24-25

Date

Sun, 02/23/2025 - 15:40

Activity

Snowmobiling

We got to ride into Tepee Basin with a pair of snowmobilers who were involved in an avalanche two days ago (2/23). The pair generously offered to join us and run us through the incident. It was an incredible opportunity to learn from each other. Read details about the slide.

The avalanche failed on the weak layer of facets that formed in late January. We also spotted another avalanche in similar, mid-elevation terrain likely triggered yesterday or earlier this morning. Both of these avalanches fit the pattern we've been seeing in Lionhead and the recent slide outside the forecast area in the Black Canyon area of Island Park. Other than the Black Canyon avalanche which is uncertain because we have not visited the site, the slides are taking place in mid-elevation terrain, smaller slopes with minimal wind-loading, and a thinner snowpack.

The snowpack in both the Tepee slides was thin relative to the average snowpack depth (129 cm).

Take Homes:

You aren't good to go if you avoid the steep, upper-elevation, wind-loaded bowls. Steep slopes at mid-elevations harbor weak snow and have the potential for an avalanche.
The persistent slab avalanche problem is alive and well. The epicenter of this problem is in the Lionhead area and the Southern Madison and Southern Gallatin Ranges.

Region

Southern Madison

Location (from list)

Tepee Basin

Observer Name

Zinn and Staples

Read more about Tepee Basin Avalanche Profile - 23 February 2025

Southern Madison, 2025-02-23

Access other image sizes:

Big Belts

Date

Fri, 02/21/2025 - 16:00

Activity

Skiing

Observation up in Big Belts North of Baldy, by the Hut meadow. 8600FT, 22 Deg Slope, NorthEast Slope. Open Meadow.

46.46385, -111.24431

Snow Depth, 225Cm+

Windy as hell. Thur - Sunday 40-70MPH above treeline from SW to W to South.

ECTN20 @195CM. Slabby Conditions from wind deposition but generally right side up snow.

Significant crowns in vicinity 2-6ft deep 200ft lengths in the steep E Facing bowls nearby.

Region

Out of Advisory Area

Observer Name

J Budreski

GNFAC Avalanche Forecast for Sun Feb 23, 2025

Snowpack and Avalanche Discussion

A person can trigger large avalanches that break on weak layers buried 1-3 feet deep. These persistent slab avalanches 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.

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 (<a href="https://www.mtavalanche.com/node/34301"><… and photos</a>). 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 (<a href="https://www.mtavalanche.com/node/34298"><…;), and a group of riders triggered a few avalanches from flat terrain above a steep slope (<a href="https://www.mtavalanche.com/node/34327"><…;).

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 (<a href="https://www.youtube.com/watch?v=tAiSHSEDJhY&t=1s"><span… video</a>, <a href="https://www.mtavalanche.com/node/34264"><… Canyon photos</a>).

Wind Slab avalanches 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.

Large, human-triggered avalanches are possible and avalanche danger is MODERATE.

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

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 storm slab avalanches 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.

Wet loose avalanches 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.

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.

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

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.

Read more about GNFAC Avalanche Forecast for Sun Feb 23, 2025

Upcoming Avalanche Education and Events

Our education calendar is full of awareness lectures and field courses. Check it out: Events and Education Calendar

Test scores, poor structure near Maverick Mt

Date

Sat, 02/22/2025 - 12:00

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

2/21/2025

Code

HS-AMr-R2-D2-O

Elevation

9000

Aspect

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

Number caught

Number buried

Avalanche Type

Hard slab avalanche

Trigger

Snowmobile

Trigger Modifier

r-A remote avalanche released by the indicated trigger

R size

D size

Bed Surface