22-23

The Throne - Cracking and Wind Loading

Date
Activity
Skiing
Snowmobiling

We rode into The Throne, and skinned up the ridge. While skinning we saw cracks in front of our skis in the 6” of new snow. The wind was gusting from the north most of the day–our skin track was filled in by the time we skied out. Where we dug, HS was 130 cm (~4 feet) on the NE aspect at 8,100 feet. ECTN 8 on the new snow, and ECTN 24 at a layer of graupel about 1 foot down from the surface. This layer was noted by skiers in Texas Meadows yesterday.

While skiing back to our sleds we triggered a small slide in a wind loaded pocket of snow on a ~35º, isolated terrain feature (SS-ASu-R1-D0.5). This was on a southerly aspect, at about 7,000 feet, 4-6” down on surface hoar, 15’ wide, 30’ vertical run.


 

Region
Bridger Range
Location (from list)
The Throne
Observer Name
Ian Hoyer, Alex Haddad

GNFAC Avalanche Forecast for Fri Jan 6, 2023

Snowpack and Avalanche Discussion

<p><span><span><span><span><span><span>6 inches of dense new snow with gusty west winds drifting it into thicker slabs make for dangerous avalanche conditions. Plan to avoid wind drifts. Be on the lookout for bulbous pillows of snow below ridgelines or on the side of cross-loaded gullies. Cracks shooting out in front of your skis or sled are a clear sign that you’ve found the unstable snow and should immediately retreat to lower angled slopes. These wind drifts may be sitting on top of freshly buried surface hoar, a weak layer which will make them avalanche more easily, break wider, and be more likely to break above you (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/images/23/surface-hoar-bacon-rind"><span><s…;).</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>This load of new snow also makes slides breaking deeper in the snowpack more likely. You may not get any feedback from the more deeply buried weak layers until it is too late. Tone down your terrain choices, because if one of these slides breaks, it will be large and likely not survivable (</span></span></span></span></span></span><a href="https://www.youtube.com/watch?v=8T2VFhPHOV4"><span><span><span><strong>… Peak video</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>). The avalanche danger is CONSIDERABLE today on wind loaded slopes in the Bridger Range and MODERATE on all other slopes.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Elsewhere throughout the advisory area we have weak layers buried in the snowpack with a few inches of new snow on top. Small slides in the new snow are possible, especially in wind drifts, but slides breaking deep are the major concern. Last weekend, when these weak layers were last loaded there were both natural and human triggered avalanches (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/27422"><span><span><span><strong><span… and details of fatal avalanche in Cooke</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>). Several of these slides broke on the sides of steep gullies above terrain traps, good motivation to give these small slopes plenty of respect (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/27487"><span><span><span><strong><span…;, </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/27490"><span><span><span><strong><span…;, </span></span></span></span></span></span><a href="https://youtu.be/ekL311py9yE"><span><span><span><strong><span><u><span>…;). Many of these avalanches were triggered from thinner areas on a slope. Similar avalanches are possible today.&nbsp;</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Mitigate these lurking instabilities by looking for signs of instability (recent avalanches, cracking, collapsing, poor test scores) and avoiding steep slopes if you find them. Only expose one person at a time to steep slopes, watch your partner from a safe spot, and make sure everyone is carrying avalanche rescue gear (beacon, shovel, probe).</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>For today, since avalanches are possible, the avalanche danger is rated MODERATE in the Madison and Gallatin Ranges, Lionhead area, and mountains around Cooke City.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>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).&nbsp;</span></span></span></span></span></span></p>

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From email: "I came across this older avalanche yesterday when I was guiding a group in the Kirkwood area, it’s an area in the Cabin Creek drainage. It looked to be an older natural slide probably just after the last storm cycle a few days to almost a week ago now. North, North East Aspect. Approximately 39 degree slope (Because of a creek with open water just below the slide, I couldn’t get close enough to accurately measure the slope)". Photo: J. Norlander

 

 

 

Southern Madison, 2023-01-06

Older natural avalanche

Date
Activity
Snowmobiling

I came across this older avalanche yesterday when I was guiding a group in the Kirkwood area, it’s an area in the Cabin Creek drainage. It looked to be an older natural slide probably just after the last storm cycle a few days to almost a week ago now. After seeing the old slide and taking a look we found a safe slope with the same aspect approximately 300 yards away with the same NNE aspect, dug a pit and did an ECT test with stabile results.

Kirkwood

North, North East Aspect

Approximately 39 degree slope (Because of a creek with open water just below the slide, I couldn’t get close enough to accurately measure the slope)

ECTX…When digging the pit we could see what looked like 2 weak layers in the snow pack and a faceted layer at the ground. We had no failures during the test and even after the test when I pulled and pried with a shovel, the snow held together and showed signs of stability.

 

Region
Southern Madison
Location (from list)
Cabin Creek
Observer Name
Jim Norlander