24-25
Weak Layers and Mid/Low-Elevation Snow
Date
Activity
Skiing
Today, we traveled up the Deer Creek drainage north of Big Sky. We experienced no cracking or collapsing and saw no recent avalanches. We dug in the snow on a S aspect at 7680' with unremarkable results. We dug again on a NE aspect at 8200' and got an unstable test result (ECTP 28) on surface hoar and near-surface facets buried under a 2' slab (F - 1F+ hardness).
A few keys points from today:
- Mid to Low-elevation snow exists in many areas that typically do not hold rideable snow during the winter. These zones are typically much shallower and weaker. Avalanche terrain exists at mid to low-elevations too. Assume a shallow, weak snowpack in these areas and easily confirm by digging down to see what is going on underneath your feet.
- Persistent weak layers are still present and are reactive in snowpits. Surface hoar and near-surface facets exist around 2' deep in the snowpack. These layers do not exist on every slope and were stubborn in snowpit tests, but there is still a possibility of triggering an avalanche within this layer.
- Wind loaded terrain grows less sensitive by the day but is still where the likelihood of finding the most unstable snow is the highest.
There are a lot of abnormal, mid to lower-elevation zones out there holding great snow and riding conditions - just remember that there are still terrain and snowpack features to be on the lookout for and avoided. Step off the skin track, look out for signs of red flags and dig down to see what is going on beneath your feet before committing to ascending or descending steep slopes.
Region
Northern Madison
Location (from list)
NORTHERN MADISON RANGE
Observer Name
H. Darby
Wind Slab Avalanches near Zimmer Creek
Zimmer Creek
Cooke City
Code
SS-R1-D1
Latitude
45.09990
Longitude
-109.88400
Notes
Went skiing north of Cooke City today near Zimmer Creek. I saw a few wind slabs. Some appeared to be skier triggered, some were natural. No other avalanches seen. Moderate to strong wind from the west all day. I saw shooting cracks in obviously windloaded areas.
Number caught
0
Number buried
0
Avalanche Type
Soft slab avalanche
R size
1
D size
1
Problem Type
Wind-Drifted Snow
Snow Observation Source
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Multiple Avalanches
Advisory Year
Saw a few wind slabs. Some appeared to be skier triggered, some were natural. Photo: BPG
Avalanche Details: Wind Slab Avalanches near Zimmer Creek
Cooke City, 2025-02-10
Saw a few wind slabs. Some appeared to be skier triggered, some were natural. Photo: BPG
Avalanche Details: Wind Slab Avalanches near Zimmer Creek
Forecast link: GNFAC Avalanche Forecast for Tue Feb 11, 2025
Cooke City, 2025-02-10
Forecast link: GNFAC Avalanche Forecast for Tue Feb 11, 2025
Zimmer Creek Obs
Date
Activity
Snowboarding
Went skiing north of Cooke City today near Zimmer Creek. I saw a few wind slabs. Some appeared to be skier triggered, some were natural. No other avalanches seen. Moderate to strong wind from the west all day. I saw shooting cracks in obviously windloaded areas.
Region
Cooke City
Location (from list)
Zimmer Creek
Observer Name
Beartooth Powder Guides
GNFAC Avalanche Forecast for Mon Feb 10, 2025
Snowpack and Avalanche Discussion
<p><span><span><span><span><span><span>Human-triggered avalanches are likely on wind-loaded slopes today. Recent snow was drifted into thicker and stiffer slabs which have been easy to trigger, and will remain reactive for at least another day. </span></span></span></span></span></span></p>
<p><span><span><span><span><span><span>Yesterday we witnessed and received reports of natural and rider triggered </span></span></span></span></span></span><span><span><span><strong><span><span>wind slab avalanches</span></span></strong></span></span></span><span><span><span><span><span><span> breaking 1-2 feet deep and 20-200 feet wide (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/avalanche-activity"><span><span><span><span… activity list</span></span></u></span></span></span></span></span></a><span><span><span><span><span><span>). Notable avalanches among yesterday’s activity were a couple snowmobiler triggered slides in the southern Madison Range (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/34102"><span><span><span><span><span><…;), and natural and snowboarder triggered avalanches near Cooke City (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/34096"><span><span><span><span><span><…;, </span></span></strong></span></span></span><a href="https://www.youtube.com/watch?v=q3OxZUjHYfs"><span><span><span><span><s…;
<p><span><span><span><span><span><span>Today similar slides can be triggered and be large enough to bury or injure a person. Even smaller slides can easily knock you off your feet and be dangerous in terrain with trees, cliffs or rocks. Avoid slopes steeper than 30 degrees that have recent wind-loading. Seek out slopes sheltered from wind, and consider smaller slopes with clean runouts that minimize the potential size and consequences of a slide.</span></span></span></span></span></span></p>
<p><span><span><span><strong><span><span>Persistent slab avalanches</span></span></strong></span></span></span><span><span><span><span><span><span> are possible with weak, sugary layers of facets and surface hoar buried 1-3 feet deep below the last week’s snow. We have not seen much, if any, recent activity on these layers, and they have shown mixed results in stability tests (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/34085"><span><span><span><span><span><…’s observation from Lionhead</span></span></u></span></span></span></span></span></a><span><span><span><span><span><span>, </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/34067"><span><span><span><span><span><… observation from Cooke</span></span></u></span></span></span></span></span></a><span><span><span><span><span><span>). A couple larger slides near Cooke City a week ago, on </span></span></span></span></span></span><a href="https://www.mtavalanche.com/images/25/avalanche-north-crown-butte"><spa… Butte</span></span></u></span></span></span></span></span></a><span><span><span><span><span><span> and </span></span></span></span></span></span><a href="https://www.mtavalanche.com/images/25/avalanche-east-henderson"><span><… Mtn.</span></span></u></span></span></span></span></span></a><span><span><span><span><span><span>, might have broken on persistent weak layers. These show types of terrain where a larger persistent slab avalanche might be possible and are worth avoiding for now: big slopes that are heavily wind-loaded below prominent ridgelines. Other areas where these weak layers might have been more well preserved are </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/34043"><span><span><span><span><span><…. Ellis</span></span></u></span></span></span></span></span></a><span><span><span><span><span><span>, </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/34080"><span><span><span><span><span><… Rind</span></span></u></span></span></span></span></span></a><span><span><span><span><span><span> and </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/33944"><span><span><span><span><span><… Fork</span></span></u></span></span></span></span></span></a><span><span><span><span><span><span>.</span></span></span></span></span></span></p>
<p><span><span><span><span><span><span>Carefully evaluate the snowpack for recent wind-loading and buried weak layers before getting onto steeper slopes. Throughout the forecast area the avalanche danger is CONSIDERABLE on wind-loaded slopes and MODERATE otherwise.</span></span></span></span></span></span></p>
<p><span><span><span><span><span><span>Special note: At lower elevations around the valleys snow depths are deep, particularly on steep slopes that typically don’t hold much snow and avalanche potential. Dave noted this abundance of snow in Sourdough canyon and made a </span></span></span></span></span></span><a href="https://www.youtube.com/watch?v=LYqruI9gUp0"><span><span><span><span><s…; and </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/34062"><span><span><span><span><span><…; with avalanche concerns and travel advice to keep in mind for these areas.</span></span></span></span></span></span></p>
Upcoming Avalanche Education and Events
Our education calendar is full of awareness lectures and field courses. Check it out: Events and Education Calendar
Two Rider triggered slides in Gravelly Range
Out of Advisory Area
Code
SS-AM-R2-D2
Latitude
44.85020
Longitude
-111.76700
Notes
From FB message: "Two snowmobiler triggered avalanches in Gravelly Range. Riders did not have beacons or rescue equipment. Riders made it out safe luckily."
Number caught
0
Number buried
0
Avalanche Type
Soft slab avalanche
Trigger
Snowmobile
R size
2
D size
2
Problem Type
Wind Slab
Slab Thickness
18.0 inches
Vertical Fall
200ft
Slab Width
200.00ft
Snow Observation Source
Slab Thickness units
inches
Single / Multiple / Red Flag
Multiple Avalanches
Advisory Year