23-24

Cooke City, unstable snowpack

Date

Skied south of Cooke City today.  LOTS of collapsing and cracking. (maybe 30 good collapses throughout the day)  Felt confident that one could have easily triggered an avalanche today if they wanted to.  

New snow:  about 10cms more last night.  Warmer temps, so the new snow was slightly upside down from the weekend's fresh snow.

ECTP2 on a west aspect at 9200'.  Snowpit attached.  

New/ old snow interface is the layer of primary concern.  (persistent slab problem)

No avalanche activity observed.  

Region
Cooke City
Observer Name
Beau Fredlund

Reactive on east aspects

Date
Activity
Skiing

Lots of cracking and collapsing on skin track and ski cuts were reactive on steeper slopes. Dug on NE slope 9640'. HS 110cm ECTN 12 & ECTN 14 40cm down.  

Region
Cooke City
Location (from list)
Lulu Pass
Observer Name
Reed Youngbar

Hyalite Gully Wind Slabs

Date
Activity
Ice Climbing

Climb above Dribbles today. No surprise but where yesterday/last nights new snow has been drifted onto old snow, there is a wind slab problem. We found this combo in gullys above 8000 ft, slab depths to 50 cm, interface is 1-2mm FC. There are also graupel layers within the new snow that were reactive but less concern about those. We experienced numerous collapses and triggered a size 1 pocket that moved 6 in downhill. Just needs a steeper slope angle or a bit more slab and things will get interesting. 
 

Big picture with all the kooks coming to town for icefest it’s kind of funky conditions up there right now, lots of bare ice/rock making for a fall hazard in many places we normally don’t, and poor structure in the gullys, especially higher up. You can go from bare rock/ice to 1.5 m snow in just a couple steps. With continued wind and/or precip things could get active.

 

Region
Northern Gallatin
Location (from list)
Hyalite - main fork

GNFAC Avalanche Forecast for Mon Dec 4, 2023

Snowpack and Avalanche Discussion

<p><span><span><span><span><span><span>While Dave and his partner were digging a pit on Lionhead Ridge yesterday, unbeknownst to him, a party of 3 splitboarders “kicked off a good slide in a NE facing chute” as the first person descended (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/29357"><span><span><span><strong><span…;). On the approach, both Dave and the boarders separately had small whumpfs and cracking. In his pit, Dave found weak and sugary snow under a slab of new and winbblown snow. His stability test fractured ridiculously easy (ECTP1). His </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/29345"><span><span><span><strong><span… and observation</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span> mirror the snowpack the splitboarders triggered. Luckily, they were going one at a time, no one was caught, and the party had rescue gear. Although they were extremely disappointed in their decision making, they modeled good travel protocol which paid safety dividends.&nbsp;</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>The snowpack in Cooke City is not much better. New snow and wind-loading have created instability. Skiers noted a natural avalanche on east Henderson (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/images/23/natural-avalanche-east-henderson"…;) and 2 parties had cracking and whumpfing as they toured (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/29355"><span><span><span><strong><span… Mine ob</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/29347"><span><span><span><strong><span… ob</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>).</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>The snowpack structure is weak and unstable. Whumpfs and shooting cracks under our feet are a sure sign that we can trigger a slide. Given the late start to the ski season we are hungry to get out there, but need to reign in our enthusiasm. The boarder’s self assessment of their near-miss is valuable. He writes, “My thought was that it was slightly questionable but manageable if mitigated and ridden carefully, which was stupid reasoning, we all kinda agreed on that and&nbsp; dove into a sketchy situation, which ended up being a close call.” </span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>In the last 4 days the mountains around Bozeman received around 5” of snow with the Big Sky area and southern Madison and southern Gallatin Ranges getting 12-15”.&nbsp; This snow was blown into wind slabs that overlay weaker, faceted snow found at higher elevations (around 9,000’). </span></span></span></span></span></span><a href="https://www.youtube.com/watch?v=khUlf_rurog"><span><span><span><strong>…’s video</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span> from the Yellowstone Club gives us a first hand look at this weak and unstable structure.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>On Saturday, I found a thin wind crust easily cracking up Hyalite (</span></span></span></span></span></span><a href="https://mtavalanche.com/node/29337"><span><span><span><strong><span><u>…;) and skiers at Bridger Bowl saw the same (</span></span></span></span></span></span><a href="https://mtavalanche.com/node/29336"><span><span><span><strong><span><u>…;). The snowpack is thin and avalanche risk will likely be confined to wind-loaded gullies or bowls. Ice climbers need to be careful of triggering small pockets of drifted snow. Skiers should heed the sage advice, “It’s there’s enough snow to ski, there’s enough snow to avalanche”. </span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>The snowpack in Island Park (IP), West Yellowstone and Cooke City is similar. New snow and wind-loading have created dangerous avalanche conditions.&nbsp; Evidence includes a lot of slides in Black Canyon outside IP, </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/29357"><span><span><span><span><span><… snowboarder triggered avalanche in Lionhead</span></span></u></span></span></span></span></span></a><span><span><span><span><span><span>, </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/29347"><span><span><span><span><span><… natural slide outside Cooke City and skiers getting whumping and cracking as they toured</span></span></u></span></span></span></span></span></a><span><span><span><span><span><span>. Avalanches, cracks and collapses warn us to not enter avalanche terrain. Carry avalanche rescue gear (beacon, shovel, probe) and make sure your gear and skills are in working order.</span></span></span></span></span></span></p>

Upcoming Avalanche Education and Events

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Splitboarder triggered avalanche at lionhead

Lionhead Ridge
Lionhead Range
Code
SS-ARu-R2-D2-O
Elevation
9000
Aspect
NE
Latitude
44.71450
Longitude
-111.31800
Notes

Was splitboarding up near lions head ridge today. Made some bad decisions and kicked off a good slide in a NE facing chute. Was with 2 buddies, 1 of which skied the line 3 weeks ago.  Underneath about a foot of new powder snow there was a firm crust that seemed like it was old  hard windslab in the gut of the chute, and I think a sun crust on the riders left side(East aspect). We had 2 spots where we were planning to re group at, first was a small cubby area right before a slight rollover about 75 ft from the top. I dropped first, made some turns down toward the pulloff, as I pulled in, I triggered a good size slab that propagated maybe 40-50 ft across, at the rollover as I carved into the pulloff.  Pulled  all snow  out of the chute down to the ground. Seemed to have failed on sugary facets on ground/ice crust close to the ground... 

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Soft slab avalanche
Trigger
Snowboarder
Trigger Modifier
u-An unintentional release
R size
2
D size
2
Bed Surface
O - Old snow
Problem Type
Persistent Weak Layer
Slab Thickness
10.0 inches
Slab Width
45.00ft
Slab Thickness units
inches
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

Splitboarder triggered avalanche at lionhead

Date
Activity
Snowboarding

Was splitboarding up near lions head ridge today. Made some bad decisions and kicked off a good slide in a NE facing chute. Was with 2 buddies, 1 of which skied the line 3 weeks ago.  Underneath about a foot of new powder snow there was a firm crust that seemed like it was old  hard windslab in the gut of the chute, and I think a sun crust on the riders left side(East aspect). We had 2 spots where we were planning to re group at, first was a small cubby area right before a slight rollover about 75 ft from the top. I dropped first, made some turns down toward the pulloff, as I pulled in, I triggered a good size slab that propagated maybe 40-50 ft across, at the rollover as I carved into the pulloff.  Pulled  all snow  out of the chute down to the ground. Seemed to have failed on sugary facets on ground/ice crust close to the ground... 

Region
Lionhead Range
Location (from list)
Lionhead Ridge

Cooke City 15-20 cm @ 8,000 ft

Date
Activity
Skiing

I skied the E. facing meadows above the Erma Mine. 15 -20 cm new snow in meadows.

Cloudy and cool teens F. calm.

Good skinning/skiing on supportable m/f crust below new snow. This layer was quite reactive with cracking/sliding on steep side gully features.

Region
Cooke City
Observer Name
Jesse Logan