24-25

Warm at the Maid

Date
Activity
Skiing

We got into the Maid basin around 9:30 am while things were still cold. Much evidence of the recent wind event in the alpine with widespread wind slabs ranging in thickness from an inch to feet. There was some natural avalanche activity on the peak south of mt Bole. 
 

Got an ECTN 19 and 23 on a SE aspect at 9300’ HS 95cm

This was on a thin layer of facets sitting under a crust at 58cm. With a few prior hand pits showing planar shear on this layer we opted to keep it low angle.

By noon things were getting quite warm and Skiing through the thinly covered, glopy bushwhack back to the trail was our crux for the day. 

Region
Northern Gallatin
Location (from list)
Maid of the Mist

Buck Ridge

Date
Activity
Snowmobiling

Snow rangers went as far as 3rd Yellowmule. We saw no new snow but evidence of wind effect, including a sizable, probable windslab avalanche Top of Macattee Basin

Region
Northern Madison
Location (from list)
Buck Ridge
Observer Name
Sandy Jett

GNFAC Avalanche Forecast for Sat Dec 21, 2024

Snowpack and Avalanche Discussion

<p><span><span><span><span><span><span>Large </span></span></span></span></span></span><span><span><span><strong><span><span>Persistent Slab avalanches </span></span></strong></span></span></span><span><span><span><span><span><span>have been breaking on weak layers in the middle of the snowpack and near the ground (</span></span></span></span></span></span><a href="https://www.youtube.com/watch?v=zCdhitUHk1o"><span><span><span><strong>…;, </span></span></span></span></span></span><a href="https://www.mtavalanche.com/images/24/large-persistent-slab-avalanche-h… photo</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/persistent-slab-avalanche-fisher"… photo</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>). If you get onto a steep slope today, expect to trigger a similar slide. These slides can be triggered from below, so be cautious passing beneath steep slopes as well.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>The first big loading event of the season only ended 48 hours ago. Persistent weak layers are widespread - these weak layers (surface hoar and facets) often remain easily triggered for a couple days after a loading event ends and we expect that to be true today.&nbsp;</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Human triggered avalanches are likely and the avalanche danger is CONSIDERABLE. Choose slopes sheltered from the wind, less than 30 degrees steep, without steeper slopes above, for good, safe riding today.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Across the rest of our advisory area, triggering, large, dangerous avalanches is still possible, but they have become a bit less likely. The bulk of the last snowfall event had wrapped up by Monday night. High winds on Wednesday drifted lots of snow (</span></span></span></span></span></span><a href="https://www.youtube.com/watch?v=w-aXzlPHrYA"><span><span><span><span><s… video</span></span></u></span></span></span></span></span></a><span><span><span><span><span><span>), but the snowpack has now had a few days break from loading.</span></span></span></span></span></span></p>

<p><span><span><span><strong><span><span>Persistent Slab avalanches </span></span></strong></span></span></span><span><span><span><span><span><span>remain a serious concern. Weak layers are widespread in the middle of the snowpack and earlier this week we saw avalanches breaking on them. On Tuesday, I triggered a slide from 200 ft away on Buck Ridge (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/32497"><span><span><span><strong><span…;). On Wednesday, an avalanche on Saddle Peak broke 1-3 feet deep, and ran 1500 vertical feet (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/32548"><span><span><span><strong><span…;). A large collapse yesterday in the Bridger’s reminds us that similar slides remain possible (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/32582"><span><span><span><strong><span…;).</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Minimize potential consequences by choosing smaller slopes with clean runouts if you decide to get into steeper terrain today. Stay alert for signs of instability (cracking, collapsing, or poor test results).&nbsp;</span></span></span></span></span></span></p>

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

Upcoming Avalanche Education and Events

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Recent large avalanches near Cooke

Date
Activity
Snowmobiling

We rode out to Lulu Pass to look at the few avalanches that were reported yesterday on Henderson and Fisher Mtn. Today we did not see any avalanches that weren't previously reported, other than one small, but thick wind slab on south facing slope of Scotch Bonnet (photo). At least the avalanche on Fisher and one on Henderson broke near the ground (pics attached). Some slides were heavily refilled by drifted snow, so it was hard to tell how deep they broke.

Yesterday I saw a wide slab avalanche up on west Woody Ridge from town (photo attached). It happened late on Wednesday or overnight during or after the strong winds and snowfall.

We dug a pit on a north-northeast facing slope below Fisher Mtn. (on Rob's Knob). Snowpack was just over 3 feet deep with a stripe of surface hoar in the middle. Generally 1F to Pencil hard slab above the SH. Facets near the ground were 2-3mm and rounding. We had ECTP22 on the surface hoar and ECTN22 and PST 25/100arr.

Despite the generally hard and rounded facets near the ground, recent avalanches are a sign that those are a problem in addition to the surface hoar.

Clear and mostly calm today. A few rollerballs on southwest aspects.

Overall, the recent avalanche activity is a sign that the early season weak layers are a problem to watch going forward. Danger and likelihood of avalanches may decrease in the immediate future with a break from loading, but we need to be thinking about these layers when future storms add up.

Region
Cooke City
Location (from list)
Fisher Mtn.
Observer Name
Alex Marienthal