24-25

GNFAC Avalanche Forecast for Thu Apr 10, 2025

Snowpack and Avalanche Discussion

<p><span><span><span><span><span><span>The main avalanche concern is </span></span></span></span></span></span><span><span><span><strong><span><span>wet loose avalanches</span></span></strong></span></span></span><span><span><span><span><span><span> due to above freezing temperatures and sunshine that will make the snow surface wet and non-cohesive. Snow that fell on Tuesday will quickly become moist and slide easily on firm crusts underneath. Larger slides are possible where more snow fell on Tuesday. Wet loose slides even just a few inches deep can easily knock you over, entrain a lot of snow, run long distances and pack a powerful punch if you get caught in one. Natural wet loose slides will initiate near rock outcrops on steep, sunny slopes. Pay attention to what is above you and avoid or minimize time spent on and below steep sunny slopes, especially during the heat of the day. Look for slopes with colder drier snow, and plan to be off and out from below steep slopes before the snow surface becomes moist or wet.</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. Moderate to strong westerly wind drifted recent snow into stiffer slabs that are possible for a person to trigger. Yesterday, Dave saw natural wind slab avalanches in the Bridger Range (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/34888"><span><span><span><strong><span…;), and near Big Sky skiers triggered some 1 foot deep slabs with a small cornice drop (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/34894"><span><span><span><strong><span…;). Although relatively small, these slabs can easily carry you down a steep slope. Watch for a textured or rounded snow surface as signs of recent wind slabs. Cracks shooting across the snow from your skis or snowmobile are a sign recent drifts are unstable. Be cautious of wind-loaded slopes, especially where a slide could drag you into rocks, trees or over cliffs.</span></span></span></span></span></span></p>

<p><span><span><span><strong><span><span>Cornices </span></span></strong></span></span></span><span><span><span><span><span><span>along ridgelines</span></span></span></span></span></span><span><span><span><strong><span><span> </span></span></strong></span></span></span><span><span><span><span><span><span>will weaken with the heat and could break on their own or under the weight of a person. Minimize time on slopes below cornices, and stay far back from the edge while traveling along ridgelines.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>The avalanche danger is MODERATE throughout the forecast area.</span></span></span></span></span></span></p>

Hyalite Road Closure 

Wind slabs in N. Madison

Northern Madison
Code
SS-NCc-R1-D1.5
Notes

Found some reactive fresh windslabs that were on northeast terrain  features yesterday Wednesday 4/9 easily triggered with a very small cornice we dropped in the northern Madison range, the pocket slabs didn’t propagate super wide but did pack a punch and were up to 1 ft deep.

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Soft slab avalanche
Trigger
Cornice fall
Trigger Modifier
c-A controlled or intentional release by the indicated trigger
R size
1
D size
1.5
Problem Type
Wind Slab
Slab Thickness
12.0 inches
Snow Observation Source
Slab Thickness units
inches
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

Reactive fresh wind slabs in N. Madison

Date

Found some reactive fresh windslabs that were on northeast terrain  features yesterday Wednesday 4/9 easily triggered with a very small cornice we dropped in the northern Madison range, the pocket slabs didn’t propagate super wide but did pack a punch and were up to 1 ft deep.

Region
Northern Madison

Thin Wind Slab Avalanche near Hardscrabble

Fairy Lake
Bridger Range
Code
SS-N-R1-D1-I
Elevation
9000
Aspect
SE
Latitude
45.90430
Longitude
-110.95800
Notes

I rode into Fairy Lake. There was 2-3” of new snow above the elevation of Fairy Lake, a trace below. Winds were cranking at ridge top elevation, transporting what soft snow there was. Minimal hazard formation. I spotted one fresh wind slab avalanche near Hardscrabble. The slide ran several hundred feet in steep terrain but was very thin (R1,D1). 

There was a mostly supportable crust below the new snow about 1” thick. The snow below the crust was moist. 

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Soft slab avalanche
Trigger
Natural trigger
R size
1
D size
1
Bed Surface
I - Interface between new and old snow
Problem Type
Wind Slab
Slab Thickness
3.0 inches
Vertical Fall
200ft
Slab Width
150.00ft
Snow Observation Source
Slab Thickness units
inches
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

Winds were cranking at ridge top elevation, transporting what soft snow there was. Minimal hazard formation. I spotted one fresh wind slab avalanche near Hardscrabble. The slide ran several hundred feet in steep terrain but was very thin (R1,D1). Photo: GNFAC

Bridger Range, 2025-04-09

Thin Wind Slab Avalanche Hardscrabble

Date
Activity
Snowmobiling

I rode into Fairy Lake. There was 2-3” of new snow above the elevation of Fairy Lake, a trace below. Winds were cranking at ridge top elevation, transporting what soft snow there was. Minimal hazard formation. I spotted one fresh wind slab avalanche near Hardscrabble. The slide ran several hundred feet in steep terrain but was very thin (R1,D1). 

There was a mostly supportable crust below the new snow about 1” thick. The snow below the crust was moist. 

Region
Bridger Range
Location (from list)
Fairy Lake
Observer Name
Dave Zinn

GNFAC Avalanche Forecast for Wed Apr 9, 2025

Snowpack and Avalanche Discussion

<p><span><span><span><span><span><span>New snow that fell yesterday creates a couple avalanche problems to watch for. </span></span></span></span></span></span><span><span><span><strong><span><span>Wet loose avalanches</span></span></strong></span></span></span><span><span><span><span><span><span> will be easy to trigger when the new snow gets wet from sun and above freezing temperatures. These slides will be larger where there is more new snow, and even just a few inches of wet snow sliding can easily knock you over. These slides are somewhat predictable and typically start right at your skis, feet or sled, making them relatively easy to avoid. However, they can entrain a lot of snow, run long distances and pack a powerful punch if you get caught in one. Plan to be off and out from below steep slopes before the snow surface is moist or wet.</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 also possible where westerly winds drift the new snow into stiffer slabs. Increasing winds later today will continue to grow fresh drifts. Watch for snow blowing off ridgelines, or a textured or rounded snow surface as signs of fresh wind slabs. Cracks shooting across the snow from&nbsp; your skis or snowmobile are a sign fresh drifts are unstable. Be cautious of wind-loaded slopes, especially where a slide could drag you into rocks, trees or over cliffs.</span></span></span></span></span></span></p>

<p><span><span><span><strong><span><span>Cornice falls</span></span></strong></span></span></span><span><span><span><span><span><span> are an additional concern to keep in mind. These will become an increasing concern over the next couple days of hotter temperatures and sun. Minimize time on slopes below cornices, especially during the heat of the day, and stay far back from the edge while traveling along ridgelines.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Carefully evaluate the stability of the new snow before traveling on steep slopes. The avalanche danger is MODERATE near Bozeman, Big Sky, West Yellowstone, Island Park and Cooke City.</span></span></span></span></span></span></p>

Hyalite Road Closure