24-25

GNFAC Avalanche Forecast for Sun Feb 23, 2025

Snowpack and Avalanche Discussion

<p><span><span><span><span><span><span>A person can trigger large avalanches that break on weak layers buried 1-3 feet deep. These </span></span></span></span></span></span><span><span><span><strong><span><span>persistent slab avalanches</span></span></strong></span></span></span><span><span><span><span><span><span> can break hundreds of feet wide, and can be tricky as they might be triggered by the first person, or after multiple people have ridden a slope.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>On Friday in the southern Madison Range there were multiple rider triggered persistent slab avalanches, one of which partially buried a rider in Tepee Basin and was triggered after their group had put multiple tracks on the slope (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/34301"><span><span><span><span><span><… and photos</span></span></u></span></span></span></span></span></a><span><span><span><span><span><span>). Fortunately his arm and leg were visible and his partners got him out quickly and unharmed. Nearby, in the Taylor Fork, I triggered a “whumph” with a 100 ft long crack (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/34298"><span><span><span><span><span><…;), and a group of riders triggered a few avalanches from flat terrain above a steep slope (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/34327"><span><span><span><span><span><…;).&nbsp;</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Although the likelihood and danger has decreased, the potential large consequences of these avalanches remain unchanged. Be cautious of slopes steeper than 30 degrees, particularly at middle and lower elevations, as many of these slides are happening on mid elevation slopes with trees around (</span></span></span></span></span></span><a href="https://www.youtube.com/watch?v=tAiSHSEDJhY&amp;t=1s"><span><span><span… video</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/34264"><span><span><span><span><span><… Canyon photos</span></span></u></span></span></span></span></span></a><span><span><span><span><span><span>).&nbsp;</span></span></span></span></span></span></p>

<p><span><span><span><strong><span><span>Wind Slab avalanches</span></span></strong></span></span></span><span><span><span><span><span><span> are an additional concern. Although their potential size is relatively small, watch for fresh drifts that grow from today’s winds and old drifts that haven’t bonded yet.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Large, human-triggered avalanches are possible and avalanche danger is MODERATE.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Across the rest of the forecast area </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>can be triggered where strong wind the last couple days drifted snow into stiff slabs (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/images/25/wind-slab-hardscrabble"><span><sp…;).&nbsp;</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Near Cooke City and Island Park, today’s new snow and wind will create larger drifts that might be easy to trigger. Depending on how much snow falls during the day, by this afternoon </span></span></span></span></span></span><span><span><span><strong><span><span>storm slab avalanches</span></span></strong></span></span></span><span><span><span><span><span><span> could become a problem on slopes where snow is not drifted. Warming temperatures might create density changes within the new snow that make avalanches easier to trigger. If there is more than 6” of new snow be cautious of all steep slopes, especially where even a small slide could push you into trees or over cliffs.</span></span></span></span></span></span></p>

<p><span><span><span><strong><span><span>Wet loose avalanches</span></span></strong></span></span></span><span><span><span><span><span><span> are possible where above freezing temperatures melt the snow surface and make it sticky and wet. This is more likely near Bozeman and Big Sky where temperatures are warmer and there is a chance of light rain at lower elevations. Be careful of steep slopes with a wet snow surface.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Assess the snowpack for new and old drifts or a wet snow surface, and be extra cautious if there is heavy snowfall today. Human-triggered avalanches are possible and the avalanche danger is MODERATE.</span></span></span></span></span></span></p>

<h3><span><span><span><strong><span><span>Special Note - Roof avalanches</span></span></strong></span></span></span></h3>

<p><span><span><span><span><span><span>Many roofs have lots of snow on them that may come crashing down as a roof avalanche during the first big warm-up with strong sunshine. Avalanche fatalities from roof avalanches are not uncommon. Kids are especially vulnerable because they often play near houses while no one is watching.</span></span></span></span></span></span></p>

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Test scores, poor structure near Maverick Mt

Date
Activity
Skiing

Dug in the snow with the Dillon Fundamentals course at Maverick today. Pit was NE facing Slope off Thin Air run @ 7770' When I stepped out of my skis I sunk all the way to the ground..

Snow was 90-100cm deep, with 45 cm new snow over a faceted lower half of the snowpack. Facets at 40cm above ground were 1-2mm and near the ground larger facets were mixed with wet depth hoar 4-5mm. We observed an ECTN22 @ 40cm on the smaller facets and an ECTP23 near the ground. 

We avoided travel on solar slopes due to breakable crust, and mostly kept to the ski area. Did not observe any recent avalanches. 

Region
Dillon Area
Location (from list)
Maverick Mountain
Observer Name
S Regan

Snowmobiler triggered avalanches in Taylor Fork

Taylor Fork
Southern Madison
Code
HS-AMr-R2-D2-O
Elevation
9000
Aspect
SW
Latitude
45.06070
Longitude
-111.27200
Notes

From IG message: "We remotely triggered this hillside in Taylor's fork yesterday [2/21] from the Ridgeline above it. We were looking for a safe spot to drop down when it released below us. Circled around for some pictures. The snow was pretty shallow, only 2-3 feet deep, and slid to the ground. South facing slope"

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Hard slab avalanche
Trigger
Snowmobile
Trigger Modifier
r-A remote avalanche released by the indicated trigger
R size
2
D size
2
Bed Surface
O - Old snow
Problem Type
Persistent Slab
Slab Thickness
24.0 inches
Vertical Fall
125ft
Slab Width
100.00ft
Slab Thickness units
inches
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

From IG message: "We remotely triggered this hillside in Taylor's fork yesterday [2/21] from the Ridgeline above it. We were looking for a safe spot to drop down when it released below us. Circled around for some pictures. The snow was pretty shallow, only 2-3 feet deep, and slid to the ground. South facing slope"

Southern Madison, 2025-02-23

From IG message: "We remotely triggered this hillside in Taylor's fork yesterday [2/21] from the Ridgeline above it. We were looking for a safe spot to drop down when it released below us. Circled around for some pictures. The snow was pretty shallow, only 2-3 feet deep, and slid to the ground. South facing slope"

Southern Madison, 2025-02-23

From IG message: "We remotely triggered this hillside in Taylor's fork yesterday [2/21] from the Ridgeline above it. We were looking for a safe spot to drop down when it released below us. Circled around for some pictures. The snow was pretty shallow, only 2-3 feet deep, and slid to the ground. South facing slope"

Southern Madison, 2025-02-23

Small wet loose slides in Bridgers

The Throne
Bridger Range
Code
WL-N-R1-D1
Elevation
8000
Aspect
S
Latitude
45.88220
Longitude
-110.95200
Notes

"...We saw a handful of small point releases on steep south slopes, likely from Friday, but no other recent avalanche activity.  By mid-day/early afternoon, the snow lower down in the woods was getting pretty heavy and wet and anywhere with the slightest bit of sun exposure was developing a crust..."

Number of slides
3
Number caught
0
Number buried
0
Avalanche Type
Wet loose-snow avalanche
Trigger
Natural trigger
R size
1
D size
1
Problem Type
Loose Wet
Snow Observation Source
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Multiple Avalanches
Advisory Year

Natural wind slabs in N. Bridgers

Hardscrabble Peak
Bridger Range
Code
HS-N-R2-D1.5-I
Elevation
9000
Aspect
NE
Latitude
45.91510
Longitude
-110.98100
Notes

From obs: "Saw a recent cornice triggered wind slab off of Hardscrabble Peak, crown looked fairly fresh. There was a second crown line below the rock band. Conditions were very windy, with snow still being transported. Most snow surfaces were wind affected, but saw no cracking or collapsing."

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Hard slab avalanche
Trigger
Natural trigger
R size
2
D size
1.5
Bed Surface
I - Interface between new and old snow
Problem Type
Wind Slab
Slab Thickness
12.0 inches
Slab Width
30.00ft
Snow Observation Source
Slab Thickness units
inches
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

From obs.: "Saw a recent cornice triggered wind slab off of Hardscrabble Peak, crown looked fairly fresh. There was a second crown line below the rock band. Conditions were very windy, with snow still being transported. Most snow surfaces were wind affected, but saw no cracking or collapsing." Photo: F. Miller

Bridger Range, 2025-02-23

Cornice triggered persistent slab in Suce Creek

Other place
Out of Advisory Area
Code
ACc-R2-D2-O
Aspect
N
Latitude
45.65530
Longitude
-110.55800
Notes

From IG story. "Cornice triggered persistent on a protected north face up Suce Creek. 3-4 ft deep. Absarokas are not like the Bridgers, Gallatins, etc. A few weeks ago we found the entire snowpack to be faceted top to bottom in Mill Creek...."

Number of slides
1
Number caught
0
Number buried
0
Trigger
Cornice fall triggered by human or explosive action
Trigger Modifier
c-A controlled or intentional release by the indicated trigger
R size
2
D size
2
Bed Surface
O - Old snow
Problem Type
Persistent Slab
Slab Thickness
36.0 inches
Snow Observation Source
Slab Thickness units
inches
Single / Multiple / Red Flag
Single Avalanche
Advisory Year