24-25

GNFAC Avalanche Forecast for Fri Apr 11, 2025

Snowpack and Avalanche Discussion

<p><span><span><span><span><span><span>With temperatures already above freezing this morning, sunny skies, and temperatures rising into the 50s F today,</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> are the primary avalanche concern. With clear skies overnight, some areas will likely have thin crusts at the surface, but those will break down quickly in today’s intense mid-April sun. Wet Loose avalanches will mostly be confined to the snow that fell on Tuesday, sliding on the firm crusts beneath. Don’t discount the power of these relatively small slides - even a slide a few inches deep can entrain a lot of snow and take you for quite an unpleasant ride. Wet loose avalanches will either start at your feet or could come down from above you from near exposed rocks on steep, sunny slopes. Plan to move off steep, sunny slopes as the day heats up and there are more than a couple inches of wet snow at the surface.</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 still possible on shady, high elevation slopes with colder, drier snow. On Wednesday, there were natural and skier triggered wind slabs in the Bridgers and near Big Sky (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/34888"><span><span><span><strong><span…;, </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/34894"><span><span><span><strong><span…;). Another 48 hours of warm temperatures have likely glued most of these slabs on, but be on the lookout for the slopes where they haven’t. Cracks shooting out in front of your skis or snowmobile are bullseye information that drifts remain unstable. Consider keeping things simple by just steering around wind drifts.&nbsp;</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>After a night with no freeze,</span></span></span></span></span></span><span><span><span><strong><span><span> Cornices </span></span></strong></span></span></span><span><span><span><span><span><span>breaking off are another concern. Minimize time spent below them 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>

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