22-23

Weak Layers and Wind Slabs - Saddle Peak

Date
Activity
Skiing

We hiked the ridge to Football Field. We dug just below the ridge and found a couple of problems in our pit. A 15-20 cm (6-8”) wind slab had formed over the last few days. The HS was 110 cm, and we got an ECTP12, below that wind drifted snow (11 cm down from surface). Next, we got an ECTP 21 and 28 in the middle of the snowpack (56 cm down from surface). The ECTP21 and 28 occurred on 1-2 mm facets sitting below a pencil hard layer of rounded grains.

Region
Bridger Range
Location (from list)
Saddle Peak
Observer Name
GNFAC

Poor test scores and heavy wind transport

Date
Activity
Skiing
Snowboarding

ECTP25Q1 on a layer of well developed facets about 30cm from the ground on an easterly aspect at 9200 feet. Pit was approx 75cm deep.

 

Observed heavy active wind transport from westerly aspects to easterly aspects.

 

Larger, 1.5-2mm facets were found in our westerly pit at 9100 feet but not reactive in tests. It was enough for us to not consider descending avalanche terrain. 

Region
Northern Madison
Location (from list)
Beehive Basin
Observer Name
Katrina R.

Encouraging test scores on Shedhorn Mountain

Date
Activity
Skiing

My partner and I snowmobiled into the Taylor fork up to the base of Shedhorn Mountain where we began ascending the E aspect on skis. On the way up,  SW winds were gusting in the moderate range  and there was active wind loading visible on the ridgeline. We chose to make our way up one of the main avalanche paths and observed a definitive faceted weak layer below more recent new snow. In November, I had observed this weak layer while it was forming, so I was not surprised to find it.

On a due east aspect at 8972', we chose to dig a quick test pit in lower angle terrain before traveling higher on the slope and exposing ourselves to the steeper avalanche terrain above that had evidence of somewhat recent D1-1.5 avalanches. Our pit showed a snow depth of 80cm and a definitive weak layer below recent new snow. Our results were encouraging, ECTN16, and we skinned up to treeline and skied the lower angle slopes below.  

Region
Southern Madison
Location (from list)
Taylor Fork
Observer Name
Eric Heiman

GNFAC Avalanche Forecast for Sun Dec 11, 2022

Snowpack and Avalanche Discussion

<p><span><span><span><span><span><span>More new snow and southerly wind today will create dangerous avalanche conditions. Weak layers buried 2-3 feet deep will be under additional stress from the weight of new snow, especially where snow is drifted into thicker slabs (</span></span></span></span></span></span><a href="https://www.youtube.com/watch?v=35NYGUBLhbg&amp;t=5s"><span><span><span… avalanche video</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>). Human-triggered avalanches are likely, and may be triggered from lower angle terrain below steep slopes. Avoid steep slopes, especially slopes that are wind-loaded, and give them a wide berth if crossing beneath them. Avalanche danger is CONSIDERABLE.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Near Cooke City it is possible to trigger a large avalanche, breaking more than 3 feet deep on buried weak layers. These mountains will not receive much snow today and southerly wind has decreased. This will decrease the likelihood of triggering a large avalanche, but the consequences remain large. On Friday, my partner and I triggered an avalanche that broke 3-6 ft deep and 500 feet above us while we were crossing below a steep slope near Lulu Pass (</span></span></span></span></span></span><a href="https://www.youtube.com/watch?v=7sKzKPXI1dM"><span><span><span><strong>… href="http://www.mtavalanche.com/images/22/fisher-avalanche-full-extent">phot…;). My partner was carried, but not buried and was uninjured. This was only the latest in a string of large natural and human triggered avalanches over the last week (</span></span></span></span></span></span><a href="https://www.youtube.com/watch?v=N8CtHy3efxs"><span><span><span><strong>… Pass video</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/27113"><span><span><span><strong><span… photo and details</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>). If you plan to travel on or below steep slopes, carefully assess the snowpack for buried weak layers and wind-loading, and consider the consequences of triggering a large avalanche. The avalanche danger is MODERATE.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Yesterday, moderate to strong south-southwest wind blew 2-4” of recent snow into thick drifts that can avalanche under the weight of a person. Snowmobilers on Buck Ridge reported a cornice triggered avalanche (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/27160"><span><span><span><strong><span… and details</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>), skiers in the Bridger Range triggered fresh wind slabs (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/27169"><span><span><span><strong><span… and details</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>), and skiers in Hyalite saw a powder cloud from a cornice fall or wind slab in the Main Fork (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/images/22/cornice-fall-or-slide-hyalite"><s…;) and a recent wind slab on Mt. Blackmore (<a href="https://www.mtavalanche.com/images/22/small-slide-blackmore"><strong>ph…;). Doug was climbing in Hyalite on Friday and found a 10” deep wind slab sitting over a thin weak layer (</span></span></span></span></span></span><a href="https://www.youtube.com/watch?v=rRbw4FFs4i0"><span><span><span><span><s… gullies video</span></span></u></span></span></span></span></span></a><span><span><span><span><span><span>). A setup like this will make drifts possible to trigger. Before crossing or riding steep slopes, carefully assess the snowpack for wind slabs resting over weak layers and consider the consequences of even a small slide. The avalanche danger is MODERATE.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>If you get out, please share avalanche, snowpack or weather observations via our</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/add/snow_obs"><span><span><span><span>…; </span></span></span></span></span></span><span><span><span><strong><span><u><span><span>website</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>, email (</span></span></span></span></span></span><span><span><span><strong><span><span>mtavalanche@gmail.com</span></span></strong></span></span></span><span><span><span><span><span><span>), phone (406-587-6984), or Instagram (#gnfacobs).</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Heavy snowfall and strong winds make for dangerous avalanche conditions today. Two days ago, Dave and Ian found up to 18” of new snow while riding in Yale Creek and drifts up to 4 ft deep (</span></span></span></span></span></span><a href="https://www.youtube.com/watch?v=06pszOXXgOQ"><span><span><span><strong>… video</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>). They also found weak layers similar to what we’ve seen in Lionhead (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/27153"><span><span><span><strong><span… observations</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>). Avoid steep slopes today and give them a wide berth if you’re crossing beneath them. Stick to low angle slopes and enjoy the fresh snow. Human triggered avalanches are likely.</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.

On Dec 9, 2022 around 1:30pm we triggered this avalanche while riding across the lower angle slope below. It broke 3-6+' deep and 300' wide. One rider was caught and carried, and luckily nobody was injured. Photo from 12/10: GNFAC

Cooke City, 2022-12-11

Large slough or slide in Hyalite

Date
Activity
Skiing

Large slough or slide in Hyalite today. Taken from Lick Creek. Looks like either land of the lost or avalanche gulch

Region
Northern Gallatin
Location (from list)
Hyalite - main fork
Observer Name
Jerry Johnson