23-24

GNFAC Avalanche Forecast for Wed Dec 20, 2023

Snowpack and Avalanche Discussion

<p>Trust in a snowpack with a weak structure comes slowly. Persistent weak layers underlying a slab of snow from last week’s storm make human-triggered avalanches possible. Avalanches can break 1-2 feet deep and be large enough to bury or injure backcountry travelers.</p>

<p>Ian and his partner rode at Buck Ridge yesterday and were still able to trigger small slabs of snow immediately adjacent to an avalanche that riders triggered intentionally several days ago on a short, wind-loaded slope. This is clear evidence that some terrain remains unstable (<a href="https://www.youtube.com/watch?v=SpOF7qmKbeU"><strong><span>video</span>…;). Doug and his partner skied north of Bridger Bowl and said, “Even though it’s getting better, I don’t necessarily trust this on all slopes. So, you’re going to want to dig to find out what is happening in the snow… before you drop in and commit” (<a href="https://www.youtube.com/watch?v=iwrE0j4ZjcA"><strong><span>video</span>…;). Skiers at Lionhead Ridge on Monday noted <em>less</em> collapsing than a week before but still observed noticeable signs of instability, including a whumph that propagated 50’ (<a href="https://www.mtavalanche.com/node/29601"><strong><span>observation</span…;). Last weekend, a skier remotely triggered an avalanche at Lionhead Ridge that broke downhill of him on a steep rollover (<a href="https://www.instagram.com/reel/C0-qL5ZrJcd/?id=3260228715764553501_2655…;). Additionally, Alex triggered collapsing in Cooke City (<a href="https://www.youtube.com/watch?v=hugfAvGd09U&amp;list=PLXu5151nmAvSH326z…;), groups in Beehive Basin witnessed cracking, heard whumphs, and got unstable test scores (<a href="https://www.mtavalanche.com/node/29575"><strong><span>details</span></s…;), and two groups triggered collapses and turned back from their objectives in the Bridger Range (<a href="https://www.mtavalanche.com/node/29570"><strong><span>details1</span></…;, <a href="https://www.mtavalanche.com/node/29582"><strong><span>details2</span></…;). Look at the long list of documented instabilities on the <a href="https://www.mtavalanche.com/weather/wx-avalanche-log"><strong><span>wea… and avalanche log</span></strong></a> for a more complete picture.</p>

<p>As I mentioned in my <a href="https://www.youtube.com/watch?v=hN3auEiOfbU"><strong><span>video</span>…; from the Throne on Monday, we have two options for safer backcountry travel. Either continue avoiding avalanche terrain <em>or </em>dig, test, and turn back to lower-angle slopes if you observe any signs of instability. Follow the principles of safe travel by carrying rescue gear and never exposing more than one person at a time to steeper slopes.</p>

<p>The avalanche danger is MODERATE.</p>

Upcoming Avalanche Education and Events

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

Roller balls in Hyalite

Date
Activity
Ice Climbing

Roller balls even on NE slopes around noon. Roughly 8000’ up Hyalite. Yuck. It’s hot. 

Region
Northern Gallatin
Location (from list)
Hyalite - main fork
Observer Name
matt zia

Snowmobile Triggered Avalanche on Buck Ridge

Buck Ridge
Northern Madison
Code
HS-AM-R2-D1-O
Elevation
9400
Latitude
45.17190
Longitude
-111.38000
Notes

An avalanche along the divide between Muddy and Bear Creek. Avalanche was approximately 100 ft wide and 25 ft tall, breaking on facets just above a crust near the ground. Slide was clearly several days old, estimating it broke Friday, 12/15/23. Tracks indicate it was likely snowmobile triggered. Photo taken 12/19/23. GNFAC

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Hard slab avalanche
Trigger
Snowmobile
R size
2
D size
1
Bed Surface
O - Old snow
Problem Type
Persistent Weak Layer
Slab Thickness
18.0 inches
Vertical Fall
25ft
Slab Width
100.00ft
Weak Layer Grain type
Faceted Crystals
Weak Layer Hardness
F
Slab Layer Grain Type
Decomposing and Fragmented precipitation particles
Slab Layer Hardness
1F
Slab Thickness units
inches
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

An avalanche along the divide between Muddy and Bear Creek. Avalanche was approximately 100 ft wide and 25 ft tall, breaking on facets just above a crust near the ground. Slide was clearly several days old, estimating it broke Friday, 12/15/23. Photo taken 12/19/23. GNFAC

Northern Madison, 2023-12-19