feet, not on the previous layers of concern which were lower down (pit attached).

    Regardless of stability test results or which layer slides are breaking on, recent avalanche activity and more wind-loading is enough evidence to avoid avalanche terrain.

    Region
    Cooke City
    Location (from list)
    Scotch Bonnet
    Observer Name
    Alex Marienthal

    Large slide north east basin of Fan

    Date

    Large slide in the north basin of fan mountain. The flies is below the north, north east couloir and the crown runs all the way around the basin. It went to the ground below the couloir and a few other places. 10ft crown probably at the biggest point below the couloir. 
     

    no photos due to poor camera

    Region
    Northern Madison
    Location (from list)
    Fan Mountain

    GNFAC Avalanche Forecast for Sat Feb 24, 2024

    Snowpack and Avalanche Discussion

    <p><span><span><span><span><span><span>Yesterday near Cooke City a snowmobiler triggered a large avalanche, was caught and carried, but luckily not buried or injured. At the same time another avalanche released sympathetically on an adjacent slope (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/30998"><span><span><span><strong><span…;). Also yesterday, near Big Sky a pair of riders triggered two avalanches from flatter slopes nearby (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/30994"><span><span><span><strong><span… and details</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>). These avalanches show dangerous conditions exist. Today people can easily trigger large avalanches, potentially from flatter terrain below steep slopes.</span></span></span></span></span></span></p>

    <p><span><span><span><span><span><span>Over the last week 3-5” of snow fell near Big Sky, West Yellowstone, Island Park and Cooke City, and even this little amount of snow has prevented the unstable snowpack from gaining strength. Moderate to strong wind yesterday and today drifted snow into thicker slabs, keeping the snowpack especially unstable on wind-loaded slopes.&nbsp;</span></span></span></span></span></span></p>

    <p><span><span><span><span><span><span>This season’s snowpack is unique. Typically a snowpack becomes more stable over time with minimal snowfall or wind-loading. However, we have seen steady avalanche activity since early January, even during times without new snow or wind (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/weather/wx-avalanche-log"><span><span><span… and avalanche log</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>). Weak layers of facets and surface hoar buried 2-4 feet deep make up the foundation of the snowpack, and are as weak as we’ve seen. The snowpack needs to show proof it has changed before we can begin to trust it, and that has not happened. The best plan is to avoid riding on or beneath slopes steeper than 30 degrees. Avalanche danger is CONSIDERABLE.</span></span></span></span></span></span></p>

    <p><span><span><span><span><span><span>In the Bridger Range and Hyalite there has been less recent snow and avalanches, showing the likelihood of triggering an avalanche is slightly lower compared to the rest of our forecast area. However, the snowpack has weak, sugary snow trying to support overlying slabs, and it remains possible for a person to trigger a large avalanche. Avalanches last weekend in the Bridgers, near </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/30935"><span><span><span><strong><span… Peak</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span> and </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/30937"><span><span><span><strong><span… of Saddle Peak</span></span></u></span></strong></span></span></span></a>,&nbsp;<span><span><span><span><span><span>and on </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/30949"><span><span><span><strong><span…. Bole</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span> in Hyalite are examples of the avalanche potential.</span></span></span></span></span></span></p>

    <p><span><span><span><span><span><span>If you consider stepping into steeper terrain, start with smaller, simple slopes that don’t have recent wind loading and have good runouts below. Look for signs of instability and perform snowpack tests, and be ready to change plans if you see any red flags. Watch </span></span></span></span></span></span><a href="https://www.youtube.com/watch?v=vD42TrROj7k&amp;list=PLXu5151nmAvSH326z…’s video from the Throne</span></span></u></span></strong></span></span></span></a><span><span><span><strong><span><span> </span></span></strong></span></span></span><span><span><span><span><span><span>and </span></span></span></span></span></span><a href="https://www.youtube.com/watch?v=On68EbgLFbM&amp;list=PLXu5151nmAvSH326z…’s video from Hyalite</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span> for more travel and snowpack assessment tips during these conditions. Today, buried weak layers make large, human triggered avalanches possible, and the avalanche danger is MODERATE.</span></span></span></span></span></span></p>

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