24-25

Transition to Spring in the Centennials

Date
Activity
Skiing

Skied Hellroaring Hut in the Centennials from Friday Mar 28 through Mon Mar 31.

Skied and observed all aspects between 7700' and 10,200' in the vicinity of Mt Jefferson and Reas Peak.

We had good visibility for three days and saw no signs of slab avalanches; no whumphing or cracking; and no signs of blowing or drifting snow (prior to new snow arriving today (Mar 31) snow surface was locked up with solid melt-freeze crusts on all aspects and elevations).

Snow surface starting to show meltwater runnels on S through E aspects below 9000'.

Test pits on N and S aspects at 9100' revealed moist snow under melt-freeze crusts (3" thick breakable crust on N aspects; 10" thick stout crust on S aspects) and no identifiable layers of concern in the upper 130 cm of the snowpack. HS 165 cm on S aspect at 9100' and HS 260 cm on N aspect at 9100'.

We observed pinwheels and predictable wet loose avalanches (D1 to D1.5) on solar aspects above 8000' on Fri and Sat.

Snow started this morning (3/31) and 2.5" of new snow had accumulated when we left at 11:00 a.m. Moderate to strong winds blowing from the south today.

Region
Island Park
Location (from list)
Hellroaring Creek
Observer Name
Alloway

Shooting cracks and wet loose slides

Date
Activity
Snowboarding

Shooting cracks in wind drifted snow on the northwest side of Miller Ridge, and wet loose slides on the southeast side. Very variable out there. 

Region
Cooke City
Location (from list)
Miller Ridge
Observer Name
Noah Mattes

GNFAC Avalanche Forecast for Mon Mar 31, 2025

Snowpack and Avalanche Discussion

<p><span><span><span><span><span><span>Near Bozeman, Big Sky and Cooke City, 9-15” of snow (0.7-1.3” snow water equivalent) fell since Friday and creates the main avalanche problems today. Near Island Park has received 2-3” with heavy snow possible today which will form similar hazards.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>This morning the wind increased out of the southwest and is drifting new snow into thicker slabs which makes </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> possible for people to trigger. Yesterday the wind was calm and the snow was mostly unaffected (</span></span></span></span></span></span><a href="https://www.youtube.com/watch?v=o6qkMwPpVeg&amp;list=PLXu5151nmAvToI_ir… from Mt. Blackmore</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>), so today there is plenty of snow to grow large, fresh slabs which might be easy to trigger.&nbsp;</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Additionally, </span></span></span></span></span></span><span><span><span><strong><span><span>dry loose or wet loose avalanches</span></span></strong></span></span></span><span><span><span><span><span><span> can slide easily on firm melt-freeze crusts buried below the new snow. Any sunshine or above freezing temperatures will quickly make the new snow wet and more cohesive, and increase the chances of larger loose snow slides or </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> on non-wind-loaded slopes.&nbsp;</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Yesterday skiers in the Bridger Range triggered small wind slabs (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/34793"><span><span><span><strong><span…;) and loose snow avalanches (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/34797"><span><span><span><strong><span…;, </span></span></span></span></span></span><a href="https://www.mtavalanche.com/images/25/sluff-debris-pile"><span><span><s…;).</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Assess the stability of the new snow as you travel and watch for changing conditions throughout the day. Be cautious of steep slopes with fresh drifts or a moist snow surface. Cracking across the snow surface is a sign fresh drifts are unstable, and roller-balls or pinwheels indicate a moist snow surface and increasing potential for wet loose slides. Avalanches might not be huge, but even small slides can be harmful if they knock you over a cliff or drag you into trees or rocks. Before riding steep slopes consider the consequences of being caught in any size slide.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Avalanche danger is MODERATE near Bozeman, Big Sky, Cooke City and Island Park.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Near West Yellowstone, 1-3” of snow fell since Friday with a few inches possible today. Small </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 the new snow is drifted into fresh slabs today. Watch for snow blowing across ridgelines, or cracking across the snow surface as signs that fresh drifts exist. Small </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 also possible if the new snow warms up and gets wet. These problems are mainly only an issue where a small slide knocking you off your feet would have high consequences, such as above cliffs or on long, steep slopes.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Aside from small instabilities involving the new snow, the snowpack is generally stable, and large avalanches are unlikely. The avalanche danger is LOW near West Yellowstone.</span></span></span></span></span></span></p>

Hyalite Road Closure 

Starting tonight Hyalite road will be closed to ALL MOTORIZED VEHICLES until the morning of May 16. This is a regular annual road closure to reduce road damage during the spring thaw. Bicycle and foot traffic are allowed. Contact the Bozeman FS Ranger District for more info.

"Skied the north chutes above fairy lake around 8,400 ft. Found 8-12" of new snow, with the bottom 2" consisting of large graupel. In steep terrain our sluff entrained lots of snow making for some large debris piles. Overall the snow was generally well bonded." Photo: S. Lipsteuer

Bridger Range, 2025-03-31

Dry Loose Storm Slabs

Date
Activity
Skiing

Skied the north chutes above fairy lake around 8,400 ft. Found 8-12" of new snow, with the bottom 2" consisting of large graupel. In steep terrain our sluff entrained lots of snow making for some large debris piles. Overall the snow was generally well bonded.

Region
Bridger Range
Location (from list)
Fairy Lake
Observer Name
Spencer Lipsteuer

Broke a small wind slab on Sluice Box

Date
Activity
Skiing

A small wind slab broke as I was skiing down Sluice Box near the weather station on Bridger Ridge. Crown was about 8 feet wide and the slide path looked to be about 60 feet. I was out of its way and unharmed, gave me a pretty good scare though! 

Region
Bridger Range
Location (from list)
Bridger Bowl Weather Station - The Ridge
Observer Name
Karl

Storm snow avalanches on Throne

The Throne
Bridger Range
Code
AS
Elevation
8300
Aspect
N
Aspect Range
N, SE
Latitude
45.88220
Longitude
-110.95200
Notes

The skiing was good and non reactive on the main East face next to the skin track. The North gullies into Naya Nuki creek and the the lower/steeper gullies to the south were highly reactive and entraining lots of snow.

Number of slides
2
Number caught
0
Number buried
0
Trigger
Skier
Problem Type
New Snow
Snow Observation Source
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Multiple Avalanches
Advisory Year

Small wind slabs in Bridgers, Ross Peak

Ross Peak
Bridger Range
Code
SS-AS-R1-D1-S
Elevation
8500
Aspect
NE
Latitude
45.85860
Longitude
-110.95600
Notes

Skied the Banana today with 8-12” of new snow that has mostly bonded. The snowpack below the new snow had froze over night and was well consolidated. 

Observed a layer of graupel (3-4mm grains) at the new/old interface on the NE ramp starting at 8600’ and clearing up after 8700’.  This layer created some reactivity in the storm snow.
Wind slabs <6” had formed on N and NE aspects. We had one small release in the bottom of the couloir measuring ~10x20’ and running ~50’.

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Soft slab avalanche
Trigger
Skier
R size
1
D size
1
Bed Surface
S - Avalanche released within new snow
Problem Type
Wind Slab
Slab Thickness
6.0 inches
Vertical Fall
50ft
Slab Width
15.00ft
Snow Observation Source
Slab Thickness units
inches
Single / Multiple / Red Flag
Single Avalanche
Advisory Year