23-24

New snow and weak layers

Date

We rode up to the head of Yale Creek, down a bit into the head of Hellroaring Creek and then returned via the East Fork of Hotel Creek. The depth of new snow increased dramatically with elevation from approximately 8" (0.5" SWE) at 8000 ft to 18" (0.7" SWE) at 9000 ft. The new snow had little cohesion. 

We found buried surface hoar on both shady and sunny slopes. Sunny slopes had multiple melt-freeze crusts interspersed with weak facets throughout the pack. On shady slopes the lower snowpack was entirely faceted. We had an ECTP11 on facets just below the old snow surface on a S facing slope. Otherwise our results were ECTX and ECTN with slab fracture in Propagation Saw Tests (likely because neither the facets or new snow were cohesive enough to act as a slab in our tests).

Wind, settlement or more snow could quickly make for a cohesive slab. When that happens, with so much new snow and such weak snow beneath it conditions will rapidly become unstable. 

We saw no avalanche activity and had no cracking or collapsing. 

Region
Island Park
Location (from list)
Yale Creek
Observer Name
Ian Hoyer

New Snow at the Ramp

Date
Activity
Skiing

We went to Bridger Bowl today and walked along the ridge to the Ramp. The west wind was calm and there wasn't any new snow being transported while we were walking. Snow remained mostly light (S1) with short bursts where snowfall increased (S2). We stopped at the top of Lazy Susan to dig, we found 6" of new snow sitting over old weak snow. Despite being just below the ridge this area was not wind-loaded and we found a well-preserved layer of 10-15mm surface hoar. We had no results in stability tests, ECTX HS: 78 cm. During the descent of the ramp we triggered multiple sloughs in the new snow however they did not run far and were not big. 

Region
Bridger Range
Location (from list)
The Ramp
Observer Name
Zach Peterson

Hyalite Tour

Date
Activity
Skiing

From email: "Made it to the ridge of Hyalite peak yesterday. Mild winds ~10mph at around 1pm. Seemed to be ~6" of fresh snow in the basin. No instabilities in our pit at 9300ft; fist hardness throughout. 85cm depth. Great skiing in the basin. Off the ridge, it was a little firmer with a wind crust. There was a small natural wind slab avalanche on an east aspect a few hundred feet SW of the saddle."

Region
Northern Gallatin
Location (from list)
Hyalite Peak
Observer Name
Patrick Honsinger

GNFAC Avalanche Forecast for Sun Jan 7, 2024

Snowpack and Avalanche Discussion

<p><span><span><span><span><span><span>Today avalanches can be triggered on wind-loaded slopes where the new snow was drifted into thicker slabs. These slabs are 4-12” deep and sitting on a very weak snowpack which is causing them to break easily and propagate wide. Watch for signs of recent wind-loading such as cornices, rounded smooth pillows of snow and snow surfaces with wavy textures. Be extra cautious of slopes that appear wind-loaded. Cracking across the surface of the snowpack is a sign you have found an unstable drift that will slide on steep slopes.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Additionally, the weak snowpack is contributing to large dry loose avalanches on long, sustained steep slopes (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/images/24/dry-loose-avalanches-weak-facets"… from Buck Ridge</span></span></u></span></strong></span></span></span></a><span><span><span><strong><span><span>, </span></span></strong></span></span></span><a href="https://www.mtavalanche.com/images/24/skier-triggered-loose-snow-avalan… from Beehive</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>, </span></span></span></span></span></span><a href="https://www.mtavalanche.com/images/24/loose-snow-avalanche-henderson"><… from Cooke</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>). These ”facet sloughs” carry plenty of force to knock you over as they entrain almost the entire snowpack. Yesterday at Buck Ridge we saw a fresh natural avalanche and easily intentionally triggered a few shallow wind slabs and long running facet sloughs (</span></span></span></span></span></span><a href="https://www.youtube.com/watch?v=Y0LROtnc7Us&amp;list=PLXu5151nmAvSH326z…;, </span></span></strong></span></span></span><a href="https://www.mtavalanche.com/node/29802"><span><span><span><strong><span… slab photos</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>,</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/29799"><span><span><span><span><span><…; </span></span></u></span></span></span></span></span><span><span><span><strong><span><u><span><span>natural avalanche photos</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>).&nbsp;</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Near West Yellowstone and Island Park, where up to 9” of low density snow fell (0.3” of snow water equivalent), larger avalanches are possible. In general, current avalanche concerns are small and easy to identify, but they point to a very unstable snowpack. The weak snowpack could cause avalanches to break above you, wider or larger than expected. Any size slide can get you into trouble if it carries you into trees, over cliffs or rocks, or piles up deeper in a confined gully.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Before crossing steep slopes, carefully assess the snowpack for signs of wind-loading and consider the consequences of an avalanche. Today the avalanche danger is MODERATE throughout the forecast area.</span></span></span></span></span></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.

Hyalite conditions

Date
Activity
Skiing

We toured up into the Maid today to see how conditions were looking. Low snow down low and starting to stack up in the basins. We dug a pit on a East aspect at 9500, the pit showed a 100cm deep snowpack. Large facets were found from the ground up to 40cm. There was a hard crust layer at 40cm, above the crust layer was a dense slab that hasnt turned completely rotten yet. The snowpack was dense above the crust layer, but less consolidated towards the surface (upside down). We had an ECTN 21 at 40cm. We also observed numerous wind slabs that relaeased naturally during the day on N-NE aspects near ridgelines (6-12 inch crowns). We also found touchy wind slabs on micro terrain lower in the basin. 

Region
Northern Gallatin
Location (from list)
Maid of the Mist
Observer Name
Tommy S

Remotely Triggered Avalanches, Buck Ridge

Buck Ridge
Northern Madison
Code
SS-AFr-R1-D1-I
Elevation
9400
Aspect Range
E-NE
Latitude
45.17190
Longitude
-111.38000
Notes

While approaching a test slopes riders remotely triggered two 6-12" deep wind slabs. The first was on a NE-facing slope and the second at a E-facing slope both above Muddy Creek at 9400'. The first of these broke on a layer of buried surface hoar below recent snow. 

Number of slides
2
Number caught
0
Number buried
0
Avalanche Type
Soft slab avalanche
Trigger
Foot penetration
Trigger Modifier
r-A remote avalanche released by the indicated trigger
R size
1
D size
1
Bed Surface
I - Interface between new and old snow
Problem Type
Wind Slab
Slab Thickness
6.0 inches
Weak Layer Grain type
Surface Hoar
Snow Observation Source
Slab Thickness units
inches
Single / Multiple / Red Flag
Multiple Avalanches
Advisory Year