24-25

GNFAC Avalanche Forecast for Tue Dec 31, 2024

Snowpack and Avalanche Discussion

<p>Very dangerous avalanche conditions exist in the Bridger Range north of Bozeman. In the last 36 hours, 27” of snow, equal to 2.8” of SWE, rapidly loaded the snowpack. And it is still snowing. <strong>Persistent slab avalanches </strong>will break deep in the snowpack and propagate across wide areas, and avalanches within the new and wind-drifted snow will be large enough to injure or kill a skier or rider. Yesterday, during the peak storm, a skier on the south side of Bradley’s Meadow was caught by an avalanche; thankfully, they were unharmed (<a href="https://www.mtavalanche.com/node/33144"><strong><span>details</span></s…;).</p>

<p>Natural and human-triggered slides are likely. Traveling in backcountry avalanche terrain is not recommended. Backcountry travelers may trigger avalanches from flat terrain below steeper slopes.</p>

<p><span>The avalanche danger is HIGH on all slopes.</span></p>

<p>A week of snowfall ended yesterday with snow totals measuring in the feet. Significant loading from new and wind-drifted snow results in dangerous avalanche conditions across the forecast area south of Bozeman through Island Park and Cooke City.</p>

<p><strong>Storm Totals from the Last Week: </strong></p>

<ul>
<li>Bridger Range: 34” of snow (3.5” SWE)</li>
<li>Cooke City, Island Park and S. Madison Range: 22-25” of snow (2.5-2.9” SWE)</li>
<li>Lionhead, Northern Madison and Northern Gallatin Range: 19-24” of snow (1.8-2.3” SWE)</li>
</ul>

<p><strong>Persistent slab avalanches </strong>can break across widely across slopes, failing on buried weak layers 1-3 feet deep (deeper on wind-loaded slopes), and avalanches breaking within new and wind-drifted snow, more sensitive to human triggers, will be large enough to bury or injure a rider or skier.</p>

<p><strong>Recent Avalanche Activity:</strong></p>

<ul>
<li>Yesterday, a skier in Cooke City reported several large collapses and a natural avalanche that broke 500 feet wide and 4-6 feet deep high on Henderson Mountain (<a href="https://www.mtavalanche.com/node/33139"><strong><span>photos and details</span></strong></a>)</li>
<li>My partner and I had only skinned twenty minutes in Beehive Basin before triggering an avalanche on a test slope that propagated 150 feet wide, breaking one foot deep (<a href="https://www.mtavalanche.com/node/33133"><strong><span>media and details</span></strong></a>)</li>
<li>Last weekend, we received vague reports of an avalanche that partially buried a rider in the Lionhead area (<a href="https://www.mtavalanche.com/node/32662"><strong><span>details</span></s…;), a snowmobiler triggered slides in Cabin Creek on test slopes (<a href="https://www.mtavalanche.com/node/33083"><strong><span>photos</span></st…;), and Ian and Alex saw a couple of small slides on Lionhead Ridge (<a href="https://www.mtavalanche.com/node/33108"><strong><span>obs and photo</span></strong></a>).</li>
</ul>

<p>Employ cautious route-finding that minimizes exposure to slopes steeper than 30 degrees and avalanche runout zones. Avoid steep wind-loaded terrain in upper mountain bowls and at high elevations.</p>

<p><span>The avalanche danger is CONSIDERABLE. Today, if snowfall exceeds forecast amounts, expect increasing danger.</span></p>

Upcoming Avalanche Education and Events

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

Wednesday, January 8, 2025, 7-9:30 p.m., Avy Savvy Night at the Colonial Theater, Idaho Falls. More information HERE.

Avalanche on Bradleys Meadow Caught and Carried

Bradley Meadow
Bridger Range
Code
ASu
Elevation
7800
Aspect
SE
Latitude
45.83220
Longitude
-110.92800
Notes

From the phone message: A skier on the south side of Bradley's Meadow triggered an avalanche and was caught and carried by the slide. Thankfully, everyone was okay. 

Number of slides
1
Number caught
1
Number buried
0
Trigger
Skier
Trigger Modifier
u-An unintentional release
Slab Thickness units
inches
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

Avalanche on Bradleys Meadow - Skier Caught

Date

From the phone message: A skier on the south side of Bradley's Meadow triggered an avalanche and was caught and carried by the slide. Thankfully, everyone was okay. 

Region
Bridger Range
Location (from list)
Bradley Meadow

large natural avalanche, NE Mt. Henderson

Henderson Mountain
Cooke City
Code
HS-N-R4-D2-O
Elevation
10090
Aspect
NE
Latitude
45.05240
Longitude
-109.94500
Notes

From obs "We were ski touring on the SW side of Mt. Henderson today, and noticed a large (natural?) avalanche on the NE aspect of Henderson.  First observed at around 1:15pm.  It appeared to be very fresh, possibly from a remote trigger this morning.  

2 photos attached.   A NE aspect, around 10,000'.

It looked to be 4-6' deep and about 500' wide.  And it failed on snow at/ near the ground." 

 

From obs: "We popped over to the recent avalanche on the east side and got a crown profile. Avalanche is NE facing, 10090. HS-N-D2-R4-O

Crown is 105 cm deep, breaking on surface hoar. Details are in attached profile 

Something noteworthy.. the slope angle at the crown is 30.1 degrees." 

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Hard slab avalanche
Trigger
Natural trigger
R size
4
D size
2
Bed Surface
O - Old snow
Problem Type
Persistent Weak Layer
Slab Thickness
60.0 inches
Slab Width
500.00ft
Weak Layer Grain type
Surface Hoar
Slab Thickness units
inches
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

We were ski touring on the SW side of Mt. Henderson today, and noticed a large (natural?) avalanche on the NE aspect of Henderson.  First observed at around 1:15pm.  It appeared to be very fresh, possibly from a remote trigger this morning.  

2 photos attached.   A NE aspect, around 10,000'.

It looked to be 4-6' deep and about 500' wide.  And it failed on snow at/ near the ground.

Photo: B Fredlund 

Cooke City, 2024-12-30

We were ski touring on the SW side of Mt. Henderson today, and noticed a large (natural?) avalanche on the NE aspect of Henderson.  First observed at around 1:15pm.  It appeared to be very fresh, possibly from a remote trigger this morning.  

2 photos attached.   A NE aspect, around 10,000'.

It looked to be 4-6' deep and about 500' wide.  And it failed on snow at/ near the ground.

Photo: B Fredlund

Cooke City, 2024-12-30

large natural avalanche, NE Mt. Henderson

Date
Activity
Skiing

We were ski touring on the SW side of Mt. Henderson today, and noticed a large (natural?) avalanche on the NE aspect of Henderson.  First observed at around 1:15pm.  It appeared to be very fresh, possibly from a remote trigger this morning.  

2 photos attached.   A NE aspect, around 10,000'.

It looked to be 4-6' deep and about 500' wide.  And it failed on snow at/ near the ground.

Weather:  today alternated between heavy snowfall, and patches of sunshine.  Temps in the low/ mid 20's F, and calm winds.  A very nice day for ski touring.

No other avalanche activity observed in Miller Creek.

We experienced a couple of large collapses on westerly aspects/ in wind affected terrain around 10,000'.

Region
Cooke City
Location (from list)
Henderson Mountain
Observer Name
Beau Fredlund

Sheep Creek

Sheep Creek
Cooke City
Code
SS-R1-D1
Aspect
N
Latitude
45.03440
Longitude
-109.98400
Notes

From email: "Skied ghost trees in Sheep Creek today. Still a little lean, but mostly good to go for taking clients. Surprised to only see one D1R1 soft Slab on steep north facing slope. No other avalanche activity seen on Miller Mountain, Mineral, Sunset and Republic Mountain. No cr/co." 

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Soft slab avalanche
R size
1
D size
1
Problem Type
Storm Slab
Snow Observation Source
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

Sheep Creek

Date
Activity
Skiing

From email: "Skied in Sheep Creek today. Still a little lean. Surprised to only see one D1R1 soft Slab on steep north facing slope. No other avalanche activity seen on Miller Mountain, Mineral, Sunset and Republic Mountain. No cr/co." 

Region
Cooke City
Location (from list)
Sheep Creek
Observer Name
Ben Zavora