23-24

Large Avalanche on Scotch Bonnet

Date

Avoiding avalanche terrain remains our risk mitigation strategy in Cooke City (2/18). We investigated a large avalanche on the north side of Scotch Bonnet that ran 400 vertical feet, broke 400 feet wide, and failed 5 feet deep. You would need to get lucky to survive getting caught in a slide that size, and triggering them is likely on slopes steeper than 30 degrees. There was a small avalanche on a steep rollover below the toe of the debris. Digging in their flank and crown, respectively, we found that they both failed on the layer of surface hoar. This was interesting in that there was well-preserved surface hoar at upper elevation slopes often exposed to the wind. However, the actual failure point is somewhat irrelevant, given the multiple weak layers in close proximity within the snowpack. 

Region
Cooke City
Location (from list)
Scotch Bonnet
Observer Name
David Zinn

Natural avalanche south of Flanders

Date
Activity
Skiing

Toured up to Flanders today. Variable snow but stable conditions on the main route to the SE Bowl. Large natural avalanche on the NE face south of Flanders. 

Region
Northern Gallatin
Location (from list)
Flanders Creek

A dozen recent avalanches at Buck Ridge

Date
Activity
Snowmobiling

We rode out Buck Ridge to Muddy Creek and towards Cedar Mtn.. We went to look at the large avalanches riders remotely triggered yesterday. In addition to three previously reported avalanches, we saw at least eight recent avalanches that were not previously reported and appeared to have occurred at various times over the last 1-3 days, natural and/or remote triggered by riders. A group in the parking lot mentioned seeing many slides actively happen in this area on Friday, and a couple slides looked crisp enough to have occurred within the last 12-24 hours. We saw at least six recent slides in Muddy Creek, two in McAtee Basin, and one in Second Yellow Mule. Most were 2-3' deep hard slabs, ranging from 50'-500' wide.

We also saw a fresh avalanche that we either triggered from 750-800 feet away or it broke naturally. This avalanche happened when we were riding near the larger of the two avalanches from yesterday, on the south side of Cedar Mtn. When we regrouped at the base of the recent avalanche I was scanning all the nearby slopes and did not see any fresh avalanches, and noted a huge cornice on a low convex slope. We then rode up and parked near the top of yesterday's slide, and Doug noticed a fresh slide on the slope I had just been starring at. It was a wind-loaded slope, actively loading. The avalanche was ~130' wide with 100' of 4-12" deep new snow/wind slab and 30' wide broke almost 3 feet deep on weak snow near the ground.

Skies were overcast to partly sunny. Wind was light to moderate from the southwest-west. It snowed lightly on and off all day. There was about 1" of new snow at noon at 9,000'.

All the recent large avalanches and a freshly triggered avalanche are clear signs that the snowpack is dangerous and people should avoiding riding on and below steep slopes.

Region
Northern Madison
Location (from list)
Buck Ridge
Observer Name
Alex Marienthal

Test scores below bradley’s meadow

Date
Activity
Skiing
Snowboarding

NE aspect, 7400 ft. ECTP 14. PST 25/100

Region
Bridger Range
Location (from list)
Bradley Meadow
Observer Name
Noah Daily

Large avalanche on east facing aspect

Date
Activity
Skiing

From woody ridge, we observed a large avalanche across the republic creek drainage (not sure what the peak is called but see the coordinates). I heard it first since it sounded like thunder or a plane, and then saw a huge cloud of snow moving down the mountain across the drainage.  We do not know if it was natural or triggered by someone.

We also observed large collapsing and whumpfing at the top of woody ridge on wind loaded slopes. Nothing moved as it was less than 30 degrees. 

 

Region
Cooke City
Location (from list)
Republic Creek
Observer Name
Becca Huyard

Test results anh whumphing

Date
Activity
Skiing

We dug on southern at 9200 ft  and got ECTN, however as we skinned up on the west side we noticed a little bit of whumphing and we noticed some collapsing while skiing small roll overs on the east aspect. 

Region
Northern Madison
Location (from list)
Bear Basin

GNFAC Avalanche Forecast for Sun Feb 18, 2024

Snowpack and Avalanche Discussion

<p><span><span><span><span><span><span>Stay off avalanche terrain today to avoid being caught in a large, potentially deadly avalanche. Over the last two days there were multiple close calls, natural avalanches, and avalanches triggered remotely from flat terrain hundreds of feet away, clearly showing us the snowpack is very unstable.</span></span></span></span></span></span></p>

<ul>
<li><span><span><span><span><span><span>Yesterday in Taylor Fork a rider triggered a slide, was caught, deployed their airbag, got partially buried, and luckily was uninjured (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/30839"><span><span><span><strong><span…;).</span></span></span></span></span></span></li>
<li><span><span><span><span><span><span>Near Big Sky, a skier triggered a large avalanche and was luckily not caught (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/30843"><span><span><span><strong><span…;), and riders near Cedar Mtn. triggered two big avalanches from flat terrain far below with one of the slides breaking up to 10-12’ deep (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/30818"><span><span><span><strong><span…;, </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/30819"><span><span><span><strong><span…;).</span></span></span></span></span></span></li>
<li><span><span><span><span><span><span>Another close call occurred on Friday near Cooke City. A rider triggered an avalanche on the north side of Scotch Bonnet which broke 2-4 feet deep and hundreds of feet wide, and nobody was caught (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/30780"><span><span><span><strong><span…;).&nbsp;</span></span></span></span></span></span></li>
<li><span><span><span><span><span><span>On Friday, riders in Portal Creek remotely triggered four avalanches from up to 900 ft away (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/30799"><span><span><span><strong><span…;), and near Lionhead Ian and I saw a slide that happened during the day, remotely triggered by riders from 150 ft away in a flat meadow above (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/30792"><span><span><span><strong><span…;).&nbsp;</span></span></span></span></span></span></li>
<li><span><span><span><span><span><span>On Thursday, Dave dug a snowpit in Bear Basin and got unremarkable test results but advised ignoring them because of the big picture signs of instability (</span></span></span></span></span></span><a href="https://www.youtube.com/watch?v=5KoxeBr3WRI"><span><span><span><strong>…;). That night, a natural avalanche broke only a couple hundred feet away from his snowpit (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/30796"><span><span><span><strong><span…;).</span></span></span></span></span></span></li>
<li><span><span><span><span><span><span>Yesterday another large fresh natural avalanche was reported by riders on Buck Ridge (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/30836"><span><span><span><strong><span…;).</span></span></span></span></span></span></li>
</ul>

<p><span><span><span><span><span><span>The mountains are yelling at us to stay off of and out from underneath slopes steeper than 30 degrees. Plan your routes carefully. Don’t trust the snowpack, even if you don’t see obvious signs of instability such as collapsing, nearby avalanches, or poor test scores. The overwhelming amount of avalanches and collapsing throughout the forecast area over the last month and a half cannot be ignored (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/weather/wx-avalanche-log"><span><span><span… and weather log</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>Moderate to strong winds overnight and today will drift snow into thicker slabs which will make wind-loaded slopes easier to trigger and possibly break naturally. Either way, weak sugary snow at the base of the snowpack makes it likely for a person to trigger a large avalanche on all steep slopes today, whether wind-loaded or not. Dangerous avalanche conditions exist and the avalanche danger is CONSIDERABLE.</span></span></span></span></span></span></p>

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